- Email: [email protected]
Molecular Heterogeneity of Epidermolysis Bullosa Simplex: Contribution of EXPH5 Mutations
M Pigors et al. Contribution of EXPH5 Mutations
comprehensive cancer registries, did not increase (Holterhues et al., 2010). The strength of our study lies in the use of population-based data, which provide a large sample size with enough statistical power to conduct incidence analyses. In addition to the aforementioned registration issues, another limitation is underreporting. Four to six percent of CLs categorized as CTCL in the SEER database were found to have B-cell lineage under the SEER variable ‘‘grade’’ (Criscione and Weinstock, 2007; Imam et al., 2013). In addition, the rarity of CBCL makes trend evaluation over time difficult. A third significant limitation is that CBCL can represent primary versus secondary skin involvement. Although cases were counted using anatomic sites coded for skin, it was difficult to distinguish whether these patients had codes of skin only (primary skin involvement) or had non-skin sites in addition (secondary skin involvement). Thus, there
is likely a mix of patients with primary versus secondary skin involvement. In conclusion, we report a stabilization of overall CBCL incidence. The causes for this trend change are unknown but may include issues with registration in the early years of SEER. Further investigation is warranted to determine the true etiologies of this finding. CONFLICT OF INTEREST The authors state no conflict of interest.
Kaveri Korgavkar1,2 and Martin A. Weinstock1,2,3,4 1
Department of Dermatology, Brown University, Providence, Rhode Island, USA; 2 Dermatoepidemiology Unit, Veterans Affairs Medical Center, Providence, Rhode Island, USA; 3Department of Epidemiology, Brown University, Providence, Rhode Island, USA and 4 Department of Dermatology, Rhode Island Hospital, Providence, Rhode Island, USA E-mail: [email protected]
REFERENCES Bradford P, Devesa S, Anderson W et al. (2009) Cutaneous lymphoma incidence patterns in the United States: a population-based study of 3884 cases. Blood 113:5064–73 Criscione V, Weinstock M (2007) Incidence of cutaneous T-cell lymphoma in the United States, 1973-2002. Arch Dermatol 143: 854–9 Holterhues C, Vries E, Louwman M et al. (2010) Incidence and trends of cutaneous malignancies in the Netherlands, 1989–2005. J Invest Dermatol 130:1807–12 Imam M, Shenoy P, Flowers C et al. (2013) Incidence and survival patterns of cutaneous T-cell lymphomas in the United States. Leuk Lymphoma 54:752–9 Smith B, Smith G, Cooper D et al. (2005) The cutaneous B-cell lymphoma prognostic index: a novel prognostic index derived from a population-based registry. J Clin Oncol 23:3390–5 Willemze R (2012) Thirty years of progress in cutaneous lymphoma research. G Ital Dermatol Venereol 147:515–21 Willemze R, Jaffe E, Burg G et al. (2005) WHOEORTC classification for cutaneous lymphomas. Blood 105:3768–85
Molecular Heterogeneity of Epidermolysis Bullosa Simplex: Contribution of EXPH5 Mutations Journal of Investigative Dermatology (2014) 134, 842–845; doi:10.1038/jid.2013.373; published online 17 October 2013
TO THE EDITOR Epidermolysis bullosa simplex (EBS) is a group of genetic mechanobullous disorders characterized by intraepidermal cleavage. In the vast majority of cases, basal EBS is caused by dominantly inherited mutations in the keratin-5 and -14 genes (KRT5 and KRT14). However, the disease is genetically heterogeneous with about 25–30% of patients lacking mutations in those genes (Rugg et al., 2007; Bolling et al., 2011; Bruckner-Tuderman and Has, 2012). Well-defined subtypes of EBS are associated with typical clinical features and molecular pathology, but patients with mild skin fragility often exhibit less characteristic features rendering the determination of the candidate gene
