Osteoporosis as the sole manifestation of systemic mastocytosis in a young man

Objective: To highlight the difficulty involved in making a diagnosis of systemic mastocytosis (SM) when it manifests solely as osteoporosis. Methods: We present a detailed case report and review the literature regarding the work-up of secondary osteoporosis and the diagnosis and treatment of SM. Other cases of SM presenting as osteoporosis in male patients are also described. Results: A 35-year-old man presented with back pain after weight lifting and was diagnosed with a T7 vertebral compression fracture. A dual-energy x-ray absorptiometry scan resulted in a T-score of -3.2 in the spine and of -1.9 and -2.4 in the hip and femoral neck areas, respectively. Results of standard tests for secondary osteoporosis including calcium, phosphorus, 25-hydroxyvitamin D, kidney and liver function, thyroid function, testosterone level, and midnight salivary cortisol were normal. Further testing revealed a high serum tryptase level of 26.8 μg/L (reference range, <11.4) and elevated urinary histamine at 39.1 μg/g creatinine (reference range, <35). Bone marrow biopsy confirmed the diagnosis of mastocytosis. Conclusion: The rare diagnosis of SM is difficult when there is little clinical suspicion and remains a challenge to endocrinologists and other physicians. The condition should be suspected in young male patients with no other obvious cause of osteoporosis.