ORF34-02 - Indolent Systemic Mastocytosis Presenting with Multiple Vertebral Fractures and Severe Osteoporosis in a Young Adult

Background:
This case describes a young man who presented with a sudden, severe back pain after jumping off a diving board and was later found to have multiple vertebral compression fractures far exceeding what would be expected from the reported injury. The case highlights the importance of considering secondary causes of osteoporosis early in the evaluation of young patients with unexplained fractures.

Case description:
A male in his late 30s presented after an acute onset of severe back pain after jumping off a diving board. His past medical history was significant for chronic back pain and smoking. Imaging in the ED revealed a severe T12 burst fracture with retropulsion, causing spinal canal stenosis and cord compression, along with multiple additional thoracic and lumbar compression fractures of different chronicity. He underwent emergent decompressive laminectomy, open reduction, posterior spinal fusion from T11-L1, and T12 kyphoplasty. After discharge, he underwent DXA, which demonstrated severe osteoporosis with a lumbar spine Z-score of -4.3. Due to the above changes, he was referred to endocrinology for further evaluation. Upon further questioning, he denied exposure to glucocorticoids, anticoagulants, or antiseizure medications. His work included manual labor. He denied any history of allergic reactions, urticaria, flushing, or pruritus. He did mention a nonspecific, mild maculopapular rash on his bilateral flanks of unknown chronicity. Laboratory evaluation showed normal calcium, PTH, thyroid function, urine calcium, and negative celiac serologies. Initial vitamin D was low but improved with supplementation. SPEP was normal, RF negative, and testosterone low-normal, but was done in the afternoon. Notably, alkaline phosphatase was 136 U/L (normal 46-116 ), and serum tryptase was markedly elevated on repeated testing 61.7 mcg (normal < 11.0).
Despite the absence of flushing, urticaria, or anaphylaxis, evaluation for mast cell disease was done by oncology. Peripheral blood testing for KIT D816 was negative. Skin biopsy showed superficial perivascular dermatitis with increased mast cells. Bone marrow biopsy revealed aggregates of spindled mast cells (CD117+) involving 5% of marrow space and CD25 and CD2 coexpression, consistent with indolent systemic mastocytosis. Liver imaging showed no significant organ involvement.

Conclusion:
This case demonstrates how indolent systemic mastocytosis is an important and often overlooked cause of secondary osteoporosis in young adults, even in the absence of classic mast cell-mediated symptoms. Elevated tryptase and unexplained low bone density should prompt evaluation for mast cell disorders. Early recognition and broad workup for the causes of osteoporosis is important in young adults who present with disproportionate fractures, uncommon to the mechanism of injury, and underlying osteoporosis.