A 6 year old boy presents with progressive weakness in muscles, and difficulty in walking upstairs. He has difficulty in walking on his toes and has a waddling gait. Hypertrophy of calf muscles in noted. His CPK is the most appropriate diagnosis–levels are 10,000 LU. Which of the following is most appropriate diagnosis –
Clinical features of liV D 
The age of onset is 2-5 years.
Early development of the child is normal, the disease begins to manifest when the child statrts walking.
The child walks clumsily, has difficulty in climbing stairs and the gait is waddling.
Hypertrophy of calf muscle is a characteristic sign and is visible by the age of 4-5 years.
This is called pseudohypertrophy because it is not true hypertrophy of muscles, instead the muscle is replaced by fat and connective tissues.
Pelvic girdle involvement is very common and can be elicited by Gower's sign:
There is characteristic involvement of the muscle
Duchenne muscular dystrophy
Polymyositis
Congenital myopathy
Myotonia congenita