Muscle involvement with pseudohypertrophy in systemic light chain amyloidosis

Abstract

Rationale: Muscle pseudohypertrophy is a rare manifestation of light chain amyloidosis (AL) amyloidosis. Patient concerns: A 63-year-old woman presented with a 2-year history of progressive asthenia, macroglossia, dysphonia, cachexia, hypotension, paresthesia, and lower limb muscle hypertrophy. Diagnosis: Free serum lambda light chains were increased, and fat pad biopsy demonstrated Congo red-positive deposits. Additionally, electromyography showed a myopathic pattern, whereas muscle biopsy revealed amyloid deposits. A diagnosis of λAL with cardiac, renal, nervous system, and skeletal muscle involvement was established. Interventions and outcomes: The patient received 3 subsequent lines of therapy over the following 23 months, with very slow hematological remission followed by resolution of organ dysfunction. Lessons: Despite its rarity, muscle involvement should be considered in patients diagnosed with AL amyloidosis associated with unexplained muscle hypertrophy or weakness associated with macroglossia or elevated troponin T levels in the absence of clear cardiac involvement.

Systemic light chain amyloidosis myopathy responsive to daratumumab monotherapy

“…Muchtar et al [ 5 ] identified a few common features to skeletal muscle involvement in AL amyloidosis, in an observational study of a cohort of 51 patients: first, the strong association of amyloid myopathy with lambda light chain dysproteinemia; secondly, the muscle biopsy findings, characterized by rare necrotic and regenerating fibers and interstitial amyloid deposits in intramuscular blood vessels, which are consistent with previous reports [ 10 ]; lastly, the shared clinical aspects, such as proximal muscle weakness, dysphagia, macroglossia and, less frequently, muscular pseudohypertrophy or respiratory distress [ 5 , 11 , 12 ]. In addition, cardiac troponin T elevation, without evidence of cardiac involvement, might provide a clue enabling early diagnosis [ 2 , 5 ].…”