Screening for biotinidase deficiency in Austria

SCREENING Screening4 (1995) 71-78

ELSEVIER

Screening for biotinidase deficiency in Austria K. Widhalm*, Ulrike Wintersperger, Sophie Bischof, R. Brix Departments

of Pediatrics

and Oto-Rhinolaryngoscopy.

University

of Vienna,

Vienna,

Austria

Received6 September1994;revision received 10 March 1995;accepted7 April 1995 Abstract Introduction: Biotinidasedeficiencyis an autosomalrecessivemetabolicdisorderthat can produceskin rash, alopecia,seizures,ataxia and developmentaldelay. Early detectionand treatmentwith biotin may prevent thesesymptoms.Newbornscreeningfor this disorderhas beenconductedin many areasof the world. We examinedour resultsin Austria. Methods: 531331newbornsin Austria were screenedfor deficiencyof biotinidaseduring a period of 6 years(1986-91).A calorimetricprocedurewasusedto detect biotinidaseactivity in Iilterpaper blood samplescollectedprimarily to identify PKU and congenitalhypothyroidism. Results: Specimens from 15infantshaddistinctly reducedenzymeactivity. Thus, the incidence of biotinidasedeficiencyin Austria wasestimatedto be approximately 1:35000.In addition, two affected siblings were detected through secondary family screening.Discussion: Biotinidasedeficiencyseemsto be a treatabledisorder.Empiricalevidencesuggests that supplementionof biotin (5-10 mg per day) in affected personscan prevent clinical manifestations. Sincescreeningand treatment are both effective and the incidenceis well within the rangeof other metabolicdisordersfor which neonatal screeningis performed,biotinidase deficiencyis a metabolicdisorderwhich shouldbeincorporatedinto neonatalmass-screening programsfor inborn errors of metabolism.

Keywords: Biotinidasedeficiency;Neonatal screening

1. Introduction Biotinidase deficiency (McKusick 25326) is an autosomal recessive disorder of biotin recycling, characterized by the inability to cleave biotin from biocytin or other biotinylated peptides because of a complete or partial deficiency of the enzyme l Corresponding author,Department of Pediatrics. Universityof Vienna.Wihringer-Giirtel18-20. A-1090Vienna,Austria.Tel.: andFax: +I 404003194.

0925-6164/95/$09.50 0 1995ElsevierScience IrelandLtd. All rightsreserved SSDI 0925-6164(95)00106-V

12

K. Widhalm et al /Screening 4 (1995) 71-78

biotinidase (EC 351.12). Deficient activity of this enzyme is the primary defect in most children with biotin responsive late-onset multiple carboxylase deficiency [I 1. Affected children usually become symptomatic at several months of age and, if untreated, may ultimately develop a variety of cutaneous and neurologic abnormalities, ketosis, seizures, permanent mental impairment, coma and death. These features are presumably caused by deficient activities of one or more of the biotin-dependent enzymes propionyl-CoA carboxylase, pyruvate-CoA carboxylase and @-methylcrotonyl-CoA carboxylase. Biotinidase deficiency meets the following criteria for incorporation into neonatal mass screening programs: (1) Affected children do not show symptoms at birth; (2) the disease may cause permanent neurological abnormalities [2]; (3) the clinical signs could be prevented by biotin therapy; and (4) screening for biotinidase deficiency is inexpensive and has a low recall rate [3,4]. Herein, we report our experience with a national neonatal screening program for biotinidase deficiency in Austria during a &year period. 2. Methods We screen for biotinidase deficiency by punching 3-mm disks from the filter-paper blood specimens (Guthrie cards) sent to the central laboratory for neonatal screening and testing these disks by the semiquantitative biotinidase assay described by Heard et al. [5]. Specimens having initial positive results are re-tested; specifically, another disk is punched from the same filter card and tested. For confirmation of biotinidase deficiency, biotinidase activity is measured in a plasma sample by the method of Knappe et al. [6]. 3. Results During a B-year period (January 1986-December 1991), 531 331 newborns were routinely screened for biotinidase deficiency. A total of 1598 infants (0.3%) had a positive or questionably positive result and, subsequently, a second disk was tested from the same specimen. In 78 of these infants (0.02%) biotinidase activity was markedly reduced or absent. Plasma specimens were obtained from 67 of these 78 infants. Ultimately, the diagnosis of biotinidase deficiency was made on the basis of markedly reduced plasma biotinidase activity in 15 infants [ 1,6]. Each of these infants and the results of family study are listed in Table 1 . All of the infants identified by neonatal screening were clinically well at the time of diagnosis. The finding of 15 affected infants among 531 331 screened newborns yields an incidence of 1:35 422 or approximately 1:35 000 for biotinidase deficiency in the Austrian population. According to the criteria of Wolf and Heard [7] and adopted by others [8], 6 of these infants (4 males) were classified as ‘profoundly deficient’ (c lO%‘of normal enzyme activity) and 9 (7 males) as ‘partially deficient (lo-30% of normal enzyme activity). Additional infants thought to have biotinidase deficiency were found to be only heterozygotes with activity greater than 30%. Biotinidase activity of most of the affected children was tested several times. The