difficult (Groves et al., 2010; Liu et al., 2012; Pigors et al., 2012; Kiritsi et al., 2013). Recently, a homozygous frameshift mutation in the exophilin-5 gene (EXPH5) was identified in three individuals of a consanguineous Iraqi family with mild skin fragility (McGrath et al., 2012). EXPH5 encodes the Rab27 effector protein called synaptotagminlike protein lacking c2 domains b (Slac2b). This protein, also called exophilin-5, is involved in intracellular protein transport and exosome secretion (Ostrowski et al., 2010). The mutation found in the Iraqi family was located in exon 6 of EXPH5, close to the 30 end, leading to a premature termination codon and the absence of the Slac2b protein in the patient’s skin as shown by
Abbreviations: EBS, epidermolysis bullosa simplex; EXPH5, exophilin-5 gene; KRT5, keratin-5 gene; KRT14, keratin-14 gene; Slac2b, synaptotagmin-like protein lacking c2 domains b Accepted article preview online 4 September 2013; published online 17 October 2013
842
Journal of Investigative Dermatology (2014), Volume 134
immunolabeling with an antibody recognizing the C terminus of Slac2b. The clinical phenotype included discrete trauma-induced skin blistering, erosions and hemorrhagic crusting, mild atrophy, and hypopigmentation. This first case report prompted us to sequence EXPH5 in a cohort of 35 patients with clinically suspected EBS but without mutations in the KRT5 and KRT14 genes. Here, we report the second family with two EXPH5 mutations and extend on the clinical and morphological spectrum of this rare autosomal recessive EBS. After obtaining written informed consent, genomic DNA was extracted from EDTA–blood samples obtained from 35 individuals and, whenever possible, from their parents for mutation analysis. Amplification and sequencing of KRT5 and KRT14 were performed as described previously (Arin et al., 2010). Primers for all six exons and
M Pigors et al. Contribution of EXPH5 Mutations
At birth
6 Months old
15 Months old
Figure 1. Clinical findings of exophilin-5 (EXPH5)-associated epidermolysis bullosa simplex. (a) Pedigree with the index patient indicated by a black circle. (b) At birth, the index patient presented with large erosions, in particular, on the legs. (c and d) Between 6 (c) and 15 (d) months of age, the main clinical features encompassed small blisters and erosions (arrows) as well as linear and hemorrhagic crusts (arrowheads) on the extremities.
exon/intron boundaries of EXPH5 were designed using Primer 3 software (NM_015065.2, Supplementary Table S1 online). Mutation analysis was performed as described (Pigors et al., 2011). The project was approved by the ethics committee of the University of Freiburg and was conducted according to the Declaration of Helsinki Principles.
Among the 35 patients suspected with EBS, but lacking genetic defects in KRT5 or KRT14, EXPH5 mutations were disclosed in a single case. The female index patient was the only affected member of the family (Figure 1a). Her parents were of German origin, and consanguinity was not known in the family. The index patient was born at
term after an uncomplicated pregnancy by cesarean section because of breech presentation. At birth, she presented with extensive erosions on the lower legs, thorax, and upper arm that covered about 20% of the body surface (Figure 1b). The lesions healed rapidly and without any residual manifestations. During the follow-up visits between www.jidonline.org
843
M Pigors et al. Contribution of EXPH5 Mutations
Control
Control
Patient: c.1395delC
Patient: c.2897delC
c.1395delC
1
2 3
4
5
c.2897delC
c.5786delC
6
Patient
Keratin-14
Control
* * *
Figure 2. Exophilin-5 (EXPH5) mutations lead to cleavage within the basal layer of the epidermis. (a) Two EXPH5 frame-shift mutations, c.1395delC and c.2897delC (arrows), were disclosed in the patient. (b) Schematic representation of the EXPH5 gene. Blue boxes represent the exons. The variants, indicated in red, are located in exon 6. The previously identified variant is shown in black (McGrath et al., 2012). (c) Immunofluorescence staining of keratin-14 showed several splits in the basal layer of the epidermis (asterisks). Scale bar ¼ 20 mm. (d) Histopathological analysis revealed discrete hyperkeratosis and macro (left panel) and micro blisters (right panel) along the dermal–epidermal junction. Scale bar ¼ 50 mm.
