Calpain 3 deficiency presenting as fibre type disproportion: Scientific correspondence

Congenital fibre type disproportion (CFTD) is a histological abnormality characterized by small type 1 muscle fibres, normally sized type 2 fibres and absence of other pathological features [1]. Type 1 fibre hypotrophy is observed in various neuromuscular disorders; thus CFTD should refer only to cases of fibre type disproportion (FTD) having the clinical features of a congenital myopathy and when other neuromuscular conditions have been ruled out [1]. A 36 year-old man, the only son of non consanguineous parents, had a normal birth and early development. Family history was unremarkable. At age 4 he presented with difficulty in climbing stairs and serum creatine kinase (CK) was twice the normal value. On clinical examination proximal limb and spine flexor muscles were weak whereas facial and neck muscles were spared. Shortening of the Achilles tendon was observed. A biopsy of the left vastus lateralis muscle showed FTD.