Skin as a Window to Systemic Disease: A Case of Systemic Amyloidosis Unmasked through Dermatologic Findings

Monoclonal gammopathies represent a diverse group of disorders characterised by the clonal proliferation of plasma cells and the overproduction of monoclonal proteins. Cutaneous involvement occurs in approximately 30–40% of immunoglobulin light chain (AL) amyloidosis cases and may provide crucial diagnostic clues. We present a case of a 61-year-old man who initially presented with progressive dyspnoea, fatigue, weight loss and distinctive cutaneous lesions, including asymptomatic waxy papules on the hands and extensive ecchymoses on the arms, chest and periorbital regions. Echocardiography revealed severe left ventricular dysfunction, and laboratory studies demonstrated renal dysfunction. Dermatologic evaluation led to a skin biopsy, which revealed amyloid deposits confirmed by Congo red staining and apple-green birefringence under polarised light. Subsequent bone marrow biopsy identified a plasma cell dyscrasia with markedly elevated free lambda light chains, confirming systemic AL amyloidosis. This case highlights the diagnostic significance of dermatologic findings in systemic diseases by facilitating early recognition and management of AL amyloidosis.