K. Widhalm ei al. /Screening 4 (1995) 71-78

13

enzyme activity in most of them remained unchanged over months or years. Consequently, for these infants only the most recent result is given in the Table 1. A few, however, had an increase in plasma biotinidase activity over time (Table I). In these infants the classification was changed from ‘profound’ to ‘partial’ deficiency. Three (R.P., W.A. and W.L.) regularly received biotin therapy. One patient (W.A.), with residual biotinidase activity of 7.6% of normal, received electrophysiological examinations. Plasma samples taken from this patient at the age of 1.5 months and 5 months showed biotin concentrations within the normal range (1.7 I and 1.43 nmohl). At the age of almost 1 year and 7 months, however, her plasma biotin concentration was found to be subnormal (0.78 nmol/l) and biotin supplementation (5 mg daily) was started, although she was asymptomatic. At the age of 2 years and 9 months this girl had a normal electroencephalogram, normal auditory brainstem-evoked potentials and normal late cortical auditory-evoked responses. In addition, audiometry and magnetic resonance imaging (MRI) of the brain were considered normal. Nevertheless, biotin supplementation was continued. Biotinidase activity was also determined quantitatively in the sera of the parents and siblings of the affected patients. Most of the parents had levels of biotinidase activity that were intermediate between the mean of normal levels and the low levels of affected children. Two affected siblings of one newborn proband (K.A.) were detected through secondary family screening at the age of 14 years and 4 years (K.Z. and K.M.). One (K.M.) was asymptomatic, but his sister (K.Z.) was considered to have reduced intelligence with IQ 82 as determined by the Hamburg-Wechsler-IQ Test (HAWIE) (Table 2). 4. Discussion Austria is one of the few countries in which nationwide screening for biotinidase deficiency is conducted [9]. The incidence in the Austrian population is estimated to be 1:35 000. Recent data from a worldwide screening survey of biotinidase deficiency report an incidence of 1 in 60 089 live births. However, incidences varying from 1:27 000 to 1:277 000 have been reported from various countries [7,9]. The recall rate for false positive results is reported to be from 0.01% to 0.5% [3,4,10]. Thus, recall rate (0.02%) of the Austrian screening program seems to be within the general range. Complete and partial biotinidase deficiency can be distinguished [5,8]. Wolf et al. [9] reported about 142 detected newborns, 76 of whom showed profound deficiency and 66 partial deficiency [8]. In Austria, so far, we have identified 6 profound and 9 partially deficient patients. By means of secondary family screening, we also identified patients with activities of 38.1% and 38.2% of the mean normal activity. These patients have been classified by Dunkel et al. [8] as ‘partial’ deficient, but are probably only simple heterozygotes. We prefer the classification of patients as ‘profound’ (< lo%), ‘partial’ (lo-30%) and ‘heterozygous’ (> 30%). Thus, biotinidase deficiency may be another example of the need for genotypic assignment. It is possible that several different biotinidase alleles exist in the general population, each of which codes for an enzyme with slightly different activity [ 111. The parents of most of the

(m) (born K.M. (f) (born G.P. (m) (born N.M. (m) (born

H.D.

7.6.89)

7.1.90)

9.10.87)

28.8.87)

W.A. (f) (born 3.7.87)

(m) (born 3.4.87)

1 not affected - N.E. (I)

-

-

0.44

1.38

1.19

7.6

23.9

20.6

26

8.3 11.1

1988: 0.48 1990: 0.64

1.50

4.2

0.24

2 affected, one of them retarded - K.Z. (f) and KM. (m) 1 affected - W.L. (I)

K.A.

