Marked Drop in Bone Density in One Area


Question

I would like to request an expert opinion on a bone and mineral metabolism case, and ask for your assistance in directing my question to an expert you feel would be most appropriate in addressing this case. 60 year old man with osteoporosis, with unremarkable evaluation for secondary causes of decreased BMD (normal CBC, TSH, testosterone, ESR, PTH/calcium, creatinine, serum protein electrophoresis, 25 OH vit.D), treated with Actonel 35 mg weekly with calcium 1000 mg/day and vit. D 400-800 u/day. Follow-up DXA scan 2 years later showed decrease in BMD of 8% for lumbar spine, and stable proximal femur BMD. Why was there a signficant "disconnect" between lumbar spine and proximal femur BMD on follow up scan, and what would you advise for further diagnostic/therapeutic interventions? Thank you.Bill Jou, M.D.Arcadia, CA

Response

The most likely explanation here is instrument error, since this much of a disconnect is unusual. If that is not the explanation, then one would need to look harder for an underlying process. You have appropriately excluded significant vitamin D deficiency, hyperparathyroidism, etc. However, if you are convinced that this is not due to some type of instrument error (ie either the initial or f/u spine BMD is erroneous), I would recommend obtaining a bone marrow aspirate and biopsy to be sure there is not an underlying marrow dyscrasia (plasma cell disorder, mast cell disease, etc) that may be causing this. Sundeep Khosla MD,Mayo Clinic College of Medicine