A 27-year-old man was admitted to our hospital with the complaint of back pain. Bone mineral density evaluation revealed severe osteoporosis. The causes for secondary osteoporosis, such as thyrotoxicosis, glucocorticoid therapy, hypercortisolemia, hypercalciuria, and hyperparathyroidism were excluded. Laboratory examination revealed hypoglobulinemia. Further evaluation of the immunoglobulin levels was compatible with panhypoglobulinemia. The patient's vitamin D level was also low. The patient was first suspected of having a common variable immune deficiency, but he had not not experienced frequent infections. By carefully evaluating his chest x ray, a lytic lesion in his left humerus was observed. He did not have anemia and elevated sedimentation rate was not observed. Protein electrophoresis showed hypoglobulinemia. Haematology consultation was requested and a bone marrow aspiration was performed. Bone marrow examination revealed multiple myeloma with a myeloma cell increase of 70 to 80%. The patient was diagnosed as having nonsecretory myeloma which explained his hypoglobulinemia. Myeloma may cause severe osteoporosis, pain and hypercalcemia. A chemotherapy regimen (vincristine, adriablastina, dexamethasone) was initiated and further autologous stem cell transplantation was planned. The patient had also chromosome 13 abnormality. Osteoporosis at a young age especially in young men should always be extensively evaluated.