BACKGROUND
Amyloid light-chain amyloidosis is the most common form of systemic amyloidosis; however, it remains a rare disease. It is most often associated with non-malignant plasma cell dyscrasias but may also occur with multiple myeloma. Both conditions predominantly affect older adults. We report an unusual case of amyloid light-chain amyloidosis associated with multiple myeloma in a middle-aged adult, to highlight the diagnostic challenge posed by delayed recognition followed by severe multisystem complications.
CASE REPORT
A 41-year-old man presented with a 4-year history of constitutional symptoms, inflammatory arthralgias, bilateral carpal tunnel syndrome, nephrotic-range proteinuria, and progressive multisystem involvement. Initial immunologic and infectious investigations were negative. Systemic amyloidosis was suspected, but the patient was lost to follow-up. Reassessment demonstrated monoclonal lambda free light chains and multiple characteristic echocardiographic findings suggestive of cardiac amyloidosis. Before hematologic evaluation was completed, he developed an acute ischemic stroke followed by cardiac arrest. During hospitalization, he developed bilateral scleromalacia perforans and, days later, upper gastrointestinal perforation complicated by septic shock, leading to death. Congo red-positive minor salivary gland biopsy findings, together with bone marrow biopsy demonstrating lambda-restricted plasma cell infiltration, monoclonal protein studies, and multiple osteolytic lesions, established the diagnosis of systemic amyloid light-chain amyloidosis associated with multiple myeloma.
CONCLUSIONS
This case highlights the importance of considering amyloid light-chain amyloidosis and plasma cell disorders in middle-aged adults with nephrotic-range proteinuria and multisystem infiltrative features despite an atypical age at presentation. Although a single case cannot establish causality, delayed recognition may be followed by severe, potentially life-threatening complications in advanced multisystem disease.

Keywords: Amyloidosis; Intestinal Perforation; Multiple Myeloma; Scleritis; Stroke