An 11-year-old girl presented for evaluation of multiple pruritic lesions. The lesions began when she was two or three years of age. Over time, they evolved to become fixed and increased in number. The patient had severe pruritus and flushing of her face. Her medical history was significant for frequent headaches, a one-year history of diarrhea, and one episode of difficulty breathing that was associated with exertion and required evaluation by emergency medical services. 

Physical examination revealed multiple small, tan macules and papules on the anterior and posterior neck (Figure 1), postauricular surfaces, and bilateral axillae. A few were also seen on the abdomen.

Question

Based on the patient's history and physical examination findings, which one of the following is the most likely diagnosis?

• A. Atopic dermatitis.

• B. Cutaneous mastocytosis.

• C. Idiopathic anaphylaxis.

• D. Neurofibromatosis 1.

• E. Xanthoma.

Discussion

The answer is B: cutaneous mastocytosis. Mastocytosis refers to a heterogeneous group of conditions characterized by excess production and accumulation of mast cells within the skin (cutaneous mastocytosis) or other organs such as the bone marrow, gastrointestinal tract, or skeletal system (systemic mastocytosis).¹ Cutaneous mastocytosis accounts for about 90% of cases in children.¹ Onset typically occurs before two years of age, but lesions may be present at birth.² Cutaneous mastocytosis can be categorized into maculopapular cutaneous mastocytosis (formerly known as urticaria pigmentosa; 75% of cases), solitary mastocytoma (20%), and diffuse cutaneous (5%).^2,3