6 and 15 months of age, small, traumainduced serous blisters, recurrent erosions, and crusts were observed predominantly on the extremities (Figure 1 c and d). There was no evidence of scarring or pigment anomalies. Mucous membranes, nails, and hair were not affected. Currently, at the age of 2 years, the patient is in a good general condition and occasionally develops blisters at sites of mechanical trauma. Mutation analysis of the index patient’s DNA revealed compound heterozygosity for two EXPH5 1-base-pair deletions, c.1395delC, p.F466Lfs*44 and c.2897delC, p.P966Lfs*11 (Figure 2a). Both parents were carriers, each harboring one of the two mutations. As a consequence of the deletions, frameshifts in codons 466 and 966 occurred and created a premature termination of translation after 44 and 11 amino acids, respectively. The mutations are located within the large exon 6 of EXPH5, upstream of the previously reported mutation, c.5768delC (Figure 2b; McGrath et al., 2012). To the best of our knowledge, the two variants have not been reported before (HGMD Professional 2013.1). Both were 844
excluded in 100 normal control individuals of German origin. A skin biopsy from the upper leg of the index patient was obtained at the age of 10 days and subjected to indirect immunofluorescence staining with antibodies to plectin, BPAG-1e, integrin a6 and b4 subunits, collagen XVII, laminin332, collagen IV, and collagen VII (Herz et al., 2006; Kiritsi et al., 2013). No abnormalities in the expression of these markers at the dermal–epidermal junction were observed. All markers stained at the blister floor and immunolabeling with an antibody to keratin-14 (clone LL002, Abcam) revealed several clefts within the basal keratinocyte layer (Figure 2c). A hematoxylin and eosin staining showed multiple macro and micro blisters at the dermal–epidermal junction and mild hyperkeratosis (Figure 2d). This EBS subtype seems to be very rare, as it represents less than 1% of the patients with EBS in our cohort (1 in 140). The particular features of the present case followed from birth over the first 2 years of life allow for a better definition of the clinical and morphological characteristics of this entity. The EXPH5 frame-shift mutations led to
Journal of Investigative Dermatology (2014), Volume 134
congenital skin fragility. In contrast to extensive erosions at birth, which were associated with significant cleavage within the basal epidermal layer, skin fragility improved within the first 2 years of life, and mechanically induced, small blisters and erosions as well as linear and hemorrhagic crusts were the main features. The mutations disclosed here are very likely to alter the expression of the protein significantly. Considering the central location of the two mutations within the molecule, it is highly probable that they might lead to complete loss or truncation of Slac2b, which explains the severity of the congenital skin fragility. No biopsy material was available to further elucidate the consequences of the two mutations on expression of Slac2b. The function of Slac2b in skin is yet poorly understood, but the presence of low intraepidermal blisters supports a role of this molecule in the mechanical stability of basal keratinocytes (McGrath et al., 2012). In summary, this is the second report describing the fourth patient with mutations in the EXPH5 gene. Skin fragility was prominent at birth but manifested later as small blisters, erosions, and crusts predominantly on the extremities after
C Has et al. Missense Mutation p.R1303Q in Type XVII Collagen
mechanical trauma. In contrast to the previous report, in which the clinicopathologic features were not diagnostic for any particular subtype of epidermolysis bullosa (McGrath et al., 2012), our morphological findings allowed a definite classification as autosomal recessive EBS. CONFLICT OF INTEREST The authors state no conflict of interest.
ACKNOWLEDGMENTS We thank all the patients and in particular the family of the index patient who participated in this study and the physicians who sent samples. The excellent technical support by Vera Morand, Kaethe Thoma, and Annegret Bedorf is gratefully acknowledged. This work was supported by the German Research Foundation grant HA 5663/2-1 to CH, the Network Epidermolysis Bullosa Grant from the Federal Ministry for Education and Research (BMBF) to LB-T, and the Excellence Initiative of the German Federal and State Governments and Freiburg Institute for Advanced Studies, School of Life Sciences to LB-T.
