Systemic mastocytosis (SM) is a myeloid neoplasm characterised by a clonal proliferation of mast cells. SM poses a diagnostic challenge due to the myriad clinical signs and symptoms that patients can present with, often evolving over time. A 78-year-old male presented with microscopic haematuria and a computed tomography intravenous pyelography revealed incidental sclerotic changes in the left pelvic bones, suspicious for Paget’s disease of the bone. Five years later, he was found to have macrocytic anaemia and subsequently developed thrombocytopenia, for which he was managed conservatively. Over the next year, he developed a maculopapular rash over the upper extremities and trunk. Bone marrow aspirate and biopsy was performed due to persistent bicytopenia. The trephine biopsy showed osteosclerosis of the trabecular bone and multiple paratrabecular aggregates of spindle-shaped mast cells. On immunohistochemistry, the mast cells were positive for CD117 and tryptase and showed aberrant expression of CD25 and CD30. Targeted sequencing identified a KIT exon 17 D816V mutation. Serum tryptase was elevated and a subsequent skin biopsy showed a dermal infiltrate of atypical mast cells. The final diagnosis was aggressive systemic mastocytosis. In conclusion, maintaining a high index of clinical suspicion is necessary for the diagnosis of SM.
Garcia et al. (Sun,) studied this question.