A 40-year-old man presents with muscle weakness. He cannot open his hand for a handshake and cannot extend his arm after flexing it. On physical examination, he has marked atrophy of leg and arm muscles, ptosis, and a fixed facial expression. There is testicular atrophy. Laboratory studies demonstrate mild diabetes. A muscle biopsy reveals atrophy of type I fibers, hyperophy of type II fibers, and numerous fibers with centrally located nuclei. Which of the following is the most likely diagnosis?
Correct Answer: Myotonic dystrophy
Description: Myotonic dystrophy most common form of adult muscular dystrophy, Autosomal dominant disorder Characterized by slowing muscle relaxation (myotonia) and progressive muscle weakness andwasting. Includes hea, smooth muscle, central nervous system, endocrine glands, and eye. Myotonic dystrophy can be separated into two clinical groups: Adult-onset:Atrophy of type I fibres and hyperophy of type II fibres Congenital Unlike the other choices, internally situated nuclei are a constant feature. Necrosis and regeneration, although occasionally present, are not as prominent as they are in Duchenne muscular dystrophy (choice B). Dermatomyositis is a systemic autoimmune disease that typically presents with proximal muscle weakness and skin changes, damage to small blood vessels contributes to muscle injury. Biopsies of muscle and skin may show deposition of the complement membrane attack complex (C5b-9) within capillary beds. Perifascicular atrophy, heliotrope rash and Gottron papules are characteristic. Nemaline myopathy - Childhood weakness; some with more severe weakness, hypotonia at bih ("floppy infant"). Aggregates of spindle-shaped paicles (nemaline rods); occur predominantly in type 1 fibers; derived from Z-band material (a-actinin) and best seen on modified Gomori stain or by electron microscopy.
Category:
Pathology
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