Manuela Pigors1, Agnes Schwieger-Briel1, Juna Leppert1, Dimitra Kiritsi1, Ju¨rgen Kohlhase2, Leena Bruckner-Tuderman1,3 and Cristina Has1
1
Department of Dermatology, University Freiburg Medical Center, Freiburg, Germany; 2 Center for Human Genetics Freiburg, Freiburg, Germany and 3Freiburg Institute for Advanced Studies, University of Freiburg, Freiburg, Germany E-mail: [email protected] SUPPLEMENTARY MATERIAL Supplementary material is linked to the online version of the paper at http://www.nature.com/jid
REFERENCES Arin MJ, Grimberg G, Schumann H et al. (2010) Identification of novel and known KRT5 and KRT14 mutations in 53 patients with epidermolysis bullosa simplex: correlation between genotype and phenotype. Br J Dermatol 162: 1365–9 Bolling MC, Lemmink HH, Jansen GHet al. (2011) Mutations in KRT5 and KRT14 cause epidermolysis bullosa simplex in 75% of the patients. Br J Dermatol 164:637–44 Bruckner-Tuderman L, Has C (2012) Molecular heterogeneity of blistering disorders: the paradigm of epidermolysis bullosa. J Invest Dermatol 132:E2–5 Groves RW, Liu L, Dopping-Hepenstal PJ et al. (2010) A homozygous nonsense mutation within the dystonin gene coding for the coiled-coil domain of the epithelial isoform of BPAG1 underlies a new subtype of autosomal recessive epidermolysis bullosa simplex. J Invest Dermatol 130:1551–7
Herz C, Aumailley M, Schulte C et al. (2006) Kindlin-1 is a phosphoprotein involved in regulation of polarity, proliferation, and motility of epidermal keratinocytes. J Biol Chem 281:36082–90 Kiritsi D, Pigors M, Tantcheva-Poor I et al. (2013) Epidermolysis bullosa simplex ogna revisited. J Invest Dermatol 133:270–3 Liu L, Dopping-Hepenstal PJ, Lovell PA et al. (2012) Autosomal recessive epidermolysis bullosa simplex due to loss of BPAG1-e expression. J Invest Dermatol 132:742–4 McGrath JA, Stone KL, Begum R et al. (2012) Germline mutation in EXPH5 implicates the Rab27B effector protein Slac2-b in inherited skin fragility. Am J Hum Genet 91: 1115–21 Ostrowski M, Carmo NB, Krumeich S et al. (2010) Rab27a and Rab27b control different steps of the exosome secretion pathway. Nat Cell Biol 12, (Suppl 1–13): 19–30 Pigors M, Kiritsi D, Cobzaru C et al. (2012) TGM5 mutations impact epidermal differentiation in acral peeling skin syndrome. J Invest Dermatol 132:2422–9 Pigors M, Kiritsi D, Krumpelmann S et al. (2011) Lack of plakoglobin leads to lethal congenital epidermolysis bullosa: a novel clinicogenetic entity. Hum Mol Genet 20: 1811–9 Rugg EL, Horn HM, Smith FJ et al. (2007) Epidermolysis bullosa simplex in Scotland caused by a spectrum of keratin mutations. J Invest Dermatol 127:574–80
See related commentary on pg 602
The Missense Mutation p.R1303Q in Type XVII Collagen Underlies Junctional Epidermolysis Bullosa Resembling Kindler Syndrome Journal of Investigative Dermatology (2014) 134, 845–849; doi:10.1038/jid.2013.367; published online 10 October 2013
TO THE EDITOR Hereditary epidermolysis bullosa (EB) comprises a genetically and clinically heterogeneous group of disorders characterized by trauma-induced skin blistering (Fine et al., 2008). EB can be caused by mutations in more than 15 different genes and is classified into four main types according to the level of skin cleavage: EB simplex, junctional EB,
dystrophic EB, and Kindler syndrome (Fine et al., 2008; Bruckner-Tuderman and Has, 2012). Well-defined severe subtypes are associated with typical clinical features and molecular pathology. In contrast, skin biopsies from patients with mild skin fragility often do not exhibit either skin cleavage or abnormalities of dermal–epidermal junction proteins, which hampers determination of the EB
Abbreviations: COL, collagenous domain; COL17A1, collagen XVII gene; EB, epidermolysis bullosa; FERMT1, kindlin-1 gene; NC, non-collagenous domain Accepted article preview online 4 September 2013; published online 10 October 2013
subtype or the candidate gene. In such cases, the precise diagnosis may be difficult and delayed. These phenotypes are associated with missense or splice-site mutations in genes coding for proteins that interact closely in dermal–epidermal adhesion networks (Bruckner-Tuderman and Has, 2012). Here, we report on 15 patients with a distinct phenotype comprising late-onset skin blistering, progressive skin atrophy, loss of dermatoglyphs, scarring, and nail anomalies, accompanied by irregular deposition of basement membrane– associated proteins. www.jidonline.org
845
comprehensive cancer registries, did not increase (Holterhues et al., 2010). The strength of our study lies in the use of population-based data, which provide a large sample size with enough statistical power to conduct incidence analyses. In addition to the aforementioned registration issues, another limitation is underreporting. Four to six percent of CLs categorized as CTCL in the SEER database were found to have B-cell lineage under the SEER variable ‘‘grade’’ (Criscione and Weinstock, 2007; Imam et al., 2013). In addition, the rarity of CBCL makes trend evaluation over time difficult. A third significant limitation is that CBCL can represent primary versus secondary skin involvement. Although cases were counted using anatomic sites coded for skin, it was difficult to distinguish whether these patients had codes of skin only (primary skin involvement) or had non-skin sites in addition (secondary skin involvement). Thus, there
is likely a mix of patients with primary versus secondary skin involvement. In conclusion, we report a stabilization of overall CBCL incidence. The causes for this trend change are unknown but may include issues with registration in the early years of SEER. Further investigation is warranted to determine the true etiologies of this finding. CONFLICT OF INTEREST The authors state no conflict of interest.
