A new case study reports on a 61-year-old Vietnamese man with delayed-onset diffuse cutaneous mastocytosis without systemic disease. The case study, published in Baylor University Medical Center Proceedings, noted that the patient had 3 risk factors for systemic mastocytosis: urticaria pigmentosa, elevated tryptase level, and a history of venom-induced anaphylaxis due to an insect bite.

“Cutaneous mastocytosis is a rare disease, mostly manifested in adults as urticaria pigmentosa, diffuse and erythrodermic mastocytosis, and telangiectasia macularis eruptive perstans,” the authors wrote.

“It is important to evaluate the clinical pattern at presentation as well as laboratory markers and consider a bone marrow biopsy for a specific diagnosis.”

The man presented with a 10-year history of chronic generalized cutaneous eruption, along with 1 anaphylactic reaction to an ant bite for which he was prescribed an EpiPen. He had extensive brown papules and macules located on his torso and arms, and rubbing them produced an urticarial wheal, consistent with Darier’s sign.

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A shave biopsy revealed significantly increased mast cell numbers, hyperpigmentation of the basal layer, and CD-177-positive mast cells, verifying the mastocytosis diagnosis. Although the patient presented with several risk factors for systemic mastocytosis, in the genetic analysis, he had a normal karyotype and KIT D816 was not detected.

In addition, blood tests revealed that his serum tryptase level was only mildly elevated. Thus, the presence of systemic mastocytosis was ruled out.

The authors note that the presence of cutaneous symptoms such as urticaria pigmentosa typically lead to a suspicion of mastocytosis, but in the absence of such symptoms, the diagnosis can be delayed or missed. For cases with a history of anaphylactic reactions, they recommend lifelong venom immunotherapy to reduce the risk of anaphylaxis and improve quality of life.


Cavazos A, Subrt P, Tschen JA. Delayed diagnosis of adult-onset mastocytosis. Proc (Bayl Univ Med Cent). Published online June 7, 2022. doi:10.1080/08998280.2022.2081914