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Hepatic complications of erythropoietic protoporphyria
Pathology (2013) 45(S1), pp. S29–S33
Genetics
HEPATIC COMPLICATIONS OF ERYTHROPOIETIC PROTOPORPHYRIA Pak Leng Cheong1,3, Bing Yu3, Jole Bojovic1,2, Victor Poulos2, Lucinda Freeman1, Peter M. Stewart2, Ronald J. Trent1,3 Departments of 1Molecular & Clinical Genetics, and 2Clinical Chemistry, Royal Prince Alfred Hospital, Sydney, and 3Sydney Medical School, University of Sydney, NSW, Australia Erythropoietic protoporphyria (EPP) is caused by mutations in ferrochelatase (FECH), the last step in the haem biosynthesis pathway. EPP is inherited in a pseudodominant fashion, most commonly due to presence of a low-expression splicing variant IVS3-48C in trans to a disease causing mutation. Reduction in ferrochelatase activity leads to accumulation of protoporphyrin IX (PPIX) and photosensitivity. Hepatotoxicity is a rare complication of EPP, seen in 1–5% of patients.1 Here we present the first reported case of fatal liver failure secondary to EPP in New South Wales, Australia. The patient was found to carry a known mutation (p.Phe260Leu), but IVS3–48C was not detected. The search for additional modifier genes at the genomic level found several potential candidates. These modifier genes may provide an insight on genotype-phenotype correlations in porphyrias. Reference 1. Anstey AV, Hift RJ. Liver disease in erythropoietic protoporphyria: insights and implications for management. Gut 2007; 56: 1009–18.
creatinine kinase was normal on two separate occasions. Subsequently, a mutation in the SHOC2 gene was identified which is thought to explain this child’s phenotype. Conclusion: The array CGH result is possibly an incidental finding as the SHOC2 gene mutation explains this patient’s symptoms. However, given that this duplication involves an X-linked pathogenic gene, clarification of the clinical significance is required to appropriately manage this patient’s family. Unfortunately, testing of other male family members has not been possible at this time. FISH study is unable to precisely determine if the duplication is within or outside of the DMD gene. This case highlights multiple complex issues in array CGH testing including interpretation of duplications and the importance of correlating the patient’s clinical picture with the array CGH result. Questions for Dr Charles (Buck) Strom 1. What is your approach to determining the pathogenicity of duplications in a diagnostic setting when the clinical picture does not match? 2. Questions for How would you suggest the clinician manage and counsel this family?
SEGMENTAL PATERNAL UPD14 – SNP ARRAY SAVES THE DAY?
Question/discussion point for Dr Charles (Buck) Strom 1. The current state of phenotyping cannot match the high throughput of exome/whole genome sequencing. How do we correlate our findings in the genome to phenotype? 2. In trio exome sequencing where the proband has a sibling, what is our obligation to the sibling in terms of incidental findings?
Chiyan Lau1, Val Hyland1, David Young1, Trent Burgess3, Ralph Oertel3, James Harraway2 1Molecular Genetics Laboratory, Division of Haematology, Pathology Queensland, Royal Brisbane and Women’s Hospital, Brisbane, 2Mater Pathology, Brisbane, Qld, and 3VCGS, Melbourne, Vic, Australia
CHALLENGING ARRAY CGH CASE INVOLVING A DUPLICATION OF EXONS 10–18 OF THE DMD GENE IN A BOY WITH NORMAL CREATININE KINASE LEVELS
Background: A baby in neonatal intensive care with respiratory insufficiency, skeletal dysplasia and dysmorphism was clinically suspected to have paternal uniparental disomy of chromosome 14 (UPD14). Molecular testing for UPD14 was requested. Methods: Microsatellite markers on chromosome 14 were genotyped in the affected child and both parents. Standard karyotype and interphase FISH using probes that map to 14qter were performed on the proband. SNP microarray (Illumina HumanCytoSNP-12) was performed on the parent-child trio. Results: Single nucleotide polymorphism (SNP) microarray detected a copy number neutral segment showing loss of heterozygosity (LOH) of approximately 12 Mb in size at the 14q terminus in the proband, encompassing the UPD14 critical imprinted region at 14q32. A SNP trio analysis showed that this segment was of paternal origin only in the proband, while the remainder of chromosome 14 showed biparental inheritance. The results of microsatellite and cytogenetic analyses were consistent with SNP microarray results. Conclusions: A diagnosis of segmental paternal isoUPD14 was confirmed, consistent with the clinical presentation. SNP microarray fully characterised the molecular abnormality in this case and may be an efficient replacement for traditional microsatellitebased UPD analyses.