Kaveri Korgavkar1,2 and Martin A. Weinstock1,2,3,4 1
Department of Dermatology, Brown University, Providence, Rhode Island, USA; 2 Dermatoepidemiology Unit, Veterans Affairs Medical Center, Providence, Rhode Island, USA; 3Department of Epidemiology, Brown University, Providence, Rhode Island, USA and 4 Department of Dermatology, Rhode Island Hospital, Providence, Rhode Island, USA E-mail: [email protected]
REFERENCES Bradford P, Devesa S, Anderson W et al. (2009) Cutaneous lymphoma incidence patterns in the United States: a population-based study of 3884 cases. Blood 113:5064–73 Criscione V, Weinstock M (2007) Incidence of cutaneous T-cell lymphoma in the United States, 1973-2002. Arch Dermatol 143: 854–9 Holterhues C, Vries E, Louwman M et al. (2010) Incidence and trends of cutaneous malignancies in the Netherlands, 1989–2005. J Invest Dermatol 130:1807–12 Imam M, Shenoy P, Flowers C et al. (2013) Incidence and survival patterns of cutaneous T-cell lymphomas in the United States. Leuk Lymphoma 54:752–9 Smith B, Smith G, Cooper D et al. (2005) The cutaneous B-cell lymphoma prognostic index: a novel prognostic index derived from a population-based registry. J Clin Oncol 23:3390–5 Willemze R (2012) Thirty years of progress in cutaneous lymphoma research. G Ital Dermatol Venereol 147:515–21 Willemze R, Jaffe E, Burg G et al. (2005) WHOEORTC classification for cutaneous lymphomas. Blood 105:3768–85
Molecular Heterogeneity of Epidermolysis Bullosa Simplex: Contribution of EXPH5 Mutations Journal of Investigative Dermatology (2014) 134, 842–845; doi:10.1038/jid.2013.373; published online 17 October 2013
TO THE EDITOR Epidermolysis bullosa simplex (EBS) is a group of genetic mechanobullous disorders characterized by intraepidermal cleavage. In the vast majority of cases, basal EBS is caused by dominantly inherited mutations in the keratin-5 and -14 genes (KRT5 and KRT14). However, the disease is genetically heterogeneous with about 25–30% of patients lacking mutations in those genes (Rugg et al., 2007; Bolling et al., 2011; Bruckner-Tuderman and Has, 2012). Well-defined subtypes of EBS are associated with typical clinical features and molecular pathology, but patients with mild skin fragility often exhibit less characteristic features rendering the determination of the candidate gene
difficult (Groves et al., 2010; Liu et al., 2012; Pigors et al., 2012; Kiritsi et al., 2013). Recently, a homozygous frameshift mutation in the exophilin-5 gene (EXPH5) was identified in three individuals of a consanguineous Iraqi family with mild skin fragility (McGrath et al., 2012). EXPH5 encodes the Rab27 effector protein called synaptotagminlike protein lacking c2 domains b (Slac2b). This protein, also called exophilin-5, is involved in intracellular protein transport and exosome secretion (Ostrowski et al., 2010). The mutation found in the Iraqi family was located in exon 6 of EXPH5, close to the 30 end, leading to a premature termination codon and the absence of the Slac2b protein in the patient’s skin as shown by
Abbreviations: EBS, epidermolysis bullosa simplex; EXPH5, exophilin-5 gene; KRT5, keratin-5 gene; KRT14, keratin-14 gene; Slac2b, synaptotagmin-like protein lacking c2 domains b Accepted article preview online 4 September 2013; published online 17 October 2013
842
Journal of Investigative Dermatology (2014), Volume 134
