Identification of the deletions in the UGT1A1 gene of the patients with Crigler-Najjar syndrome type I from Slovakia

Crigler-Najjar syndrome type I (CN I) is a rare autosomal recessive disorder due to hepatic dysfunction of uridine diphospho-glucuronosyltransferase (UGT) activity toward bilirubin. Complete inactivation of this enzyme causing CN I lead to accumulation of unconjugated bilirubin in serum and bile. Here we report the results of the molecular characterization of the uridine diphospho-glucuronosyltransferase 1A1 (UGT1A1) gene in a consanguineous family of Slovak Roms and an unrelated non-Romany family with CN I. Sequence analysis of UGT1A1 gene in all four Romany patients showed mutation in exon 4, a deletion of an A at codon 407 (1220delA), not yet described in homozygous status. All analysed patients were homozygous for 1220delA mutation and their 3 healthy sibs were heterozygous. The non-Romany patient was a compound heterozygote for two different deletions, 1220delA and 717-718delAG at codon 239. In the family of his cousin a son was born affected with CN I, who was homozygote for 717-718delAG mutation. His other niece affected with CN II was heterozygote for mutation 717-718delAG but homozygote for TA insertion and enhancer substitution T-3279G. Haplotype analysis suggests that the 1220delA mutation is identical by descent in both families, though they originate from two ethnically different populations (Slovaks vs. Roms).

Detection of His1069Gln mutation in Wilson disease by bidirectional PCR amplification of specific alleles (BI-PASA) test

Wilson disease (WD) is an autosomal recessive disorder of hepatic copper metabolism caused by mutations in a gene encoding a copper-transporting P-type ATPase, ATP7B. The majority of known mutations affecting this gene are frequent in different populations, which may help to introduce rapid diagnostic procedures based on direct DNA analysis into routine clinical practise. The His1069Gln mutation in exon 14 is the most frequent one, accounting for 30-60% of all mutations in Caucasian patients. The aim of the present work was to introduce DNA-based direct analysis into routine molecular screening for the above mutation in Slovak WD patients and to assess its frequency in patients as well as in a control population. Twenty seven clinicaly diagnosed patients from twenty five families, twenty relatives of index patients and three hundred and six control DNA samples were tested using two different DNA-based methods: the earlier described amplification created restriction site (ACRS) for Alw21I in combination with nested PCR and the amplification refractory mutation system (ARMS). In 18 of 25 unrelated patients (72%), the mentioned genetic defect was present in at least one copy. In ten of them (40%), the above mutation was detected in homozygous and in eight individuals (32%) in heterozygous state. In seven WD patients (28%), this mutation was not detected. The allele frequency of His1069Gln in Slovak patients with WD was 56%, which was higher as reported in other populations. In a control group of 306 random DNA samples (612 alleles), the His1069Gln mutation was observed in 3 samples (carrier frequency 1%; allele frequency 0.49%). These frequencies correspond to figures observed in different population of European origin. Taken together, we have provided further evidence that the His1069Gln mutation is the prevalent ATP7B mutation in central-european WD patients. Although both methods used in this study worked in our hands reliably, there are in every-day use some drawbacks and limitations inherent to them (PCR reactions in two tubes, possibility of star activity or not complet digestion by restriction endonuclease, etc.). Therefore we developed a simpler, cost effective and rapid DNA diagnostic test based on bidirectional amplification of specific alleles (BI-PASA), which enables detection of homozygotes (wild and mutant) and heterozygotes, respectivelly, in one PCR reaction. The test was highly sensitive and specific, yielding no false-positive or false-negative results. Its reliability and discriminating power was tested on samples of 27 WD patients and 120 random control DNA's, previously genotyped by above mentioned methods. Comparing results of BI-PASA with ACRS and ARMS tests showed 100% concordance.

