Laing distal myopathy pathologically resembling inclusion body myositis

Mutations in MYH7 cause autosomal dominant Laing distal myopathy. We present a family with a previously reported deletion (c.5186_5188delAGA, p.K1729del). Muscle pathology in one family member was characterized by an inflammatory myopathy with rimmed vacuoles, increased MHC Class I expression, and perivascular and endomysial muscle inflammation comprising CD3(+), CD4(+), CD8(+), and CD68(+) inflammatory cells. Interestingly, this biopsy specimen contained TDP-43, p62, and SMI-31-positive protein aggregates typical of inclusion body myositis. These findings should alert physicians to the possibility that patients with MYH7 mutations may have muscle biopsies showing pathologic findings similar to inclusion body myositis.