AN UNUSUAL TRANSITION FROM CUTANEOUS TO SYSTEMIC MASTOCYTOSIS IN A PEDIATRIC PATIENT

Abstract

<h3>Introduction</h3> Cutaneous mastocytosis (CM) occurs when abnormal mast cells accumulate in the skin whereas in systemic mastocytosis (SM), accumulation also occurs in organs such as the gastrointestinal tract, liver, spleen, or bone marrow. A transition from CM to SM has not been previously described in the pediatric population. <h3>Case Description</h3> An eight-month-old female presented with a three-month history of diffuse hyperpigmented macules over her entire body and was found to have a normal tryptase level of 7 ug/L, consistent with a diagnosis of CM. At 2.5 years of age, cutaneous lesions significantly increased prompting repeat tryptase level, which was elevated at 34 ug/L. Subsequent testing for serum KIT D816V mutation was negative. Over the next six months, tryptase levels continued to increase (43 and 46 ug/L), raising concern for systemic involvement. At 3 years of age, repeat serum KIT D816V mutation testing resulted positive, prompting performance of a bone marrow biopsy. Bone marrow analysis revealed mildly hypocellular marrow, trilineage hematopoiesis, and aberrant mast cell clusters (>15 cells per aggregate expressing KIT, CD2, and CD25 on flow cytometry) without evidence of malignancy. These findings diagnosed SM. The patient has been treated with an antihistamine regimen, carries an epinephrine autoinjector, and has been advised on avoidance of potential triggers of mast cell degranulation. <h3>Discussion</h3> A diagnosis of CM in a pediatric patient does not rule out the possibility of transformation to SM. Despite normal baseline tryptase levels, minimal mediator symptoms, and lack of organomegaly, frequent and watchful monitoring may be warranted in some patients.