A case report recently published in Cureus describes a 42-year-old woman who developed an unusual form of cutaneous mastocytosisMastocytosis Rare disease caused by the buildup of mast cells. Cutaneous mastocytosis primarily affects the skin and is more common in children, while systemic mastocytosis affects internal organs and is more common in adults. that was doubly rare: unlike most adults with mastocytosis, she had large, irregular skin lesions and no signs of systemic mastocytosis (SM).
Mastocytosis that is limited to skin symptoms (cutaneous mastocytosis) is usually seen in children; 95% of adults with cutaneous mastocytosis symptoms are found to have underlying SM. The appearance of skin lesions also usually differs between adults and children. In adults, skin spots are usually small and uniform, while in children they are larger with more variation in size and shape (called polymorphic). The polymorphic maculopapular cutaneous mastocytosis (MPCM) variant seen in this case is rare in adults.
The authors noted the woman initially developed increasing hyperpigmentation over her breast that did not improve with topical triamcinolone, a steroid medication. She subsequently developed hyperpigmented lesions across her chest and abdomen. Biopsies of two lesions showed increased perivascular and interstitial mast cells.
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Over the following month, more hyperpigmented macular lesions measuring 1 mm to 5 mm appeared on her arms and face. She also experienced intermittent flushing in her face and chest, itching and a positive Darier’s sign, which occurs when a lesion swells into a hive after being rubbed.
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The flushing episodes were triggered by hot showers and emotional stress but were not accompanied by respiratory, cardiovascular, gastrointestinal or other systemic symptoms. She also did not report fatigue, weight loss, fever, night sweats, diarrhea, pathologic fractures, osteopenia or osteoporosis.
Because adult cutaneous mastocytosis is so often associated with SM, doctors performed more tests to look for signs of systemic disease. A bone marrow biopsyBone marrow biopsy A procedure to collect a sample of bone marrow using a needle. Often used to examine the characteristics of mast cells and diagnose SM. showed no dense mast cellMast cell A type of white blood cell produced in the bone marrow. They help defend against infections and play a key role in allergic reactions. In SM, mast cells become overactive and build up throughout the body. infiltrates or abnormal mast cells and was negative for CD2, CD25 and CD30 expression and the KIT D816V mutation. Testing for KIT D816V in peripheral blood using droplet digital PCR was also negative. Her baseline serum tryptaseTryptase A protein enzyme that is primarily produced by mast cells and stored in small pockets within the cells, known as granules. High levels of tryptase are a key indicator of SM. remained within the normal range, ranging from 2.9 to 4.0 ng/mL.
Based on the clinical and biopsy findings, along with the absence of the major and minor diagnostic criteria for SM, the authors diagnosed her with adult-onset polymorphic MPCM without systemic involvement.
They treated the woman with cetirizine and montelukast to control symptoms. They also recommended continued allergy follow-up and serial baseline tryptase testing, as systemic involvement could potentially develop over time.
“In adult patients presenting with a polymorphic macular cutaneous eruption, it is important to keep MPCM in the differential diagnosis,” the authors concluded. “If punch biopsy of the lesions is consistent with cutaneous mastocytosis, the evaluation for underlying SM should be completed, even in the absence of overt extracutaneous symptoms.”
Read more about skin symptoms: “Can mastocytosis spots be removed?”
