[Genetic investigations in facioscapulohumeral muscular dystrophy: a preliminary report]

Facioscapulohumeral muscular dystrophy (FSHD) is a primary muscle disorder with autosomal dominant inheritance. FSHD was mapped to chromosome 4 locus q35, but the gene is not yet known. It is characterised by progressive, often asymmetric, selective muscular weakness and great clinical variability. The aim of the study was to analyze 62 FSHD cases from 44 Polish families in which the diagnosis was confirmed by DNA analyses. FSHD diagnosis was based on the clinical findings and standardized investigations confirming primary muscular involvement (EMG, muscle biopsy). DNA analysis was based on EcoRI/BlnI restriction enzyme digestion followed by hybridization with P13E-11 molecular probe. In our material, we have found a relatively large percentage (41%) of big deletions (EcoRI/BlnI fragment of 10-15 kb [kilo bases]), which in the majority of cases (67%) was present in isolated cases. In 10 families (23%) the phenotype was assessed as severe. These are cases with the onset before the age of 10 and fast progression. "Middle sized" deletions (EcoRI/BlnI fragment of 16-29 kb) were prevalent in familial cases and present in 57% of families. "Small" deletion was found in one family (EcoRI/BlnI fragment of 30 kb). Somatic mosaicism was confirmed in one case. De novo mutations were shown in 11% of the examined families. The results of this study indicate that the bigger the deletion, the more severe the FSHD course, however there are some exceptions. A similar relationship has been shown by previous research. Molecular analyses are particularly important in atypical and sporadic cases. It is the first genetic presentation of a group of patients' with this kind of dystrophy in the Polish population.