4.7 13.8

screening

1989: 0.27 1991: 0.80

national

1 not affected - R.T. (f)

R.P. (m) (born 257.86)

in the Austrian % of normal activity

deficiency

Biotinidaseactivity nmol/ml/min

Sibling

Patient

Table 1 Detected cases of biotinidase (1986-1991)

I (27.1)

Acidosis IgM, IgA reduced

Lactate

87: lactate t (25.8) pyruvate t (1.07)

91: acidosis lactate t (43.7) pyruvate f (1.6) ketonuria Lactate t (29.5) pyruvate 1 (1.19)

Clinical or biochemical remarks

program

f: 5.2 m: 3.9 f: 4.36 m: 3.4

f: 4.92 m: 4.23 f: 2.99

f: 3.48 m: 3.24

f: 3.9 m: 3.52

f: 2.47 m: 3.13

Genetics

x

5

Family Poland

left for

2 x 5 mg biotin parents stopped therapy after 2 years Since Feb. 89 1 x 5 mg biotin, since Apr. 90 2 x 5 mg Parents did not cooperate

w

2 x 5 mg biotin, since July 89 1

Therapy

Profound

Partial

Partial

Partial

Profound - partial

Profound

Profound - partial

Type

7 2

L; 3 w 3. 0% Q 2 3 2

s% !-F)

(m)

Mean

normal

21.3.91)

14.3.91)

24.9.90)

(m) (born 16.3.90)

(m) (born 19.1.90)

(born U.D. (f) (born S.R. (m) (born

A.F.

G.D.

H.A.

S.S. (m) (born 8.9.89) G.H. (m) (born 16.9.89) W.L. (f) (born 22.9.89)

biotinidase

activity:

1 not affected. S.B.

2 not affected - H.B. (f), H.A. (m)

1 affected - W.A. (t-)

-

5.78 nmol/ml/min

0.16

0.71

0.89

1.73

1990: 1.46 1991: 2.68

(range:

4.01-7.98);

13.1

12.3

15.4

29.9

25.3 46.4

9.3 16.9

25.4

1.41

1989: 0.54 1990: 0.98

3.6

0.21

lactate:

5.7-22

mg/dl;

Moderate acidosis, lactate: 25.3

Moderate sideropenia organ. Acids in the urine lactate 1 (30.2) pyruvate 1 (1.1) Moderate sideropenia. Lactate t (37.3) pyruvate 1 (1.12) Acidosis lactate t (25) pyruvate t (0.76)

pyruvate:

0.36-0.59

Parents are third-degree cousins f: 0.76 m: 4.91

-

f: 4.11 m: 5.06

f: 3.62 m: 3.35 f: 2.14 m: 3.03 f: 3.48 m: 2.24

mg/dl.

-

-

Partial

Partial

Partial

Partial

Profound - partial

Since apr. 90 2 x 5 mg biotin

-

Partial

Profound

-

1 x 5 mg biotin

2 affected - K.M. (m) and K.A. (m)

2 affected

K.Z. (f) (born 25.2.73)

K.M. (m) (born 9.4.83)

0.25

0.27

Biotinidaseactivity nmol/mVmin

4.3

4.7

% of normal activity

Mean normal biotinidase activity: 5.78 nmoYml/min (range: 4.01-7.98).

- K.Z. (f) and K.A. (m)

Sibling

Patient

Table 2 Affected siblings detected by family screening after proband infant identified

IQ: 82 retarded

Clinical or biochemical remarks

m: 3.52

f: 3.9

m: 3.52 Both parents heterozygote

f: 3.9

Both parents heterozygote

Genetics

2 x 5 mg biotin. Parents stopped therapy after 6 months 2 x 5 mg biotin. Parents stopped therapy after 6 months

