Osteoporosis can be the first sign of systemic mastocytosis (SM), according to a study recently published in Oncoscience.
“SM should be considered in any patient with unexplained osteoporosis, chronic gastrointestinal symptoms or idiopathic anaphylaxis,” the authors wrote.
The case report describes a 23-year-old man with lower back pain that had become worse over time and led to difficulty walking. He did not have any recent history of injury. The patient had previously been diagnosed with glucose-6-phosphate dehydrogenase (G6PD) deficiency (a genetic condition that can cause hemolytic anemia) and multiple sclerosis, which was being treated with ozanimod.
Initial imaging showed that the patient had a fractured spine and severe osteoporosis. Laboratory tests found he had anemia and elevated white blood cells (leukocytosis). Notably, the patient’s calcium, vitamin D and thyroid function levels were all normal.
Given the inconclusive results, the authors ran additional testing and found he had elevated serum tryptase and C-terminal telopeptide of collagen, which raised suspicion for SM. A bone marrow biopsy confirmed the diagnosis of SM with abnormal tryptase, CD117 and CD30-positive mast cell infiltration of 15-20%. However, further genetic testing was negative for the KIT D816V mutation, a mutation present in over 90% of patients with SM. The patient was offered a broader molecular analysis, but he declined.
The patient was diagnosed with an aggressive form of SM per the 2022 World Health Organization criteria. He began treatment with zolendronic acid, vitamin D supplementation, and systemic therapy with avapritinib, as well as a spinal brace.
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The coexisting G6PD deficiency in this case also required careful pain management selection to avoid hemolysis, with ibuprofen being chosen as a safer alternative.
This case exhibits the challenge of diagnosing a patient with SM-related osteoporosis. SM is one of “the most underrecognised causes of osteoporosis in adults,” the authors noted.
The lack of KIT D816V mutation was also notable. “Further studies are needed to explore KIT 816SM without the D816V mutation, due to its distinct clinical characteristics and variable treatment responses,” the authors concluded.
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