PO093 | HOW LONG IS TOO LONG? A CASE OF SEVERE PERSISTENT THROMBOCYTOPENIA

B. Clerici^1|2, C. Ghali², M. Scavone², A. Fioretti², M. Perego¹, C. Mondini^1|2, E. Fiorini¹, L. Catarini¹, C. Pescia³, S. Caberlon¹, U. Gianelli^2|3, G.M. Podda^1|2 | ¹S.C. Medicina Generale SP, Ospedale San Paolo, ASST Santi Paolo e Carlo, Milano, Italy; ²Dipartimento di Scienze della Salute (DISS), Università degli Studi di Milano, Milano, Italy; ³S.C. Anatomia Patologica, Ospedale San Paolo, ASST Santi Paolo e Carlo, Milano, Italy

Background. The diagnostic differential of thrombocytopenias is wide. The periodic re-evaluation of the working diagnosis is of crucial importance, especially in the face of poor response to treatment, as 1 in 7 patients suspected of having primary immune thrombocytopenia (ITP) are misdiagnosed.
Case report. A 42-year-old woman was admitted on August 1^st, 2025, because of severe new-onset thrombocytopenia (9x10⁹/L, n.v. 150-350x10⁹/L) and moderate normocytic anemia (9.2 g/dL, n.v. 12.3-15.3 g/dL). She was symptomatic for fatigue but otherwise in good clinical condition. At the time of admission, haemolysis markers were negative and there were no immature cells or schistocytes on the peripheral blood film. We suspected ITP and started high-dose dexamethasone and intravenous immunoglobulin. Because her platelets remained at critically low levels, we started romiplostim, again with no response. Because of the poor response to ITP-directed therapies, we performed a bone marrow biopsy, which revealed increased megakaryocytes, dismyelopoiesis and MF-1 fibrosis, and ordered a PET-CT, which showed hepatosplenomegaly and multiple metabolically active lymphadenopathies both below and above the diaphragm. We performed an excisional lymph node biopsy on August 18^th. In the meantime, the patient’s clinical condition quickly worsened. She developed an abrupt increase in inflammatory markers, low-grade fever, nocturnal night sweats, worsening kidney function, a decline in her urine output and subsequent fluid overload, requiring the start of intermittent dialysis. The rapidly evolving clinical picture and the findings from the lymph node biopsy (marked hypervascularity, lymphoid follicle atresia and polyclonal plasmacellular infiltrate) rose the suspicion of TAFRO, a rare and potentially life-threatening form of idiopathic multicentric Castleman disease characterized by thrombocytopenia, anasarca, bone marrow fibrosis, renal dysfunction and organomegaly not associated with HIV, EBV or HHV-8 infection. Flow cytometry (FC) evaluations during florid disease revealed increased p-selectin positive platelets (13%, n.v. <7%), inappropriately low reticulated platelets (7%, n.v. <16%), and increased platelet desyalilation (8%, n.v. <0.2%). From August 22^nd, we started treatment with high-dose methylprednisolone, rituximab and the anti-IL6 monoclonal antibody siltuximab. With this course of treatment, the patient’s condition improved: her inflammatory markers declined until normalization, she was weaned off dialysis and her constitutional symptoms resolved. Despite this, severe anaemia and thrombocytopenia persisted, with development of intravascular haemolysis (consumed haptoglobin, increased lactate dehydrogenase and reticulocytes) and symptomatic hypertension. Disseminated intravascular coagulation, thrombotic thrombocytopenic purpura and intracranial haemorrhage were ruled out. We suspected a complement-mediated thrombotic microangiopathy (TMA) and administered eculizumab as rescue therapy on September 16^th. Unfortunately, the patient died of refractory septic shock on September 23^rd.
Conclusions. Our FC findings suggest that, during florid TAFRO, impaired megakakaryopoiesis and platelet desyalilation can contribute to thrombocytopenia. In the described case, the persistence of thrombocytopenia and the onset of neurological symptoms despite the control of the inflammatory syndrome prompted the recognition of a superimposed TMA.