High frequency of GJB2 mutation W24X among Slovak Romany (Gypsy) patients with non-syndromic hearing loss (NSHL)

Mutations in the GJB2 gene (connexin 26) represent a major cause of autosomal recessive non-syndromic hearing loss (NSHL) worldwide. In most Caucasian populations, the 35delG mutation in this gene was found to account for up to 50% of cases of the genetic non-syndromic childhood deafness. In populations of non-European ethnic background, other GJB2 gene mutations are occasionally common, e.g. 167delT in Ashkenazi Jews, R143W in Africaans and 235delC in Koreans. In this work, DNA samples from 54 unrelated NSHL patients from endogamous and inbred population of Slovak Roms (Gypsies) from Eastern Slovakia were screened for GJB2 mutations. The coding region of the GJB2 gene of patients was sequenced and mutations W24X, R127H, V153I, L90P and V37I were found. In Slovak Romany population, mutation W24X accounts for 23.2%, R127H for 19.4%, 35delG for 8.3%, V153I for 3.7%, L90P for 3.7% and V37I for 0.9% of screened chromosomes. As the W24X mutation was previously found in India and Pakistan, were from the European Romanies originate, it was brought by the European Romnanies from their Indian homeland. The carrier frequency of 35delG was estimated for Slovak non-Romany population to be 3.3%, and for Slovak Romany population to 0.88%. The carrier frequency of W24X varied in different Slovak Romany subpopulations from 0.0% up to 26.1%.

Identification of three novel SEDL mutations, including mutation in the rare, non-canonical splice site of exon 4

Spondyloepiphyseal dysplasia tarda (SEDT) is an X-linked recessive disorder, characterized by disproportionately short stature and degenerative joint disease, which manifests in the early teens. The gene responsible for SED tarda, SEDL, has been identified in Xp22. We report on three novel SEDL mutations. The first mutation is in the rare, non-canonical 5' splice site of intron 4 (IVS4+4T>C) in an Italian family. Reverse transcription-polymerase chain reaction (RT-PCR) analysis has revealed that this mutation causes alternative splicing of exon 5, and, as a consequence, inclusion of exon 4b sequence. This gives rise to an altered, truncated SEDL protein. We also describe two new deletions: one is a 4-bp deletion in exon 6 [333-336del(GAAT)], identified in a Slovak patient with SEDT, and one is a 1.335-kb deletion (in5/ex6del), found in a Belgian patient. The identification of these novel mutations in SEDL adds to the spectrum of 30 mutations previously identified. A short summary of all currently known SEDL gene mutations is presented.

High frequency of alkaptonuria in Slovakia: evidence for the appearance of multiple mutations in HGO involving different mutational hot spots

Alkaptonuria (AKU) is an autosomal recessive disorder caused by the deficiency of homogentisate 1,2 dioxygenase (HGO) activity. AKU shows a very low prevalence (1:100,000-250,000) in most ethnic groups. One notable exception is in Slovakia, where the incidence of AKU rises to 1:19,000. This high incidence is difficult to explain by a classical founder effect, because as many as 10 different AKU mutations have been identified in this relatively small country. We have determined the allelic associations of 11 HGO intragenic polymorphisms for 44 AKU chromosomes from 20 Slovak pedigrees. These data were compared to the HGO haplotype data available in our laboratory for >80 AKU chromosomes from different European and non-European countries. The results show that common European AKU chromosomes have had only a marginal contribution to the Slovak AKU gene pool. Six of the ten Slovak AKU mutations, including the prevalent G152fs, G161R, G270R, and P370fs mutations, most likely originated in Slovakia. Data available for 17 Slovak AKU pedigrees indicate that most of the AKU chromosomes have their origins in a single very small region in the Carpathian mountains, in the northwestern part of the country. Since all six Slovak AKU mutations are associated with HGO mutational hot spots, we suggest that an increased mutation rate at the HGO gene is responsible for the clustering of AKU mutations in such a small geographical region.

[Cytoprotective effect of Amifostine in the combined chemotherapy of advanced ovarian carcinoma]

The authors treated 10 patients with advanced (stage III-IV) ovarian cancer with a high-dose cyclophosphamide and cisplatin (CP) combined therapy in amifostine protection. Due to the effect of the cytoprotective agent the cycles of treatment were well tolerated and 7 of 10 patients achieved a complete remission. Nephrotoxicity, allergic reaction or minor complications did not occur. Starting of the next treatment cycle was to be delayed in only one case because of anaemia. The agent has an implicit place in the treatment of patients with ovarian cancer in order to achieve better results and improve the quality of life.

