Lead Toxicity Masquerading as Autoimmune Haemolytic Anaemia: A Diagnostic Pitfall in Unexplained Anaemia

Lead toxicity is an uncommon but clinically important cause of unexplained anaemia. Its heterogeneous haematological manifestations can mimic autoimmune haemolytic anaemia, resulting in diagnostic uncertainty and delayed recognition. A 49-year-old woman presented with a three-week history of worsening abdominal pain and lethargy. She had a background of inclusion body myositis treated with long-term intravenous immunoglobulin and recent initiation of mycophenolate mofetil. Initial investigations demonstrated severe anaemia with reticulocytosis but minimal biochemical evidence of haemolysis. A weakly positive direct antiglobulin test (IgG 1+, C3d negative) raised suspicion for autoimmune haemolysis. The initial peripheral blood film was reported as showing marked red cell agglutination without additional abnormalities. Progressive anaemia prompted extensive investigations, including infectious, immunological, and haematological workups, all of which were unremarkable. Bone marrow aspirate demonstrated atypical plasma cells, prompting re-examination of the peripheral blood film, which revealed Pappenheimer bodies and basophilic stippling. Further history identified ingestion of an unlabelled health supplement, and toxicology testing confirmed markedly elevated blood lead levels. Chelation therapy with succimer led to clinical and haematological improvement. Public health investigation subsequently confirmed the supplement as the source of lead and mercury exposure. This case highlights lead toxicity as an important but under-recognised mimic of autoimmune haemolytic anaemia. Careful review of peripheral blood morphology and a thorough exposure history are essential when evaluating unexplained anaemia with an inconclusive haemolysis workup.