Splenic myeloid metaplasia in warm autoimmune hemolytic anemia (wAIHA): a retrospective study

Background Splenic myeloid metaplasia (SMM) is a kind of extramedullary hematopoiesis, whereas its clinical significance in wAIHA remains unclear. The aim of this study is evaluating the frequency and clinical characteristics of SMM, compared with splenic-congestion (SC). Methods We included patients with wAIHA treated in a Mexican tertiary hospital between January 1992 and December 2015. All patients received steroids as first-line treatment and splenectomy as second-line treatment. Results Among the thirty-six splenectomized patients, 15 (41.6%) and 21 (58.4%) were diagnosed as SMM and SC, respectively. No differences were found in clinical characteristics between two groups. SMM patients showed lower platelet count (147 x 10(9)/L vs. 240 x 10(9)/L, P=0.02) and higher presence of anti-dsDNA antibodies (40% vs. 4.7%, P=0.01) than SC patients. Although the complete response (CR) rate with first-line treatment was lower in SMM patients (13.3% vs. 47.6%; P=0.04), post-splenectomy median disease-free-survival (DFS) was longer (16.2 mo vs. 5.1 mo; P=0.19). Univariate/multivariate analysis showed that achieving CR during first-line treatment (OR 0.3, 95% CI: 0.03. 0.94, P=0.03) and higher platelet count (OR 0.99, 95% CI: 0.98. 0.99, P=0.03) were protective factors for SMM; and anti-dsDNA titer higher than 9.6 IU/dL was a risk factor for SMM (OR 2.76, 95% CI: 1.48. 5.14, P<0.001). Conclusion The wAIHA patients with SMM have different biological profiles with those without SMM. This study is the first trial evaluating the significance of histopathological spleen findings and their association with rheumatologic profile.