Analysis of the SMN and NAIP genes in slovak spinal muscular atrophy patients

We identified homozygous absence of exon 7 of the telomeric copy of the survival motor neuron gene (telSMN) in 88.4% (38/43) of spinal muscular atrophy (SMA) patients from Slovakia. Additional deletions within the neuronal apoptosis inhibitory protein (NAIP) gene were found in 38.5% of type I, 12.5% of type II and never in type III SMA patients. Neither the SMN nor the NAIP gene was deleted in 81 healthy relatives and 25 controls tested. In one family, pseudodominant inheritance was identified. Both the type III SMA father and type II SMA son carried the homozygous deletion of the telSMN gene. One SMA I patient showed an SMN hybrid gene, probably created by intrachromosomal deletion. In two haploidentical type II SMA sibs, the telSMN exon 7 was absent on one chromosome, while the other carried an A-->G transition 96 bp upstream of exon 7 of the telSMN gene, a potential disease-causing mutation in these patients.

Identification of a single ancestral CYP1B1 mutation in Slovak Gypsies (Roms) affected with primary congenital glaucoma

Primary congenital glaucoma (PCG) is an autosomal recessive eye disease that occurs at an unusually high frequency in the ethnic isolate of Roms (Gypsies) in Slovakia. Recently, we linked the disease in this population to the GLC3A locus on 2p21. At this locus, mutations in the cytochrome P4501B1 (CYP1B1) gene have been identified as a molecular basis for this condition. Here, we report the results of CYP1B1 mutation screening of 43 PCG patients from 26 Slovak Rom families. A homozygous G-->A transition at nucleotide 1505 in the highly conserved region of exon 3 was detected in all families. This mutation results in the E387K substitution, which affects the conserved K helix region of the cytochrome P450 molecule. Determination of the CYP1B1 polymorphic background showed a common DNA haplotype in all patients, thus indicating that the E387K mutation in Roms has originated from a single ancestral mutational event. The Slovak Roms represent the first population in which PCG is found to result from a single mutation in the CYP1B1 gene, so that a founder effect is the most plausible explanation of its increased incidence. An ARMS-PCR assay has been developed for fast detection of this mutation, thus allowing direct DNA based prenatal diagnosis as well as gene carrier detection in this particular population. Screening of 158 healthy Roms identified 17 (10.8%) mutation carriers, indicating that the frequency of PCG in this population may be even higher than originally estimated.

[Analysis of inversion in intron 22 of the factor F VIII:C gene in patients with hemophilia A in the Slovak population]

Hemophilia A is the result of Factor F VIIIC (F8C) gene mutations. Predominating mutation is inversion, occurring in about 50% of patients with severe form of the disease. Inversion is the result of homologous recombination between gene A located on the 22. introne of the F8C gene and one of its telomeric copies located about 500 kb from 5'end of the factor F VIIIC gene. This study presents the results of this mutation screening in 84 nonrelated patients with hemophilia A. Inversion was identified in 22 (50%) of 44 patients with severe form and in 1 (from 13) with moderate form of the disease. Distal type of inversion was more frequent (82.6%) than proximal one. The identification of iversions enabled direct DNA diagnosis in 50% of patients with severe form of the disease and will be successfully used in the prenatal diagnosis and carrier testing, mainly in families with sporadic occurrence of the disease. (Tab. 1, Fig. 2, Ref. 18.)

Factor VIII gene inversions in haemophilia A patients of Slovakia

Haemophilia A is caused by a broad range of mutations in the factor VIII (FVIII) gene. The most frequent of them is a large inversion, which appears to be the underlying defect in approximately 45% of all severely affected patients (FVIII < or = 1%). The results here are of 84 unrelated Slovak haemophilia A cases. The factor VIII inversion was identified in 22 of 44 (50%) patients with severe haemophilia A and in 1 of 13 patients with moderately severe disease. The inversions of distal type were more frequent (82.6%) than proximal ones (17.4%).

[The spectrum of mutations in the CFTR gene in patients with cystic fibrosis in Slovakia]

Up to present, more than 500 mutations have been described in the CFTR gene of patients affected by cystic fibrosis (CF). The vast majority of them, however, are extremely rare, and in fact, were detected only in the original reported cases. This study is aimed at analysis of 9 known mutations in the CFTR gene in CF patients within the population of Slovakia. The region in question of the human genome was analysed by means of polymerase chain reaction (PCR), digestion with the appropriate restriction enzyme, followed by electrophoretic separation of generated DNA fragments. 7 different mutations were identified on 234 CF-chromosomes, which made up 74.36% of all CF-mutations: delta F508--59.4%, G542X--5.56%, R553X--3.42%, N1303K--2.99%, R347P--1.71%, W1282X--0.85%, and 3849 + 10kb--0.43%. In 57.26% of patients mutations were identified on both homological chromosomes, in 33.33% on one of them, and only in 9.4% of patients there were none of the analysed mutations found. These results provide a good basis for the planning and setting up of an effective strategy for direct DNA-based diagnosis of CF in Slovakia. (Tab. 4, Ref. 19.)

