A diagnosis of systemic mastocytosis (SM) was delayed for 6 years in a patient who suffered from unexplainable skin rashes, according to a case report published in Case Reports in Oncology.

The authors detailed the case of a 40-year-old male patient with chronic itchy skin lesions. The rash, which initially appeared 6 years prior, would become itchier upon touch or hot showers. Over the years, the patient sought medical advice from several doctors who prescribed topical creams without establishing a clear diagnosis.

He denied any drug or food allergies, episodes of anaphylaxis, fever, flushing, abdominal pain, shortness of breath, palpable lumps, or weight loss.

The physical examination showed multiple brown maculopapular skin lesions, measuring 5 to 10 mm in diameter, over the trunk and extremities, There were no palpable lymph nodes or hepatosplenomegaly.

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Next, the authors performed a 4-mm skin punch biopsy. The results revealed aggregates of neoplastic mast cells in the papillary dermis (>15 mast cells in the aggregates), positivity for CD117, and negativity for melanocytic markers.

The patient was referred to a hematology clinic for additional investigation. Several tests were performed, including peripheral blood analysis, renal and liver function tests, fluorodeoxyglucose (FDG)-positron emission tomography (PET), bone marrow aspiration and biopsy, and flow cytometry.

The peripheral blood tests revealed normal levels of hemoglobin, leukocytes, and platelets, as well as a normal peripheral smear. On the other hand, the level of tryptase remained slightly increased. An FDG-PET scan showed moderately increased diffuse bone marrow uptake, with no abnormal uptake to suggest high-grade malignancy. The renal and liver function tests were within normal limits.

The bone marrow aspirate was cellular, with trilineage hemopoiesis, few dysplastic forms, and 1% blasts. It identified approximately 1% of abnormal mast cells with kidney-shaped nuclei, irregular granule distribution, hypogranulation, and spindle forms.

Moreover, flow cytometry discovered approximately 1% of myeloid blasts and less than 0.1% of mast cells aberrantly expressing CD25 and partial CD2. Bone marrow biopsy revealed fair cellularity with trilineage hemopoiesis and few aggregates of phenotypically abnormal mast cells, positivity for CD117, mast cell tryptase, and aberrant positivity for CD25.

“In the absence of hepatosplenomegaly and lymphadenopathy, these findings would be compatible with indolent systemic mastocytosis. The case was discussed in a multidisciplinary team meeting, and the panel recommended managing his symptoms with an oral antihistamine with symptom-trigger avoidance,” Alshurafa and colleagues wrote. “Also, the panel recommends monitoring for osteopenia and osteoporosis as patients with all forms of systemic mastocytosis are at risk of bone disease ranging from mild osteopenia to severe osteoporosis.”

Given the rarity of SM and the plethora of conditions that may cause skin rash, many doctors struggle with establishing an accurate diagnosis. As a result, patients risk further disease progression and life-threatening anaphylactic reactions.


Alshurafa A, Abu-Tineh M, Ibrahim FA, Petkar M, Yassin MA. Delayed diagnosis of indolent systemic mastocytosis as the cause of unexplained skin rash: a case reportCase Rep Oncol. 2023;16:62-68. doi:10.1159/000529347