A Review of the Clinical Features and Management of Systemic Congenital Mastocytosis through the Presentation of An Unusual Prenatal-Onset Case.

Mastocytosis is a heterogeneous group of rare hematological disorders that can occur in infancy. We report a 16-year-old girl who presented with an aggressive form of systemic congenital mastocytosis, associated with a significant global developmental delay, deafness, and multiple anomalies. At 4 years of age, she developed a germinoma presenting as an invasive spinal mass. Extensive cytogenetic, metabolic, and molecular genetic studies that included whole-exome sequencing studies revealed a KIT alteration (NM_000222.3(KIT):c2447A > 7 pAsp816Val) and likely pathogenic variant in the DNA from peripheral blood and skin lesions. C-kit was also found to be overexpressed in the spinal tumor cells. We compared the features of this child to those of six previously reported pediatric patients with cutaneous mastocytosis, microcephaly, microtia, and/or hearing loss reported in OMIM as mastocytosis, conductive hearing loss, and microtia (MIM 248910), for which the etiology has not yet been determined. This report extends the currently recognized spectrum of KIT-related disorders and provides clues as to the potential etiology of a syndromic form of congenital mastocytosis. International efforts to understand the benefits of long-term targeted therapy with tyrosine kinase inhibitors for this KIT-altered rare disease should continue to be evaluated in clinical trials.