Linkage of autosomal recessive primary congenital glaucoma to the GLC3A locus in Roms (Gypsies) from Slovakia

The autosomal recessive form of primary congenital glaucoma (gene symbol GLC3) has been recently mapped to two different loci, GLC3A (at 2p21), and GLC3B (at 1p36), respectively, on families of Turkish and Saudi Arabian provenance. This disorder is known to occur with an extremely high incidence in Roms (Gypsies) in Slovakia. We performed a standard linkage analysis on a sample of 7 Slovak Gypsy families comprising 18 affected members, and found significant linkage with four STR markers from the chromosomal region of 2p21 (D2S1788, D2S1346, D2S2328, and D2S1356), without heterogeneity. This finding demonstrates that in the Rom population of Slovakia, primary congenital glaucoma is due to the locus GLC3A, and consequently, to the mutation(s) in the cytochrome P4501B1 gene, which has been recently identified as the principal cause of the disease. Roms represent the third population, in which the disorder has been mapped to GLC3A.

Distribution of 9 common mutations in the CFTR gene in Slovak cystic fibrosis patients

The distribution of 9 known mutations in the CFTR gene were studied in 234 CF chromosomes originating from 117 unrelated cystic fibrosis (CF) patients from Slovakia, a population which is geographically situated at the borders between Western and Eastern Europe, and Northern and Southern Europe. The following 7 mutations were identified in this sample: delta F508 (59.4%), G542X (5.56%), R553X (3.42%), N1303K (2.99%), R347P (1.71%), W1282X (0.85%), and 3849 + 10 kb (0.43%). These mutations represent 74.36% of all CF mutations, providing a good basis for direct DNA-based diagnosis of CF in Slovakia.

A new extremely large allele at the D1S80 (MCT118) locus

A new extremely large allele at locus D1S80, segregating in a three-generation family is described. The length of PCR-generated allele is approximately 1000 bp. Restriction analysis indicates that this increase is due to an increased number of basic core sequence. The assessed number of tandem repeats is in range 52-55, corresponding to 979-1027 bp exact length of the PCR-generated fragment.

PKU in Slovakia: mutation screening and haplotype analysis

The restriction fragment length polymorphism haplotypes and seven common mutations in the phenylalanine hydroxylase gene were analysed in 49 unrelated Slovak phenylketonuria (PKU) families of Caucasian origin. The predominant mutation in this population sample is R408W, with a frequency of 45.9%. In addition, four other mutations have been identified at relatively high frequencies: IVS12nt1, 10.2%; R158Q, 7.1%; R261Q, 7.1%; R252W, 2.0%. The mutation-haplotype associations correspond to those described in other European populations. The high proportion of mutations (72.4%) amenable to simple rapid detection based on the polymerase chain reaction provides a good basis for direct DNA-diagnosis of PKU in the Slovak population.

Distribution of ApoBII, MCT118 (D1S80), YNZ22 (D17S30), and COL2A1 Amp-FLPs (amplified fragment length polymorphisms) in Caucasoid population of Slovakia

Amp-FLPs are simple and rapid tools for genetic characterization of both individuals and populations. This paper presents allele frequencies of four Amp-FLPs (ApoBII, MCT118, YNZ22, and COL2A1) based on the analysis of more than 100 unrelated Caucasoid Slovaks. The proportion of heterozygotes observed and expected, and the probability that two individuals taken at random from the population would be identical in a given polymorphism (PI), was determined for each Amp-FLP.

[DNA analysis in classic phenylketonuria--screening for mutations and haplotype analysis in Slovak families]

Authors in this contribution present the results of screening for mutations in PAH gene responsible for classical phenylketonuria (PKU), and that of haplotype analysis, based on DNA analysis in 49 Caucasian families with at least one affected child from Slovak Republic. The clearly predominant PKU mutation in this population was the R408W with proportion of 45.9% among all PKU mutations. In addition four other mutations have been identified: IVS12nt1-10.2%, R158Q-7.1%, R261Q-7.1%, and R252W-2.0%. the overall proportion of identified PKU mutations equals 72.4%. Considering the fact, that these mutations are amenable to rapid and rather simple detection using PCR, the DNA analysis is recommended as a method of direct diagnosis in clinical practice as well as in prevention.

