Myopathy Associateci with Amyloid Angiopathy

Abstract

SummaryA 38-year-old patient with the clinical picture of a progressive myopathy resembling limb girdle muscular dystrophy is presented. Muscle biopsy showed amyloid deposits in the walls of small endomysial blood vessels. There was no clinical or physiological evidence of peripheral nerve involvement, no plasma cell dyscrasia and no generalized amyloidosis. There was no muscle fiber hypertrophy, inflammation or neurogenic change. There was no response to steroid therapy.The etiopathogenesis of this amyloid angiopathy is undetermined. The extensive vessel involvement with amyloid deposition and the absence of changes indicative of muscular dystrophy or inflammatory myopathy leads us to favor an ischemic basis for this patient’s myopathy.

Electrophysiologic findings in amyloid myopathy

“…1,2,4,8,[11][12][13] In these cases, fibrillation potentials and short-duration, lowamplitude, polyphasic MUPs either were present diffusely or appeared to be more prominent in proximal muscles. 1,4,11,12,13,19 Nerve conduction studies were usually normal, although two patients had mildly slowed conduction velocities.…”

“…5 Patients with amyloid myopathy typically present with proximal more than distal weakness, dysphagia, macroglossia, and muscle pseudohypertrophy. 2,6,[8][9][10][11]13 Isolated respiratory failure as a presenting manifestation has also been reported. 1,14,16 Muscle biopsy remains the mainstay of diagnosis and typically reveals amyloid infiltration surrounding muscle fibers and vessels.…”

Cerebral amyloid angiopathy. A critical review.

“…8889 A myopathic syndrome with amyloid involvement of the muscle microvasculature, microscopically quite similar to CAA in individual vessels, has been described. 90 Visceral ischemia has been shown to result in very rare instances from a similar sort of systemic microvascular amyloid deposition." Systemic amyloid may produce other types of "remote" effects on the central nervous system (CNS).…”

Primary amyloidosis presenting as “dropped head syndrome”

“…Other histological changes include denervation atrophy, degenerating fibers, and mild perivascular,11, 23 perimysial, or endomysial inflammation, sometimes with an erroneous diagnosis of polymyositis 27. The mechanism by which amyloid deposits cause muscle weakness has not been determined, but theories include ischemic myopathy in cases with predominant perivascular amyloid distribution,36, 37 and mechanical38 or electrical conduction dysfunction in cases with interstitial deposition 39…”