Facioscapulohumeral muscular dystrophy is a unique muscle disease in that it affects muscles of face and shoulder girdle and is slowly progressive. Here is a brief account of this muscle disease.
It is an autosomal dominant genetic disorder, which is tandem repeat deletion at 4q35 gene. Disease will be severe with increased deletion, hence longer the deletion severe the disease. "Anticipation" is the phenomenon that describes the expected worsening in the subsequent generations because deletion increases in length in every next generation.
Its prevalence is 10 to 20 per one million. Its penetrance varies between the genders, being 95% in males and 65% in females.
Symptoms start during adolescence or early adulthood and usually are slowly progressive.
Predominant weakness over face is that of orbicularis oculi, orbicularis oris and zygomaticus. This pattern of weakness causes difficulty in eye closure and expressionless face. Expressionless face results from the fact that there is enormous difficulty in burrying the eyelashes, pursing the lips, sipping from a straw and whistling. As disease progresses distal muscles also get affected such as biceps brachii, triceps brachii, hip girdle muscles and even forearm muscles & ankle dorsiflexors.
Shoulder girdle symptoms include lateral displacement and medial border winging of scapulae. It is different from other muscular dystrophies in that there is asymmetry in muscular involvement. These symptoms result from weakness of serratus anterior, rhomboids, trapezii, shoulder abductors and shoulder external rotators. Fair amount of power can be demonstrated in deltoids after stabilization of shoulder girdle. As disease progresses weakness spreads distally affecting biceps brachii, triceps brachii, hip girdle muscles and even forearm muscles & ankle dorsiflexors.
Coat's Syndrome is a variant of facioscapulohumeral muscular dystrophy with early onset and rapid progression. It starts early in the childhood and patient becomes wheel chair bound by late second or early third decade. It is also associated with sensorineural hearing loss and progressive exudative telangiectasia of the retina, which must be identified very early during its course to prevent blindness.
Patients presenting with facioscapulohumeral muscular dystrophy may already have entered into early stage of its complications. As disease progresses, despite being very slow in progression, it leads to development of contractures, spinal deformity in the form of hyperlordosis & scoliosis, mild restrictive lung disease and rarely cardiac conduction defects.