[Molecular genetic analysis of deletions in the Duchenne and Becker types of progressive muscular dystrophy]

Methods of molecular genetics (Southern's hybridization and DNA amplification by the PCR method) were used to search the DNA of patients suffering from the Duchenne (DMD) and the Becker (BMD) type of progressive muscular dystrophy for deletions in the dystrophin gene. The series consisted of 29 patients with DMD and 2 patients with BMD. As hybridization probes cloned cDNA sections were used designated as CF56a, CF56b, 1-2a, 2b-3, 4-5a, 5b-7 and 8. With the PCR methods means for exons 8, 19, 45 and 48 were used. No deletion was found in either of the BMD patients. In 13 (44.8%) of the 29 DMD patients deletion with at least one cDNA probe was found. Most deletions were detected with the probes 8 (46.2%) and 1-2a (30.8%). The high proportion of deletions in the etiology of DMD/BMD has both a high differential diagnostic value and allows to make direct prenatal diagnosis as well as to determine transmission in these families with subsequent elimination of the risk of diagnostic error resulting from recombination in DNA diagnosis by means of binding. (Tab. 1, Fig. 2, Ref. 20.)

[Identification of a de novo mutation in a factor FVIII:C gene in a family requesting prenatal diagnosis of hemophilia A]

Hemophilia is caused by wide spectrum of different mutations in the F8C gene which made the direct DNA diagnosis of the diseases not the case of choice. Indirect DNA diagnosis by means of linked restriction fragment length polymorphisms (RFLPs) provides the alternative. Using this method authors identified de novo mutation in a family requiring prenatal diagnosis of hemophilia A. This de novo mutation arose during the spermatogenesis of the proband's father. Attempts to characterize the mutation on the molecular level are presented. (Ref. 15, Fig. 1.).

Deletion delta F508 and haplotype analysis of CFTR gene region in Slovak CF patients

Analysis of a sample of 50 unrelated cystic fibrosis (CF) patients and 46 nuclear families from Slovakia (Czechoslovakia) by the polymerase chain reaction and Southern hybridization revealed that the proportion of the delta F508 mutation was 58% in this population, and that the frequency of the B (i.e., KM19/XV2c [1-2]) haplotype was increased in both delta F508 and non-delta F508 CF chromosomes (98% and 46%, respectively). These results support the view that the trans-European gradient of the delta F508 frequency is of a geographical rather than of an ethnic origin, and that in Slavonic populations, there exists an as yet unidentified but frequent CF mutation other than delta F508, associated with the B haplotype.

[The delta F508 mutation which causes cystic fibrosis and its association with closely linked DNA polymorphisms in the Slovak population]

Linkage relationships between DNA polymorphism metH/TaqI as well as KM19/PstI and the mutation causing cystic fibrosis (CF) were analyzed in 48 families from Slovakia with th occurrence of CF. The polymorphism metH/TaqI did not show linkage disequilibrium with CF mutation. A pronounced allelic association was however found between CF mutation and KM19/PstI polymorphism. Of the 83 CF chromosomes analyzed, the given mutation was associated with the 6.6 kb allele in 82% of cases, while the rate of this allele in chromosomes without the mutation amounts only to 24%. The value of the standardized disequilibrium coefficient SCD = 0.58. Delta F508 deletion was addressly studied in 25 patients (i.e. 50 CF chromosomes). Of the 50 CF mutations, the given deletion was in 64% (32), while the remaining 36% (18) of mutations were of other, closely not identified types. Delta F508 deletion is in marked allelic association with the 6.6 kb allele of KM19/PstI polymorphism (SCD = 0.68). Between the given allele of KM19/PstI polymorphism and CF mutation no other allelic association was found but with delta F508. (Tab. 6, Fig. 1, Ref. 18).

Frequency and distribution of deletions in dystrophin gene in Duchenne muscular dystrophy patients from an east-European Slavonic population

In 32 unrelated DMD patients originating from Slovakia (Czechoslovakia), screening for deletions in the dystrophin gene was performed with cDNA probes Cf56a, Cf56b, 1-2a, 2b-3 4-5a, 5b-7, and 8. In 14 out of 32 DMD patients (43.75 per cent), a deletion extending from one to three adjacent probes was observed. The highest proportion of deletions was found with probes 8 and 1-2a (50 and 28.6 per cent of all deletions, respectively). All these proportions are similar to those found in other populations of European origin.

