Indolent Systemic Mastocytosis – a Case Report

Abstract Indolent systemic mastocytosis is a benign form of systemic mastocytosis characterized by an abnormal proliferation of mast cells either in the bone marrow or in numerous tissues. Case Report: A 27-year-old female patient was admitted to our department due to urticaria which started a month ago. Before the skin changes appeared, our patient suffered from a toothache, so she took various painkillers (nimesulide, ibuprofen, acetylsalicylic acid, paracetamol). During skin examination, individual hyperpigmented macules on the trunk and lower limbs were observed as incidental findings. The patient reported having them for the last two years. Darier's sign was positive. Following the examination, she was admitted due to suspected urticaria pigmentosa. Laboratory Findings: erythrocyte sedimentation rate: 9 mm/h; complete blood count, urine, blood glucose, total and direct bilirubin, aspartate aminotransferase, alanine aminotransferase, gamma-glutamyl transferase, urea, creatinine, and uric acid were within normal ranges. Electrolytes: sodium, potassium, chlorine clearance, total calcium and calcium ionized, osteocalcin, and crosslaps were within normal ranges as well. Fibrinogen: 5.57 g/l; 5-Hydroxyindoleacetic acid: 49.8 umol/dU (10.4 - 31.2). Bone densitometry, chest x-ray and upper abdomen ultrasound findings were normal. The suspected clinical diagnosis of urticaria pigmentosa was confirmed by skin biopsy. Histopathological examination of the bone marrow showed moderately increased cellularity (60 - 70%). All three types of blood cells were slightly multiplied. Focal infiltrations were found in the perivascular area, consisting of elongated, oval cells with abundant eosinophilic granular cytoplasm. The nuclei were regular, oval shaped with finely granular chromatin and inconspicuous nucleoli. No nuclear atypia was found. These cells are highly CD117-positive. This finding strongly indicated bone marrow infiltration in systemic mastocytosis. The diagnosis was based on ‘major’ and ‘minor’ diagnostic criteria. The recommended therapy included H1 and H2 antagonists and topical corticosteroids. Conclusion: Regular follow-up was recommended in order to prevent complications and malignant alterations.