Mastocytosis is an accumulation of clonal mast cells within tissues, most commonly due to an activating KIT mutation. 1,2 The KIT gene encodes a transmembrane tyrosine receptor expressed on a variety of cell types, including mast cells. Typically, this receptor is activated by the stem cell factor ligand, but KIT mutations may result in unregulated activation of these receptors on mast cells resulting in aberrant cell activation, differentiation, proliferation, and survival. The aspartic acid to valine substitution at codon 816 of exon 17 (D 816 V) mutation constitutively activates KIT, causing clonal proliferation of mast cells. Although this mutation is found in the majority of patients with adulthood-onset mastocytosis, most pediatric mastocytosis patients will demonstrate mutations in other exons. In a study of KIT sequencing from cutaneous biopsies of 50 children with mastocytosis, 86% of patients had mutations in KIT, with the D 816 V mutation occurring in 35% of patients. The internal tandem duplication of the Ala502Tyr503 pair (dup A 502 Y 503 )mutation occurred in only 4% of patients. 1 There is currently little published information regarding the phenotype of the dup A 502 Y 503 mutation, which also causes ligand-independent activation of KIT.The study described above included two children with this mutation, both males, one of whom presented at birth with lesions consistent with maculopapular cutaneous mastocytosis and a second who presented at 1 year of age with lesions consistent with diffuse cutaneous mastocytosis (DCM). 1In this report, we describe a case of DCM in a neonate, specifically with dup A 502 Y 503 as the causative mutation. We review current data regarding appropriate work-up of DCM in neonates and discuss our management strategy for this neonate.
| C A S E REP ORTAn 11-day-old Caucasian boy presented with large, tense blisters on both hands that appeared overnight. He was otherwise in good health, with normal vital signs, appropriate feeding, voiding, and activity levels. He was delivered at 39 weeks by a healthy
AbstractMastocytosis is an accumulation of clonal mast cells within tissues, commonly caused by mutations in the KIT proto-oncogene. This report describes the management of a neonate with diffuse cutaneous mastocytosis (DCM) caused by a rare activating KIT mutation, specifically internal tandem duplication of the Ala502Tyr503 pair on exon 9, and reviews current data regarding work-up of DCM in pediatric patients.
K E Y W O R D Sc-KIT, diffuse cutaneous mastocytosis, KIT, mastocytosis | 487