Cap myopathy

Cap myopathy is a rare congenital myopathy morphologically characterized by the presence of cap-like structures which are sharply demarcated structures of disorganized thin filaments in the periphery of muscle fibers. These structures are in fact disarranged myofibrils with enlarged Z discs and no thick filaments. The severity of the disease is related to the number of fibers affected. Therefore, patients may present with a neonatal fatal form or have a more stable course of the disease in the infant non-fatal form. Respiratory problems are common. All the currently recognized genes associated with cap myopathy (TPM2, TPM3 and now ACTA1) encode components of the sarcomeric thin filaments.