Haploidentical Hematopoietic Stem Cell Transplantation in a 3-Year-Old Girl with Congenital Amegakaryocytic Thrombocytopenia: A Case Report

Congenital amegakaryocytic thrombocytopenia (CAMT) is an autosomal recessive disorder characterized by severe thrombocytopenia that presents soon after birth and is usually not accompanied by specific somatic malformations [Germeshausen M, Ballmaier M. Best Pract Res Clin Haematol 2021; 34: 101286]. CAMT is more prevalent in females than males [Ballmaier M, Germeshausen M. Semin Thromb Hemost 2011; 37: 673–681; Germeshausen M, Ballmaier M. Haematologica 2021; 106: 2439–2448], in contrast to other congenital bone marrow failure syndromes. Patients with CAMT also exhibit cardiac malformations, cerebellar hypoplasia, growth retardation, and a distinctive facial appearance [Yldrm A T, Güneş B T, Oymak Y, et al. Blood Coagul Fibrinolysis 2015; 26: 337–341], although it remains unknown whether these are related to CAMT. Mutations in the MPL gene, which encodes the thrombopoietin receptor, are the pathogenetic cause of CAMT [Germeshausen M, Ballmaier M. Haematologica 2021; 106: 2439–2448]. Since thrombopoietin is involved in the maintenance of hematopoietic stem cells and megakaryocyte development [Germeshausen M, Ballmaier M. Best Pract Res Clin Haematol 2021; 34: 101286], CAMT may eventually manifest as a hematopoietic failure. Currently, allogeneic hematopoietic stem cell transplantation (HSCT) is the only cure for CAMT. Human leukocyte antigen (HLA)-matched siblings are the first-choice donors for HSCT because transplantations from matched unrelated donors have a low success rate [King S, Germeshausen M, Strauss G, et al. Br J Haematol 2005; 131: 636–644]. Cancio et al. [Cancio M, Hebert K, Kim S, et al. Transplant Cell Ther 2022; 28: 101 e101–101 e106] reviewed 86 patients treated over 18 years and reported that although HLA-mismatched donors can extend the survival of CAMT patients, HLA-matched donors are preferred. The present report describes the successful treatment of a 3-year-old girl with CAMT using haploidentical allogeneic HSCT from the father, even though he harbored a mutant MPL gene.