Amyloid myopathy: Characteristic features of a still underdiagnosed disease

Abstract

A 62-year-old man with progressive proximal weakness underwent extensive evaluation including muscle biopsy without a clear diagnosis being established. A repeat muscle biopsy including Congo red-stained sections revealed infiltration of blood-vessel walls and endomysium with amyloid protein, as well as an unusual pattern of pathologic changes to muscle fibers. From a review of 79 cases of amyloid myopathy reported in the English-language literature, the characteristic features of this disorder are described. Congo red-stained sections of muscle biopsy viewed under fluorescent or polarized optics, and serum or urine protein immunoelectrophoresis, play an important role in the evaluation of myopathy. Amyloid myopathy should be a consideration in adults with progressive neuromuscular weakness of uncertain cause.

Axial myopathy due to primary amyloidosis

“…3,4 A small proportion of the patients (10%) had distal predominant weakness. 3 A case of amyloid myopathy presenting with distal weakness and atrophy of finger flexors has been described previously. 13 The second series 11 looking at the clinicopathological features of 16 patients with confirmed amyloid myopathy found that there was a frequent association with plasma cell dyscrasias.…”

“…Two series 3,11 reviewing the clinical and presenting features of patients with muscle weakness and biopsy evidence of amyloid deposition within skeletal muscle have been published. The larger of the two studies 3 reviewed 79 patients and found that proximal muscle weakness was the most common finding, present in 90% of the patients.…”

“…Other frequent manifestations included fatigue, autonomic symptoms, weight loss / decrease in appetite, and macroglossia or muscle pseudohypertrophy. 3,11 An atrophic form of amyloid myopathy exists whereby patients present with muscle weakness and atrophy without pseudohypertrophy and macroglossia. 3,4 A small proportion of the patients (10%) had distal predominant weakness.…”

“…3,11 An atrophic form of amyloid myopathy exists whereby patients present with muscle weakness and atrophy without pseudohypertrophy and macroglossia. 3,4 A small proportion of the patients (10%) had distal predominant weakness. 3 A case of amyloid myopathy presenting with distal weakness and atrophy of finger flexors has been described previously.…”

Muscle Hypertrophy in a Patient with Immunoglobulin D Multiple Myeloma

“…5 Unlike these diseases, serum CK is often normal in patients with amyloidosis. 6 It is important to consider amyloidosis, in particular when serum CK is not elevated, for the patients whose muscles are hypertrophic without exercise.…”