Muscular dystrophies: diagnostic approaches in Hungary.

Muscular dystrophies are a genetically heterogeneous group of degenerative muscle disorders. This article focuses on two severe forms of muscular dystrophies and provides genetic data for a large cohort of Hungarian patients diagnosed within the last few years by the authors. The Duchenne/Becker muscular dystrophy (DMD/BMD) is caused by mutations in the dystrophin gene, which is located on chromosome Xp21. The genetic analysis of dystrophin is usually performed by multiplex polymerase chain reaction (PCR), which detects approximately 95% of all deletions but does not distinguish between one and two copies of the exons investigated. The present work, therefore, concentrates on the improvement of the diagnostic panel for the analysis of DMD/BMD in Hungary. Radioactively labelled cDNA probes, encompassing the whole dystrophin gene detect all the deletions and the analysis is quantitative. In addition, the new multiple ligation-dependent probe amplification (MLPA) technique was recently introduced that enabled more reliable and faster quantitative detection of the entire dystrophin gene. The genomic basis of facioscapulohumeral muscular dystrophy (FSHD) is associated with contraction of the D4Z4 repeat region in the subtelomere of chromosome 4q. In case of FSHD, molecular genetic criteria still have to be improved because of the complexity of the disorder.

Congenital myasthenic syndrome (CMS) in three European kinships due to a novel splice mutation (IVS7 - 2 A/G) in the epsilon acetylcholine receptor (AChR) subunit gene.

Mutations in the epsilon-acetylcholine receptor (AChR epsilon) subunit gene cause congenital myasthenic syndromes (CMS) with postsynaptic neural transmission defects. We present 3 male and 2 female patients from three unrelated Croatian, Hungarian, and Russian families with autosomal recessive CMS. All patients manifested with variable degrees of ophthalmoparesis and generalized, fatiguable muscle weakness since birth or early infancy. Electrophysiological studies showed a decremental response in all patients indicating a neuromuscular transmission defect. Pyridostigmine treatment improved the proximal muscle weakness whereas the ophthalmoparesis remained unchanged in all patients. Analysis of the AChR epsilon subunit gene showed homozygosity for a novel splice site mutation of intron 7 epsilon(IVS7-2A/G) in the two Croatian siblings. epsilon-mRNA analysis by RT-PCR and direct sequencing revealed that exon 7 was spliced directly to exon 9 with skipping of exon 8. The Hungarian and Russian patients were heteroallelic carriers of the same mutation epsilon(IVS7-2A/G) and of a frameshifting mutation epsilon 70insG and epsilon 1293insG, respectively. We hypothesize that altered splice products may not be expressed as functional receptors at the cell surface. A haplotype analysis with polymorphic markers revealed a high degree of similarity for the epsilon(IVS7-2A/G) carrying allele in all families and may therefore indicate a common origin of the mutation.

A common mutation (epsilon1267delG) in congenital myasthenic patients of Gypsy ethnic origin.

OBJECTIVE: Mutation analysis of the acetylcholine receptor (AChR) epsilon subunit gene in patients with sporadic or autosomal recessive congenital myasthenic syndromes (CMS). BACKGROUND: The nicotinic AChR of skeletal muscle is a neurotransmitter-gated ion channel that mediates synaptic transmission at the vertebrate neuromuscular junction. Mutations in its gene may cause congenital myasthenic syndromes. A recently described mutation in exon 12 of the AChR epsilon subunit (epsilon1267delG) disrupts the cytoplasmic loop and the fourth transmembrane region (M4) of the AChR epsilon subunit. METHODS: Forty-three CMS patients from 35 nonrelated families were clinically classified as sporadic cases of CMS (group III according to European Neuromuscular Centre consensus) and were analyzed for epsilon1267delG by PCR amplification and sequence analysis. RESULTS: The authors report the complete genomic sequence and organization of the gene coding for the epsilon subunit of the human AChR (accession number AF105999). Homozygous epsilon1267delG was identified in 13 CMS patients from 11 independent families. All epsilon1267delG families were of Gypsy or southeastern European origin. Genotype analysis indicated that they derive from a common ancestor (founder) causing CMS in the southeastern European Gypsy population. Phenotype analysis revealed a uniform pattern of clinical features including bilateral ptosis and mild to moderate fatigable weakness of ocular, facial, bulbar, and limb muscles. CONCLUSIONS: The mutation epsilon1267delG might be frequent in European congenital myasthenic syndrome patients of Gypsy ethnic origin. In general, patients (epsilon1267delG) were characterized by the onset of symptoms in early infancy, the presence of ophthalmoparesis, positive response to anticholinesterase treatment, and the benign natural course of the disease.

Deletion patterns of dystrophin gene in Hungarian patients with Duchenne/Becker muscular dystrophies.

Deletion pattern analysis of the dystrophin gene was performed in 159 Hungarian patients with Duchenne/Becker muscular dystrophy. In 116 cases (73% of total patients), exon deletions were detected by PCR amplification. In 37 patients (31.9% of patients with a deletion) one exon was deleted, while five or more exons were missing in 40 children (34.4%). With respect to the proximal-distal distribution of the deletions, 90 children (77.6%) had deletions exclusively at the 3' end of the gene, 21 deletions (18.1%) affected only the 5' end, and in five patients (4.3%) large-scale deletions were detected, which affected both regions. Analysis of the breakpoint distribution pattern in the dystrophin gene showed that, similarly to that observed in several Western European populations, intron 44 was involved most frequently (n = 35, 15.1%) as a starting breakpoint. In the Hungarian population introns 50 and 52 were the second (n = 30, 12.9%) and third (n = 29, 12.5%) most frequently observed hot spots at the 3' end; these seem to be characteristic for the Hungarian patients. At the 5' end the breakpoint peak (n = 6, 2.58%) was in intron two. As it was proposed by previous national studies, our findings also suggest that certain intronic sequences, characteristic for a population, probably determine the development of a preferential breakpoint profile in this disease.

[Carnitine-deficient cardiomyopathy]. / Karnitinhiányos cardiomyopathia.

The case of a 10 month old girl with carnitine deficiency caused neuromuscular symptoms and cardiomyopathy is reported. After oral carnitine therapy dramatic improvement in neurological status and in cardiac function was confirmed. This case is the first infant our country with dilated cardiomyopathy successfully treated by oral L-carnitine.