G.p.283

DNAJB6 was recently identified as a causative gene for limb-girdle muscular dystrophy type 1D (LGMD1D). DNAJB6 belongs to a class of co-chaperones characterized by a J-domain in the N-terminus. To date, six different mutations have been identified in several families from European, North American and Asian countries. The known mutations cause mainly adult onset, slowly progressive proximal muscle weakness, although occasional patients with earlier onset have been reported. The evolution of the disease has been very mild to moderate and respiratory involvement has not been reported. A Finnish family with four affected members, three siblings and their mother, has been studied extensively in the past decade. All patients presented with marked proximal lower limb weakness at the age of 10 to13 years and many reported some weakness from early childhood. Weakness progressed to proximal upper limbs and to some extent also to distal lower limb muscles causing walking difficulties in early adulthood. The mother became wheelchair bound at age 25. Respiratory involvement was a major problem in the family; two sisters had dyspnea in their late teens and their mother died of respiratory failure at age 33. A novel mutation in DNAJB6 was identified in the family as the cause of this very severe, early onset form of LGMD1D. Functional studies of the mutation indicate a more pronounced reduction of the antiaggregation capacity compared to previously known mutations.