Breaking point: Systemic mastocytosis manifesting as severe osteoporosis.

Systemic mastocytosis (SM) encompasses a wide spectrum of myeloproliferative disorders defined by the aggregation of abnormal mast cells in various tissues, including the bone marrow, gastrointestinal tract, liver and lymph nodes. The release of tryptase, interleukins and cytokines by the accumulated mast cells causes a multi-system response that can range from mild flushing and pruritus to severe anaphylactic reactions, gastrointestinal disturbances, and cardiovascular symptoms, including hypotension and syncope. Furthermore, severe osteoporosis manifesting as bone-lytic lesions or pathologic fractures due to mast cell mediator-triggered bone resorption, is a rather common manifestation of SM, occurring in more than two-thirds of patients. The vast majority of SM cases harbor the D816V KIT mutation, which is an independent prognostic factor, and serves as a therapeutic target. This is a rare case of a young male who presented with new-onset back pain due to osteoporotic fractures and was diagnosed with SM without the D816V KIT mutation. Our case aims to emphasize one of the most underrecognised causes of osteoporosis in adults, and to shed light on a frequently misdiagnosed yet potentially severe hematologic disorder.