Distal myopathy secondary to a mutation in myotilin

Dick, D.J., Hammans, S., Xuereb, J.H. and Udd, B. (2008) Distal myopathy secondary to a mutation in myotilin. Journal of Neurology Neurosurgery and Psychiatry, 79 (3), 338.

Abstract

Distal myopathies are inherited primary muscle and may be caused by defects in structural components of the sarcomere. We present a family with a distal myopathy secondary to a mutation in myotilin.
A 70-year-old male reported progressive difficulty walking from his early 50s when he developed a tendency for his feet to flap followed by increasing problems rising from a chair. A younger sister had identical symptoms and their father had an abnormal gait from his fifth decade.
On examination, he had a lordotic gait and a distal pattern of weakness in his lower limbs. Creatine kinase was marginally raised and an MRI of his legs showed a distinctive pattern of fatty replacement of muscle.
Muscle biopsy revealed non-selective fibre atrophy and numerous eosinophilic inclusions surrounded by asophilic granules. Molecular genetic analysis of titan was normal but a myotilin S60C missense mutation was found in both siblings.
Myotilin is a 57 kDa Z-disc component that interacts with alpha-actinin, filamin-C, calsarcin and actin which controls sarcomere assembly. Seven mutations have been reported which give rise to two phenotypes—either LGMD1A or a distal myofibrillar myopathy. This family is only the second to be reported with this particular mutation.

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