Dapsone and schistocytes: Thrombotic microangiopathy or not?

INTRODUCTION: Dapsone is used in many infectious and immunological diseases. Dapsone may cause haemolysis, particularly in individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency. This hemolysis is described as oxidative and is usually not associated with the presence of schistocytes. PATIENTS AND METHODS: We conducted a single-centre retrospective observational study at the University Hospital of Tours, France (2005-2021). Adult patients who received dapsone and had a blood smear performed during treatment or within 7 days of discontinuation were included. Data were extracted from electronic medical records. Patients were classified as schistocyte-positive (≥0.1%) or -negative. Descriptive statistics were used; no further analyses were performed due to small sample size. RESULTS: During the 2005-2021 period, 19 adult patients received dapsone in our institution. Amongst them, 10 (52.6%) had detectable schistocytes, ranging from 2 to 44/1000 erythrocytes (13 ± 14.2). Patients with schistocytosis exhibited more severe hemolytic anemia, with a larger decrease in hemoglobin (-2.7 ± 1.4 g/dL vs -1.6 ± 2.12 g/dL), higher methemoglobinemia (5.2% vs 1.9%), more frequent low haptoglobin levels (88.9% vs 60%), and elevated LDH levels (557 U/L [239-671] vs 273 U/L [208-507]) compared to patients without schistocytosis. Platelet counts were similar between the two groups. No organ failure was identified in the reviewed medical records. Schistocytosis regressed upon discontinuation of treatment after 3-18 days. CONCLUSION: Dapsone appears to be associated with hemolytic anemia and the presence of schistocytes, suggesting mechanical intravascular haemolytic anaemia. Whether Dapsone-associated biological thrombotic microangiopathy can be associated with target organ damage requires further investigation.