Alexandra Jolley1, Lesley McGregor2, Wendy Waters1, Kathie Friend1, Jillian Nicholl1, Sui Yu1,3 1SA Pathology at Women’s and Children’s Hospital, Genetic Medicine, 2SA Pathology at Women’s and Children’s Hospital, South Australian Clinical Genetics Service, 3School of Paediatrics and Reproductive Health, The University of Adelaide, SA, Australia Backgound: Array comparative genome hybridisation (CGH) was requested on a 9-year-old boy with mild developmental delay, mild learning difficulties, short stature and dysmorphic features. Methods: Array CGH used the BlueGnome Cytochip oligo ISCA 8 × 60K platform. Multiplex ligation probe amplification (MLPA) and fluorescence in situ hybridisation (FISH) were also utilised. Results: Array CGH identified a maternally inherited 128 kb interstitial duplication at chromosome Xp21.1 involving exons 10–18 of the DMD gene. FISH indicated that the duplication is located at Xp21. The duplication was confirmed by MLPA and is predicted to cause an in-frame change within the DMD gene. However, his
Print ISSN 0031-3025/Online ISSN 1465-3931 © 2013 Royal College of Pathologists of Australasia
Copyright © Royal College of pathologists of Australasia. Unauthorized reproduction of this article is prohibited.
Genetics
HEPATIC COMPLICATIONS OF ERYTHROPOIETIC PROTOPORPHYRIA Pak Leng Cheong1,3, Bing Yu3, Jole Bojovic1,2, Victor Poulos2, Lucinda Freeman1, Peter M. Stewart2, Ronald J. Trent1,3 Departments of 1Molecular & Clinical Genetics, and 2Clinical Chemistry, Royal Prince Alfred Hospital, Sydney, and 3Sydney Medical School, University of Sydney, NSW, Australia Erythropoietic protoporphyria (EPP) is caused by mutations in ferrochelatase (FECH), the last step in the haem biosynthesis pathway. EPP is inherited in a pseudodominant fashion, most commonly due to presence of a low-expression splicing variant IVS3-48C in trans to a disease causing mutation. Reduction in ferrochelatase activity leads to accumulation of protoporphyrin IX (PPIX) and photosensitivity. Hepatotoxicity is a rare complication of EPP, seen in 1–5% of patients.1 Here we present the first reported case of fatal liver failure secondary to EPP in New South Wales, Australia. The patient was found to carry a known mutation (p.Phe260Leu), but IVS3–48C was not detected. The search for additional modifier genes at the genomic level found several potential candidates. These modifier genes may provide an insight on genotype-phenotype correlations in porphyrias. Reference 1. Anstey AV, Hift RJ. Liver disease in erythropoietic protoporphyria: insights and implications for management. Gut 2007; 56: 1009–18.
creatinine kinase was normal on two separate occasions. Subsequently, a mutation in the SHOC2 gene was identified which is thought to explain this child’s phenotype. Conclusion: The array CGH result is possibly an incidental finding as the SHOC2 gene mutation explains this patient’s symptoms. However, given that this duplication involves an X-linked pathogenic gene, clarification of the clinical significance is required to appropriately manage this patient’s family. Unfortunately, testing of other male family members has not been possible at this time. FISH study is unable to precisely determine if the duplication is within or outside of the DMD gene. This case highlights multiple complex issues in array CGH testing including interpretation of duplications and the importance of correlating the patient’s clinical picture with the array CGH result. Questions for Dr Charles (Buck) Strom 1. What is your approach to determining the pathogenicity of duplications in a diagnostic setting when the clinical picture does not match? 2. Questions for How would you suggest the clinician manage and counsel this family?
