RESUMEN
Background: Facioscapulohumeral muscular dystrophy is the third most common muscular dystrophy with an estimated prevalence of 1 per 20.000 and a normal life expectancy in the majority of patients. However, approximately 15% of patients become wheelchair bound in the course of their life. It is a hereditary autosomal dominant disease with high (95%) penetrance by the age of 20, but with variable degree of phenotypic expression even in the same family group. Symptoms frequently start in the second decade of life, with facial and scapular weakness. Aim: To report the clinical features of seven patients with the disease, seen at a public hospital. Material and Methods: Analysis of seven patients with genetic study seen in a public Hospital in Santiago. Results: The age of patients fluctuated from 18 to 61 years and four were females. The mean age at onset of symptoms was 29 years and four had a family history of the disease. The usual presenting complaint was arm or shoulder asymmetric weakness. Four patients had bone pain. Facial involvement was present in four. A genetic study was done in five patients, the other two patients were relatives, confirming the contraction or lower number of repetitions in D4Z4 region. After 12 years of follow up only 2 patients older than 60 years cannot work and one female patients is in a semi dependent state at the age of 30. Conclusions: The clinical workup in the diagnosis and the timely indication of genetic studies are highlighted, to avoid unnecessary and invasive procedures. The variability in the phenotypic expression in a similar genetic defect is discussed and the genetic or epigenetic mechanisms of this muscular dystrophy are described.