000463 - Not All Cutaneous Mastocytosis Is Severe: A Pediatric Case Report

Mastocytosis is a rare disorder characterized by abnormal mast cell accumulation, most commonly affecting the skin in pediatric patients. Cutaneous mastocytosis usually presents within the first two years of life and generally follows benign course. We report a pediatric case highlighting the favorable clinical and outcome of maculopapular cutaneous mastocytosis.

We describe a 2-year-old boy referred to our hospital at 11 months of age with a previous diagnosis of cutaneous mastocytosis at a private center two months earlier. Initial evaluation included abdominal ultrasound and laboratory tests, showing normal findings and a serum tryptase level of 11.4 mcg/L. A skin biopsy was compatible with urticaria pigmentosa. The patient was born from a dizygotic twin pregnancy at 35 + 6 weeks of gestation and has an unaffected twin brother. There was no personal or family history of allergic disease.

During follow-up, the patient remained asymptomatic with no systemic manifestations, including anaphylaxis, or new cutaneous flares. Serum tryptase level decreased to 6.35 mcg/L 3 months after our first visit and remained stable at 6.75 mcg/L eleven months later. No topical corticosteroids or oral antihistamines were required. Physical examination revealed diffuse skin involvement (Figure A, B) with a positive Darier’s sign (Figure C).

This case illustrates that maculopapular cutaneous mastocytosis in early childhood can follow a favorable and benign course despite extensive skin involvement. Careful clinical monitoring and serial serum tryptase assessment are essential, but aggressive diagnosis or therapeutic interventions may not be necessary in the absence of systemic features. This report supports the generally good prognosis of pediatric cutaneous mastocytosis and underscores the importance of individualized follow-up.