With M-protein positive, could transthyretin amyloidosis be easily excluded? Not necessarily! Wild-type transthyretin amyloidosis with Waldenström’s macroglobulinaemia: a case report

BACKGROUND: Generally, it is said that amyloid light-chain (AL) develops not only in multiple myeloma but also in Waldenström’s macroglobulinemia. We experienced a case of M-protein positive and diagnosed as wild-type transthyretin amyloidosis (ATTRwt) accompanied with Waldenström’s macroglobulinemia. CASE SUMMARY: The patient was 72-year-old male, and the main complaint was dyspnoea in April 2020 and visited a nearby doctor. He was introduced to the Department of Haematology at our hospital for high levels of serum immunoglobulin M, M-protein positivity, and cardiac hypertrophy with a suspect of AL amyloidosis. Duodenal mucosal biopsy and abdominal skin biopsy showed no amyloid deposits, and left iliac bone marrow biopsy diagnosed Waldenström’s macroglobulinemia and with no amyloid, and Kumamoto criteria score 1. Last of all, ATTRwt was diagnosed for endocardial biopsy. DISCUSSION: This is a very rare case of ATTRwt with Waldenström's macroglobulinaemia.