AL amyloid arthropathy and cardiomyopathy presenting with progressive symmetrical fixed flexion deformities and new onset congestive heart failure

Abstract

Dear Editor, A 73-year-old man was admitted with new-onset congestive heart failure and renal dysfunction. He had a 1–2 year history of a symmetrical deforming polyarthropathy characterized by persistent stiffness and progressive fixed flexion deformities, particularly of the fingers and knees. Examination revealed cachexia and generalised symmetrical muscle wasting. Bony swelling was present in the small and large joints with firm non-tender prominences over the volar aspect of both wrists. There was no clinical evidence of synovitis. X-rays of the wrists revealed significant soft tissue swelling with erosions and extensive subchondral cysts within the carpi, adjacent radii and ulna (Fig. 1). Joint spaces were preserved with only subtle subchondral sclerosis. A transthoracic echocardiogram revealed a restrictive cardiomyopathy (ejection fraction 26%). Cardiac magnetic resonance imaging (Fig. 2a) demonstrated increased biventricular and biatrial wall thickness (especially of the atrial septum), biatrial dilatation and bilateral pleural effusions (*). There was global, “ring-like” subendocardial hyperenhancement in the late gadolinium enhancement images (Fig. 2b; arrows; RV, right ventricle; LV, left ventricle). An endomyocardial biopsy revealed homogenous eosinophilic material within blood vessel walls and the interstitium, surrounding individual myocytes with associated myocyte atrophy. This stained positively for Congo red with apple-green birefringence under polarised light (Fig. 3). Serum electrophoresis was unremarkable. A serum free light chain ratio was at the upper limit of normal considering his renal function (kappa:lambda 3.12). Urine electrophoresis demonstrated trace monoclonal kappa free light chain making AL amyloidosis the most likely diagnosis. A bone marrow biopsy demonstrated a slight plasmacytosis (4%) with a high proportion of cells expressing kappa light chains (10%). His serum uric acid was 0.58 mmol/L, troponin T 0.163 μg/L and N-terminal pro-brain natriuretic peptide (NT-proBNP) 15 926 ng/L, giving an estimated prognosis of 4 months.1 A palliative approach was pursued. Although no biopsy was performed of his periarticular cysts, amyloid light-chain arthropathy was felt to be the most likely aetiology of his joint disease.