INTRODUCTION
Mastocytosis describes a group of disorders with a pathologic accumulation of mast cells in various tissues. Urticaria pigmentosa is mastocytosis of the skin, which manifests as mastocytomas that can produce hives and pruritus when irritated. To our knowledge, we are reporting the first case of urticaria pigmentosa without any manifestation of pruritus.
CASE REPORT
A 27-year-old female presented to the clinic with reddish-brown macules involving all cutaneous surfaces, excluding the face, palms, and soles. Upon stroking the macules on the patient's forearm, the macules became swollen and erythematous, eliciting a positive Darier's sign (Figure 1A). A physical examination was negative for hepatomegaly and splenomegaly,
but the abdomen was mildly tender. Lymphadenopathy was not detected in the groin, axillae, inguinal, or cervical lymph nodes. Muscle strength was full and symmetric with normal tone and symmetric reflexes. Sensory testing, including vibration sense, was normal. Serum tryptase level was 28 ng/mL (RR, 0-11.4 ng/mL). The patient reported having long-standing episodic bouts of diarrhea and headaches. Moreover, the patient stated that she never feels itching and has never used an antihistamine or topical steroid. A biopsy from a lesion on the forearm demonstrated increased mast cell proliferation. Giemsa staining, immunohistochemical stains for CD117 (Figure 1B), and mast cell tryptase showed 30 mast cells in a high-powered field.
but the abdomen was mildly tender. Lymphadenopathy was not detected in the groin, axillae, inguinal, or cervical lymph nodes. Muscle strength was full and symmetric with normal tone and symmetric reflexes. Sensory testing, including vibration sense, was normal. Serum tryptase level was 28 ng/mL (RR, 0-11.4 ng/mL). The patient reported having long-standing episodic bouts of diarrhea and headaches. Moreover, the patient stated that she never feels itching and has never used an antihistamine or topical steroid. A biopsy from a lesion on the forearm demonstrated increased mast cell proliferation. Giemsa staining, immunohistochemical stains for CD117 (Figure 1B), and mast cell tryptase showed 30 mast cells in a high-powered field.
DISCUSSION
Mastocytosis is characterized by the pathologic increase of mast cells in tissues, often associated with mutations in the receptor tyrosine kinase KIT (also termed c-KIT or CD117). Mast cells originate from CD34+ progenitor cells in the bone marrow, and they contain a variety of vasoactive mediators that normally function to protect the body via inflammatory responses.1 A mutation in the KIT gene or abnormalities in KIT regulation affect the growth, differentiation, and activation of mast cells.2 In mastocytosis, there is a pathologic activation of the c-kit (CD 117) receptor, leading to unregulated clonal expansion and activation of mast cells. Mastocytosis classically presents with pruritus.
