In this study, the results of the first cohort that investigated the molecular and clinical characteristics of Fascio-Scapulo-Humeral Dystrophy-1 (FSHD-1) patients in Turkey will be presented.

A reduced of D4Z4 RU (2-9) was detected in a total of 48 index patients. Then 5 more family members with reduced RU (2-9)and  FSHD phenotype were added to  study. Familial cases comprised 52% of all cases.

Group with low (0-3) CS: The RU was ≥5 (5-9) in 11 patients. The mean age at onset was 27.6±6.9 years, the most prominent initial complaints were asymmetric arm weakness and scapula dislocation (9/11), facial muscle weakness (2/11). All patients exhibited typical FSHD clinic.

Group with medium (4-10) CS: The RU was ≥2 (2-9) in 36 patients. The mean onset age was 17.4±14.3 years. Four patients had tongue weakness/atrophy, 2 patients had deltoid atrophy, and 2 patients had quadriceps muscle weakness with preserved tibialis anterior muscle.

Group with high (11-15) CS:  8 reduced RU were detected in 1 patient (6/53, 11%), remaining 5 patients showed 3-4 reduced RU. The mean onset age was 15.9±13.2 years. One patient had tongue weakness and atrophy.

The correlation between the reduced number of RU and disease severity was similar to the previous reports. Additionally, the distribution of familial and de novo FSHD cases was almost equal in our study, which does not fully overlap with the literature information. In larger cohort studies, the phenotype-genotype correlation in our country will be determined more clearly.