Therapy

Profound

Profound

Type

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patients showed biotinidase activities in plasma between those of normal and those of deficient individuals. This is consistent with an autosomal recessive pattern of inheritance. Patients suffering from the profound form (< 10% activity) often show clinical signs at the age of 3 months or soon thereafter. Moreover, Sourmala et al. [12] recently suggested that patients with residual activity below 10% of normal should be treated with biotin, because depletion of free biotin in the brain may occur even earlier than in other tissues and this could be accompanied by discrete neurochemical deviations. It is reported that most severe and life-threatening symptoms of the disorder can be effectively and rapidly resolved by biotin therapy [ 131. Appropriate dosage of biotin (5-10 mg/day) can prevent the appearance of symptoms arising from the block in biotin recycling. Recent reports have stated that children with low residual activity, particularly when stressed by infection, may benefit from prophylactic biotin therapy [ 111. For treatment of patients suffering from partial deticiency, doses of biotin lower than 5-10 mg/day, as used to treat children with profound deficiency, may be sufficient. Taitz et al. [14] described a child with biotinidase deficiency who had severe myopia and progressive retinal epithelial dysplasia and cases of biotinidase deficiency with hearing loss of unknown pathology. Abnormal auditory-evoked potentials could be a indicator to a degenerative process of the central nerve system (CNS). Wolf et al. [ 151, however, described four patients with profound deficiency who had normal auditory evoked responses. So far it remains unclear whether biotin depletion might lead to irreversible hearing loss and visual complications,and to irreversible degenerations in the auditory and visual neuronal systems in the CNS. Therefore, it seems wise to perform auditory and visual testing periodically in all patients with biotinidase deficiency. Further investigations should be conducted to determine whether all neurological features of biotinidase deficiency are reversible or can be prevented by biotin therapy. If early detection and treatment of the disease prevents the occurrence of clinical manifestations, screening programs for biotinidase deficiency should be continued. Consequently, follow-up studies such as those reported from Quebec [5] and Massachusetts [lo] and from Austria, in this report, are important. Acknowledgement We thank Dr. R. Baumgartner, University Children’s Hospital, Metabolic Unit, Basel, Switzerland, for measuring the biotinidase activity levels of our patients and their parents, that are shown in Tables 1 and 2. References [I] Wolf B, Grier RE, Allen RJ, Goodman SI, Cein CL. Biotinidase deficiency:an enzymatic defect in late-onset multiple carboxylase deficiency. Clin Cbim Acta 1983; 131: 273. [2] Wolf B, Heard GS, Jefferson LJ, Proud VK, Nance WE, Weissbecker KA. Clinical findings in four children with biotinidase deficiency detected through a statewide neonatal screening program. N Engl J Med 1985; 313: 16.

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[3] Kennedy K, Girdwood WA, King MD. A pilot study in Scotland. J Inher Metab Dis 1989; 12: 344. [4] Sandner J, Niehaus Ch. Ergebnisse einer Pilotstudie fur ein Neugeborenen-Screening auf angeborenen Biotinidase mangel. Monatsschr Kinderheilkd 1986; 134: 729. [5] Heard GS, MC Voy JS, Wolf B. Screening method for biotinidase deficiency in newborns. Clin Chem 1984; 30: 125. [6] Knappe J, Briimmer W, Brederbick K. Reinigung und Eigenschaften der Biotinidase aus Schweinenieren und Lactobacillus casie. B&hem Z 1963; 338: 599. [7] Wolf B, Heard GS. Screening for biotinidasc-deficiency in newborns: worldwide experience. Pediatrics 1990; 85: 512. (81 Dunkel G, Striver CR, Clow CL, Melancon S, Lemieux B, Grenier A, Laberge C. Prospective ascertainment of complete and partial serum biotinidase-deficiency in the newborn. J Inher Metab Dis 1989; 12: 131. [9) Wolf B. Worldwide survey of neonatal screening for biotinidase deficiency. J Inher Metab Dis 1991; 14: 923. [IO] Lawler MG, Frederick DL, Rodriguez-Anza S, Wolf B, Levy HL. Newborn screening for biotinidase deficiency: pilot study and follow-up of identified cases. Screening 1992; 1: 37. [l l] Seoor MC Voy JR, Levy HL, Lawler M, Schmidt MA, Ebers DD, Hart PS et a!. Partial biotinidasedeficiency: clinical and biochemical features. J Pediatr 1990; 116: 78. [12] Suormala TS, Baumgartner ER, Wick H, Scheibenreiter S, Schweizer S. Comparison of patients with complete and partial biotinidase deficiency: Biochemical studies. J Inher Metab Dis 1990; 13: 76. [13] Ramaekers V Th, Brab M, Rau G, Heimann G. Recovery from neurological deficits following biotin treatment in a biotinidase Km variant. Neuropediatrics 1993; 24: 98. [!4] Taitz LS, Leonhard JV, Bartlette K. Long-term auditory and visual complications of biotinidase deficiency. Early Hum Dev 1985; 11: 325. [15] Wolf B, Grier RE, Allen RJ, Goodmann SI, Kien CL, Parker WD et a!. Phenotypic variation in biotinidase deficiency. J Pediatr 1983; 103: 233.