Case Report of a Myeloid Neoplasm with Pathogenic Germline Variant in DDX41 and Constitutional inv(7)(q11.2q22) Along With JAK2 Pathogenic Variant in a 9-Year-Old Patient Who Presented With Features of Essential Thrombocythemia.

Germline pathogenic variants in DDX41 have recently been described in association with myelodysplastic syndrome and acute myeloid leukemia in older populations. However, this pathogenic variant has rarely been described in the pediatric population. This report represents a novel case of newly diagnosed myeloid neoplasm in a 9-year-old patient presenting with essential thrombocythemia-like features and was proven to have JAK2 V617F pathogenic variant, constitutional balanced paracentric inversion on q-arm of chromosome 7, and a germline heterozygous DDX41 pathogenic variant. This is the first reported case of a pediatric patient who presented with the constellation of these clinical features, histologic findings, and genetic alterations.