Myopathy in a patient with systemic AA amyloidosis possibly induced by psoriasis vulgaris: An autopsy case

ABSTRACT Introduction: Amyloid myopathy is a rare manifestation of primary systemic amyloid light‐chain (AL) amyloidosis, but it has not been reported to occur in secondary amyloid A (AA) amyloidosis. Methods: We describe a 46‐year‐old man with psoriasis vulgaris who presented with idiopathic upper and lower limb weakness and was eventually diagnosed with hypertrophic cardiomyopathy. Muscle biopsy findings were compatible with mild inflammatory myopathy. He died of cardiopulmonary arrest, and an autopsy was performed. Results: The autopsy revealed amyloid plaques immunopositive for AA (but not AL or transthyretin) in the perimysial, perivascular, and endomysial regions of the iliopsoas muscle. The final diagnosis was systemic AA amyloidosis with muscle amyloid angiopathy, possibly induced by psoriasis vulgaris. Conclusion: This is an extremely rare autopsy case of myopathy in a patient with systemic AA amyloidosis. The reason for the unusually large amount of amyloid deposition in muscle blood vessel walls remains unclear. Muscle Nerve 52: 1113–1117, 2015