We report a case of a 46-year-old woman suffering from 5 years of premenopausal osteoporosis due to systemic mastocytosis (SM). The only clinical symptom was severe back pain and restricted spinal movements resulting from the existing vertebral compression fractures. There were no skin lesions. Because of the severity of the case, nonresponse to the administered treatment, and the premenopausal initiation of her osteoporosis, a further investigation for an underlying cause was accomplished. Laboratory evaluations excluded metabolic or endocrinologic abnormalities. Serum tryptase was slightly elevated while urinary excretion of histamine was highly increased. A diagnostic bone marrow biopsy specimen was done and the patient fulfilled the diagnostic criteria for SM. SM should be included in the differential diagnosis in cases of unusually presented osteoporosis due to its significant morbidity and the existing treatment options.