Case presentation
A 48-day-old female infant was firstly hospitalized at Nan children Hospital of Nanjing medical University (Nanjing, China) in April, 2021, with a complaints of increasing pallor sign from birth. Her mother had a history of PIH during pregnancy. On the first day after birth, the newborn was treated for fever in a local hospital. Blood routine tests showed neutropenia with absolute neutrophil count (ANC) 0.04 × 109/l with no periodic changes, mild anemia, and normal platelet count. She also presented with non-pruritic, ecchymosis skin lesions on the head,chest, trunk, and extremities after birth but got a self-remission soon. At this time, laboratory evaluation demonstrated marked neutropenia again with severe anemia (WBC, 0.91 × 109 /L; ANC ,0.02 × 109 /L,hemoglobin, 3.3 g/dL; platelets, 212 × 109 /L). Coombs test were negative. LDH level was normal. Physical examination revealed severe anemia, while no skin lesions and lymphadenopathy were found.
She was treated by infusion of erythrocytes but complicated with a severe allergic reaction. Blood transfusion was immediately stopped, epinephrine and hydrocortisone were given, and transferred to ICU for other life-supporting treatment.Anemia screening revealed ferritin 524ng/ml, folic acid and vitamin B12 at normal levels; reticulocyte ratio and absolute count were within the normal range;We performed bone marrow biopsy and without positive result. Based on the above examination and the past medical history of the infant, we first ruled out hemolytic anemia and nutritional deficiency anemia and chronic disease anemia;We also completed peripheral blood whole exon gene sequencing to rule out inherited metabolic diseases; while waiting for the gene results, we continued the infant’s red blood cell transfusion treatment and administered methylprednisolone before the transfusion to prevent allergic reactions; the patient’s granulocyte deficiency status gradually returned to normal after glucocorticoid administration. Therefore, the infant was discharged from our hospital for the first time and was instructed to be followed up on an outpatient basis. One week after discharge, the child’s anemia worsened again. During this recurrence, he was treated with methylprednisolone 10mg once a day daily for four weeks, and hemoglobin gradually recovered again .At this point, the whole-exon gene sequencing results suggested a mutation in the KMT2C gene[Figure2] , but this was not sufficient to explain the symptoms of allocytopenia in the infant.
She experienced a worsening bruise-purple nodular skin rash, and pancytopenia two months later. BM smears demonstrated that blastic or abnormal cells accounted for 3.5% of the nucleated cells[Figure1 C/D] . Flow cytometry revealed a small population of blasts in the dim CD45 positive blast gate that were positive for CD4, CD56, CD123, and HLA-DR but the negative expression of B, T, myeloid marker, and TdT[Figure2] . A skin biopsy was done, and the results revealed diffuse dermal infiltrate with blast-like cells extending to the hypodermis. Immunohistochemistry revealed cells positive for CD4, CD31,CD68,CD43,CD56, and CD123 but negative for CD3,CD20, MPO, TDT, CD34, and EBER, confirming the blastic plasmacytoid dendritic cell neoplasm diagnosis[Figure1] . Her parents disregarded the advice to take chemotherapy, and she died just a month after being diagnosed.