Congenital Amegakaryocytic Thrombocytopenia Presenting With Features of Immune Thrombocytopenia: A Case Report.

Congenital amegakaryocytic thrombocytopenia (CAMT) is a rare inherited bone marrow failure disorder characterized by severe thrombocytopenia due to absent or markedly decreased megakaryocytes. It typically presents in infancy and may initially mimic more common causes of thrombocytopenia, such as immune thrombocytopenic purpura (ITP), leading to delays in diagnosis. We describe the case of a young child who initially presented with isolated thrombocytopenia in early infancy and was treated as ITP. Despite multiple courses of standard ITP therapy, including corticosteroids and intravenous immunoglobulin, her platelet counts failed to improve. Over time, the development of progressive pancytopenia raised concern for an underlying bone marrow failure syndrome. Although bone marrow examination demonstrated hypocellularity, a definitive diagnosis of CAMT could not be established based on morphology alone. The diagnosis was ultimately confirmed by whole-exome sequencing, which identified a pathogenic mutation in the myeloproliferative leukemia virus oncogene (MPL) gene. This case highlights the diagnostic challenges posed by rare inherited thrombocytopenias that clinically resemble ITP. Most importantly, it underscores the limitations of bone marrow biopsy as a standalone diagnostic tool and emphasizes the critical role of genetic testing in establishing a definitive diagnosis when clinical suspicion persists. Early identification of CAMT improves long-term outcomes, prevents prolonged ineffective treatment, and facilitates timely referral for hematopoietic stem cell transplantation.