Unexplained Pancytopenia in a Patient with 5q35.2-q35.3 Microduplication Encompassing NSD1: A Case Report

The 5q35.2-q35.3 duplication phenotype is characterized by growth delay, microcephaly, mental retardation and delayed bone aging. However, there has been no reports on the occurrence of pancytopenia as a consequence of 5q35.2-q35.3 duplication. A 42-year-old male visited the emergency room due to multiple trauma. He had been diagnosed with mental retardation in the past. Physical examination was unremarkable except for tenderness over bone fracture. Complete blood cell counts were leukocyte 3.51×109/L, neutrophil 0.19×109/L, hemoglobin 8.3 g/dL, hematocrit 25.0%, and platelet 4.0×109/L. There was no relevant history of any medication intake and there were no other haematological parameters leading to the persistent pancytopenia. A bone marrow biopsy revealed hypercellular marrow with increased trilineage hematopoiesis. The uptake of fluorodeoxyglucose was increased in multiple lymph nodes, bone and spleen in positron emission tomography– computed tomography. A biopsy of the right axillary lymph node was performed and histologic findings were unremarkable. The chromosomal microarray revealed a 3.46 Mb microduplication at the 5q35.2-q35.3 site including NSD1. The patient had distinctive features related to atypical pancytopenia. Various managements for pancytopenia had no effect on the patient. However, there were no complications such as massive bleeding or serious infection compared to the severity of pancytopenia during a follow-up of 3 months. In addition, periodic patterns of deterioration and improvement in pancytopenia appeared spontaneously. Since it is rare for these distinctive features of pancytopenia and chromosomal abnormality to coexist, it is important to investigate the association. In the current study, we describe the first case of 5q35.2-q35.3 microduplication encompassing NSD1 with unexplained pancytopenia.