A recent series of case reports published in the journal Biomolecules highlights how unexplained or hard-to-treat osteoporosis — weak, thinning bones — can be an early warning sign of systemic mastocytosis (SM), and should prompt a thorough checkup that includes a blood 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. test and 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. even when there are no skin symptoms at all.
The case series describes four adults who were referred to a specialist bone clinic because they had osteoporosis that either had no clear cause or would not improve with treatment. None of the four had any skin changes — a common sign of SM that doctors often look for first.
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To work out why their bones were so weak, doctors measured a substance in the blood called tryptase, which reflects the number of mast cells (a type of immune cell) in their body. In every case it came back high. That result led doctors to take a sample from inside the bone — a bone marrow biopsy — and run a genetic test for a change called KIT D816V. Based on this test, all four were diagnosed with SM. Three had the subtype indolent SMIndolent SM A subtype of nonadvanced SM caused by the abnormal accumulation of mast cells in the bone marrow and other organs. Indolent SM accounts for around 90% of SM cases. (ISM), and the fourth had SM with associated hematological neoplasm (SM-AHN) with 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 behaved indolently.
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All four patients were treated with intravenous zoledronic acid to strengthen their bones, along with vitamin D — in line with what current guidelines recommend. At the time the paper was published, too little time had passed to say how the patients’ bones will do over the long run.
A key lesson from these cases is that “the absence of skin lesions does not exclude the diagnosis [of SM],” the authors said. In these patients, weak bones were sometimes the only clue to mastocytosis, and a routine tryptase test was the step that led to the diagnosis.
The authors suggested bone disease in mastocytosis should be further researched. “Larger prospective studies are needed for better screening and treatment practices for osteoporosis-presenting indolent SM,” they noted.