[Use of DNA analysis in the diagnosis and prevention of hemophilia A]

Hemophilia A belongs to the monogenically determined diseases. The methods of molecular genetics (recombinant DNA) have greatly contributed both to the elucidation of the genetic basis of these diseases and to the elaboration of effective preventive approaches either by prenatal genetic diagnosis or by detection of heterozygous transmitters. The authors present a short survey of the results in the field of genetic research of hemophilia A at molecular level achieved over the last years and they report on their own results of DNA analysis in 15 families with the occurrence of the disease. Of 17 potential subjects transmission was excluded in 10 and confirmed in 7 cases. The importance of early and complete detection of families with the occurrence of hemophilia A is emphasized particularly in the light of effective prevention.

[The yield and quality of DNA extracted from blood samples stored under various conditions]

The effect of different conditions of blood sample storage on the yield and quality of the extracted DNA was studied. Samples of whole umbilical blood were divided into eight groups containing 10 samples each and stored as follows: A--no storage, DNA extracted immediately; B--24 hours at 4 degrees C; C--24 hours at room temperature; D--7 days at 4 degrees C; E--3 months at -18 degrees C; F--6 months at -70 degrees C; G--14 days at -70 degrees C, the samples were thawed one time and frozen again; H--14 days at -70 degrees C, the samples were 3 times thawed and frozen. DNA was isolated and yields quantified by spectrophotometry at 260 and 280 nm. The average DNA yield in the individual groups ranged from 574.5 to 1,075 micrograms per 10 ml of whole blood. Although variations in the yield of DNA were observed both within and among groups, there were no significant changes with respect to different storage conditions. However group H yielded significantly more DNA (900 micrograms/10 ml, p less than 0.05) compared to the control group A. After digestion with restriction endonuclease and electrophoresis in agarose gel, all DNA preparations were found to be of high molecular weight and in digestible condition. The results can be used to advantage in storing DNA for purposes of molecular diagnosis of genetic diseases.

[Genetic linkage of the autosomal dominant form of Charcot-Marie-Tooth amyotrophy and 3 genetic markers on chromosome 1]

In a large pedigree with the autosomal dominant form of Charcot-Marie-Tooth neuropathy type I (CMT 1) segregating in four generations, genetic linkage was studied between this disease and three genetic markers from the centromere region of chromosome 1: Duffy blood group (Fy), salivary and pancreatic isoamylases (AMY 1, AMY 2), and DNA polymorphism at the antithrombin III locus, detected with the probe pAT3c. The lod-scores found do not support linkage between CMT 1 and both Fy and AT 3, since they are negative for all recombination frequencies. Very close linkage could have been excluded. For the AMY polymorphism, the pedigree was not linkage-informative. In agreement with the data from literature, these results support the notion of genetic heterogeneity of CMT 1: in the pedigree under study, the responsible locus is probably not in the centromeric region of the chromosome 1, where it was shown to map to in several other pedigrees. Thus, there seem to exist at least two loci responsible for this type of CMT disease.

Estimating the error rate in DNA diagnosis with linked markers

Recombination between the marker locus and disease locus introduces a risk of diagnostic error that must be considered when performing indirect diagnosis of monogenic disorders by means of a linked DNA polymorphism or another marker. A method is presented which improves the hitherto used estimates of the magnitude of this error. Principally, it makes use of the fact that recombination between marker and disease locus needs not necessarily increase the error rate; if it occurs twice or several times during the diagnostic process, the final diagnosis may be correct.

Notes on the genetics of congenital glaucoma

Relying on the analysis of 81 non-Gypsy families with congenital glaucoma from the entire territory of Slovakia, the authors discuss the share of the genetic component in the etiology of the disease. The characteristics of the families of this series resembled those of comparable series as far as the percentage of familial occurrence, the percentage of bilateral occurrence (73.56%), the percentage of parental consanguinity (4.87%) and in the prevalence of males with a ratio of 1.55:1 are concerned. The incidence of the disease in Slovakia varies around 1 per 22,000 live-born infants. In the non-Gypsy population of Slovakia, the authors assume a multifactorial etiology.