immunolabeling with an antibody recognizing the C terminus of Slac2b. The clinical phenotype included discrete trauma-induced skin blistering, erosions and hemorrhagic crusting, mild atrophy, and hypopigmentation. This first case report prompted us to sequence EXPH5 in a cohort of 35 patients with clinically suspected EBS but without mutations in the KRT5 and KRT14 genes. Here, we report the second family with two EXPH5 mutations and extend on the clinical and morphological spectrum of this rare autosomal recessive EBS. After obtaining written informed consent, genomic DNA was extracted from EDTA–blood samples obtained from 35 individuals and, whenever possible, from their parents for mutation analysis. Amplification and sequencing of KRT5 and KRT14 were performed as described previously (Arin et al., 2010). Primers for all six exons and
M Pigors et al. Contribution of EXPH5 Mutations
At birth
6 Months old
15 Months old
Figure 1. Clinical findings of exophilin-5 (EXPH5)-associated epidermolysis bullosa simplex. (a) Pedigree with the index patient indicated by a black circle. (b) At birth, the index patient presented with large erosions, in particular, on the legs. (c and d) Between 6 (c) and 15 (d) months of age, the main clinical features encompassed small blisters and erosions (arrows) as well as linear and hemorrhagic crusts (arrowheads) on the extremities.
exon/intron boundaries of EXPH5 were designed using Primer 3 software (NM_015065.2, Supplementary Table S1 online). Mutation analysis was performed as described (Pigors et al., 2011). The project was approved by the ethics committee of the University of Freiburg and was conducted according to the Declaration of Helsinki Principles.
Among the 35 patients suspected with EBS, but lacking genetic defects in KRT5 or KRT14, EXPH5 mutations were disclosed in a single case. The female index patient was the only affected member of the family (Figure 1a). Her parents were of German origin, and consanguinity was not known in the family. The index patient was born at
term after an uncomplicated pregnancy by cesarean section because of breech presentation. At birth, she presented with extensive erosions on the lower legs, thorax, and upper arm that covered about 20% of the body surface (Figure 1b). The lesions healed rapidly and without any residual manifestations. During the follow-up visits between www.jidonline.org
843
M Pigors et al. Contribution of EXPH5 Mutations
Control
Control
Patient: c.1395delC
Patient: c.2897delC
c.1395delC
1
2 3
4
5
c.2897delC
c.5786delC
6
Patient
Keratin-14
Control
* * *
Figure 2. Exophilin-5 (EXPH5) mutations lead to cleavage within the basal layer of the epidermis. (a) Two EXPH5 frame-shift mutations, c.1395delC and c.2897delC (arrows), were disclosed in the patient. (b) Schematic representation of the EXPH5 gene. Blue boxes represent the exons. The variants, indicated in red, are located in exon 6. The previously identified variant is shown in black (McGrath et al., 2012). (c) Immunofluorescence staining of keratin-14 showed several splits in the basal layer of the epidermis (asterisks). Scale bar ¼ 20 mm. (d) Histopathological analysis revealed discrete hyperkeratosis and macro (left panel) and micro blisters (right panel) along the dermal–epidermal junction. Scale bar ¼ 50 mm.
