Myopathy with trabecular muscle fibers

A systematic review of muscle biopsies over a 15 year period in a large neu rological hospital revealed 21 cases (7% of the total of noninflammatory my opathies) with a distinctive pattern of myopathology and a limb-girdle clin ical phenotype. The muscle pathology was dominated by a large prevalence (2 0-90%) of trabecular or lobulated fibers in which maldistribution of interm yofibrillar mitochondria produced a lobulated pattern of oxidative enzyme a ctivity on transverse sections. The clinical picture was characterized by a dult onset, slowly progressive muscle weakness affecting mainly proximal li mb musculature, although mild distal weakness was also present in 60% of th e cases. The trabecular pattern of oxidative enzyme reaction reflects maldi stribution of the intermyofibrillar mitochondria; this may be caused by mal function of a putative anchoring mechanism. While trabecular fibers can occ ur as a nonspecific alteration of muscle fibers in many diverse myopathies, the high prevalence of trabecular fibers as the dominant pathology in trab ecular fiber myopathy makes it a distinctive (though not necessarily etiolo gically homogeneous) clinico-pathological entity. (C) 1999 Elsevier Science B.V. All rights reserved.