SEGMENTAL PATERNAL UPD14 – SNP ARRAY SAVES THE DAY?
Question/discussion point for Dr Charles (Buck) Strom 1. The current state of phenotyping cannot match the high throughput of exome/whole genome sequencing. How do we correlate our findings in the genome to phenotype? 2. In trio exome sequencing where the proband has a sibling, what is our obligation to the sibling in terms of incidental findings?
Chiyan Lau1, Val Hyland1, David Young1, Trent Burgess3, Ralph Oertel3, James Harraway2 1Molecular Genetics Laboratory, Division of Haematology, Pathology Queensland, Royal Brisbane and Women’s Hospital, Brisbane, 2Mater Pathology, Brisbane, Qld, and 3VCGS, Melbourne, Vic, Australia
CHALLENGING ARRAY CGH CASE INVOLVING A DUPLICATION OF EXONS 10–18 OF THE DMD GENE IN A BOY WITH NORMAL CREATININE KINASE LEVELS
Background: A baby in neonatal intensive care with respiratory insufficiency, skeletal dysplasia and dysmorphism was clinically suspected to have paternal uniparental disomy of chromosome 14 (UPD14). Molecular testing for UPD14 was requested. Methods: Microsatellite markers on chromosome 14 were genotyped in the affected child and both parents. Standard karyotype and interphase FISH using probes that map to 14qter were performed on the proband. SNP microarray (Illumina HumanCytoSNP-12) was performed on the parent-child trio. Results: Single nucleotide polymorphism (SNP) microarray detected a copy number neutral segment showing loss of heterozygosity (LOH) of approximately 12 Mb in size at the 14q terminus in the proband, encompassing the UPD14 critical imprinted region at 14q32. A SNP trio analysis showed that this segment was of paternal origin only in the proband, while the remainder of chromosome 14 showed biparental inheritance. The results of microsatellite and cytogenetic analyses were consistent with SNP microarray results. Conclusions: A diagnosis of segmental paternal isoUPD14 was confirmed, consistent with the clinical presentation. SNP microarray fully characterised the molecular abnormality in this case and may be an efficient replacement for traditional microsatellitebased UPD analyses.
Alexandra Jolley1, Lesley McGregor2, Wendy Waters1, Kathie Friend1, Jillian Nicholl1, Sui Yu1,3 1SA Pathology at Women’s and Children’s Hospital, Genetic Medicine, 2SA Pathology at Women’s and Children’s Hospital, South Australian Clinical Genetics Service, 3School of Paediatrics and Reproductive Health, The University of Adelaide, SA, Australia Backgound: Array comparative genome hybridisation (CGH) was requested on a 9-year-old boy with mild developmental delay, mild learning difficulties, short stature and dysmorphic features. Methods: Array CGH used the BlueGnome Cytochip oligo ISCA 8 × 60K platform. Multiplex ligation probe amplification (MLPA) and fluorescence in situ hybridisation (FISH) were also utilised. Results: Array CGH identified a maternally inherited 128 kb interstitial duplication at chromosome Xp21.1 involving exons 10–18 of the DMD gene. FISH indicated that the duplication is located at Xp21. The duplication was confirmed by MLPA and is predicted to cause an in-frame change within the DMD gene. However, his
Print ISSN 0031-3025/Online ISSN 1465-3931 © 2013 Royal College of Pathologists of Australasia
Copyright © Royal College of pathologists of Australasia. Unauthorized reproduction of this article is prohibited.