6 and 15 months of age, small, traumainduced serous blisters, recurrent erosions, and crusts were observed predominantly on the extremities (Figure 1 c and d). There was no evidence of scarring or pigment anomalies. Mucous membranes, nails, and hair were not affected. Currently, at the age of 2 years, the patient is in a good general condition and occasionally develops blisters at sites of mechanical trauma. Mutation analysis of the index patient’s DNA revealed compound heterozygosity for two EXPH5 1-base-pair deletions, c.1395delC, p.F466Lfs*44 and c.2897delC, p.P966Lfs*11 (Figure 2a). Both parents were carriers, each harboring one of the two mutations. As a consequence of the deletions, frameshifts in codons 466 and 966 occurred and created a premature termination of translation after 44 and 11 amino acids, respectively. The mutations are located within the large exon 6 of EXPH5, upstream of the previously reported mutation, c.5768delC (Figure 2b; McGrath et al., 2012). To the best of our knowledge, the two variants have not been reported before (HGMD Professional 2013.1). Both were 844
excluded in 100 normal control individuals of German origin. A skin biopsy from the upper leg of the index patient was obtained at the age of 10 days and subjected to indirect immunofluorescence staining with antibodies to plectin, BPAG-1e, integrin a6 and b4 subunits, collagen XVII, laminin332, collagen IV, and collagen VII (Herz et al., 2006; Kiritsi et al., 2013). No abnormalities in the expression of these markers at the dermal–epidermal junction were observed. All markers stained at the blister floor and immunolabeling with an antibody to keratin-14 (clone LL002, Abcam) revealed several clefts within the basal keratinocyte layer (Figure 2c). A hematoxylin and eosin staining showed multiple macro and micro blisters at the dermal–epidermal junction and mild hyperkeratosis (Figure 2d). This EBS subtype seems to be very rare, as it represents less than 1% of the patients with EBS in our cohort (1 in 140). The particular features of the present case followed from birth over the first 2 years of life allow for a better definition of the clinical and morphological characteristics of this entity. The EXPH5 frame-shift mutations led to
Journal of Investigative Dermatology (2014), Volume 134
congenital skin fragility. In contrast to extensive erosions at birth, which were associated with significant cleavage within the basal epidermal layer, skin fragility improved within the first 2 years of life, and mechanically induced, small blisters and erosions as well as linear and hemorrhagic crusts were the main features. The mutations disclosed here are very likely to alter the expression of the protein significantly. Considering the central location of the two mutations within the molecule, it is highly probable that they might lead to complete loss or truncation of Slac2b, which explains the severity of the congenital skin fragility. No biopsy material was available to further elucidate the consequences of the two mutations on expression of Slac2b. The function of Slac2b in skin is yet poorly understood, but the presence of low intraepidermal blisters supports a role of this molecule in the mechanical stability of basal keratinocytes (McGrath et al., 2012). In summary, this is the second report describing the fourth patient with mutations in the EXPH5 gene. Skin fragility was prominent at birth but manifested later as small blisters, erosions, and crusts predominantly on the extremities after
C Has et al. Missense Mutation p.R1303Q in Type XVII Collagen
mechanical trauma. In contrast to the previous report, in which the clinicopathologic features were not diagnostic for any particular subtype of epidermolysis bullosa (McGrath et al., 2012), our morphological findings allowed a definite classification as autosomal recessive EBS. CONFLICT OF INTEREST The authors state no conflict of interest.
ACKNOWLEDGMENTS We thank all the patients and in particular the family of the index patient who participated in this study and the physicians who sent samples. The excellent technical support by Vera Morand, Kaethe Thoma, and Annegret Bedorf is gratefully acknowledged. This work was supported by the German Research Foundation grant HA 5663/2-1 to CH, the Network Epidermolysis Bullosa Grant from the Federal Ministry for Education and Research (BMBF) to LB-T, and the Excellence Initiative of the German Federal and State Governments and Freiburg Institute for Advanced Studies, School of Life Sciences to LB-T.
