[Familial myopathy associated with tubular aggregates--report of two siblings]

We reported two siblings with slowly progressive muscle weakness in proximal and peroneal muscles without atrophy, myalgia, cramps, or episodic weakness. The serum creatine kinase level was moderately elevated. The prominent features of their muscle pathology were accumulation of tubular aggregates in type 2 fibers, predominantly in type 2B fibers, and marked type 1 fiber atrophy. Three to eleven % of muscle fibers contained tubular aggregates. Electron microscopic examination revealed accumulation of double-walled tubular structures. Familial myopathy with tubular aggregates as a hallmark of muscle pathology is considered to be a new clinical form of childhood-onset familial myopathies.