A 48-Year-Old Man With a Hip Fracture and Skin Rash: A Case Report.

Background/Objective: Patients with systemic mastocytosis are at high risk of developing osteoporosis and fractures. Herein, we report a case of hip fragility fracture in a patient with indolent systemic mastocytosis and normal bone density. Case Report: A 48-year-old man experienced a left femoral neck fracture after a fall. After a dose of oxycodone/hydromorphone postoperatively, he developed an anaphylactic reaction. Previously, he experienced a few other episodes of flushing, dizziness, and syncope precipitated by stress and alcohol. His examination was notable for pink and brown macules on his chest, back, arms, and legs. His laboratory test revealed a markedly elevated tryptase level of 171 ng/mL (<11 ng/mL). Treatment including cetirizine, montelukast, and ranitidine controlled his symptoms. His bone density test result was normal. Ten months after hip surgery, his c-terminal telopeptide of collagen type 1 and bone-specific alkaline phosphatase levels significantly increased. The bone scan demonstrated diffusely increased radiotracer uptake throughout the osseous structures. Given high bone turnover and the prior hip fracture, he received zoledronic acid yearly for 3 years, and no further fractures have occurred. Discussion: The case is unusual as the fracture occurred despite normal bone density and significant osteosclerosis, which was previously considered protective against fractures. Additionally, rather than the spine, the fracture occurred in the hip, which is an uncommon site for mastocytosis-induced fractures. Conclusion: Mastocytosis is a rare cause of osteoporosis, and it is important to keep this condition in the differential diagnosis of osteoporosis, particularly when the fracture presentation is atypical.