Manuela Pigors1, Agnes Schwieger-Briel1, Juna Leppert1, Dimitra Kiritsi1, Ju¨rgen Kohlhase2, Leena Bruckner-Tuderman1,3 and Cristina Has1
1
Department of Dermatology, University Freiburg Medical Center, Freiburg, Germany; 2 Center for Human Genetics Freiburg, Freiburg, Germany and 3Freiburg Institute for Advanced Studies, University of Freiburg, Freiburg, Germany E-mail: [email protected] SUPPLEMENTARY MATERIAL Supplementary material is linked to the online version of the paper at http://www.nature.com/jid
REFERENCES Arin MJ, Grimberg G, Schumann H et al. (2010) Identification of novel and known KRT5 and KRT14 mutations in 53 patients with epidermolysis bullosa simplex: correlation between genotype and phenotype. Br J Dermatol 162: 1365–9 Bolling MC, Lemmink HH, Jansen GHet al. (2011) Mutations in KRT5 and KRT14 cause epidermolysis bullosa simplex in 75% of the patients. Br J Dermatol 164:637–44 Bruckner-Tuderman L, Has C (2012) Molecular heterogeneity of blistering disorders: the paradigm of epidermolysis bullosa. J Invest Dermatol 132:E2–5 Groves RW, Liu L, Dopping-Hepenstal PJ et al. (2010) A homozygous nonsense mutation within the dystonin gene coding for the coiled-coil domain of the epithelial isoform of BPAG1 underlies a new subtype of autosomal recessive epidermolysis bullosa simplex. J Invest Dermatol 130:1551–7
Herz C, Aumailley M, Schulte C et al. (2006) Kindlin-1 is a phosphoprotein involved in regulation of polarity, proliferation, and motility of epidermal keratinocytes. J Biol Chem 281:36082–90 Kiritsi D, Pigors M, Tantcheva-Poor I et al. (2013) Epidermolysis bullosa simplex ogna revisited. J Invest Dermatol 133:270–3 Liu L, Dopping-Hepenstal PJ, Lovell PA et al. (2012) Autosomal recessive epidermolysis bullosa simplex due to loss of BPAG1-e expression. J Invest Dermatol 132:742–4 McGrath JA, Stone KL, Begum R et al. (2012) Germline mutation in EXPH5 implicates the Rab27B effector protein Slac2-b in inherited skin fragility. Am J Hum Genet 91: 1115–21 Ostrowski M, Carmo NB, Krumeich S et al. (2010) Rab27a and Rab27b control different steps of the exosome secretion pathway. Nat Cell Biol 12, (Suppl 1–13): 19–30 Pigors M, Kiritsi D, Cobzaru C et al. (2012) TGM5 mutations impact epidermal differentiation in acral peeling skin syndrome. J Invest Dermatol 132:2422–9 Pigors M, Kiritsi D, Krumpelmann S et al. (2011) Lack of plakoglobin leads to lethal congenital epidermolysis bullosa: a novel clinicogenetic entity. Hum Mol Genet 20: 1811–9 Rugg EL, Horn HM, Smith FJ et al. (2007) Epidermolysis bullosa simplex in Scotland caused by a spectrum of keratin mutations. J Invest Dermatol 127:574–80
See related commentary on pg 602
The Missense Mutation p.R1303Q in Type XVII Collagen Underlies Junctional Epidermolysis Bullosa Resembling Kindler Syndrome Journal of Investigative Dermatology (2014) 134, 845–849; doi:10.1038/jid.2013.367; published online 10 October 2013
TO THE EDITOR Hereditary epidermolysis bullosa (EB) comprises a genetically and clinically heterogeneous group of disorders characterized by trauma-induced skin blistering (Fine et al., 2008). EB can be caused by mutations in more than 15 different genes and is classified into four main types according to the level of skin cleavage: EB simplex, junctional EB,
dystrophic EB, and Kindler syndrome (Fine et al., 2008; Bruckner-Tuderman and Has, 2012). Well-defined severe subtypes are associated with typical clinical features and molecular pathology. In contrast, skin biopsies from patients with mild skin fragility often do not exhibit either skin cleavage or abnormalities of dermal–epidermal junction proteins, which hampers determination of the EB
Abbreviations: COL, collagenous domain; COL17A1, collagen XVII gene; EB, epidermolysis bullosa; FERMT1, kindlin-1 gene; NC, non-collagenous domain Accepted article preview online 4 September 2013; published online 10 October 2013
subtype or the candidate gene. In such cases, the precise diagnosis may be difficult and delayed. These phenotypes are associated with missense or splice-site mutations in genes coding for proteins that interact closely in dermal–epidermal adhesion networks (Bruckner-Tuderman and Has, 2012). Here, we report on 15 patients with a distinct phenotype comprising late-onset skin blistering, progressive skin atrophy, loss of dermatoglyphs, scarring, and nail anomalies, accompanied by irregular deposition of basement membrane– associated proteins. www.jidonline.org
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