Patients with Juvenile Rheumatoid Arthritis (JRA) often manifest generalized osteoporosis and can develop hypercalciuria with [Illegible Text]. IL-1 mediated bone resorbing activity has been demonstrated in JRA patients and proposed as mechanism of these findings. We evaluated a 16 year old white male with a connective tissue disease (CTD) clinically similar to JRA (fevers, joint pain/swelling) with a positive ANA but negative ant-double stranded DNA, presenting with hypercalcemia (serum calcium 13.1mg/dl). Joint symptoms resolved with low dose daily prednisone but hypercalcemia persisted(Ca>11.5) despite intermittent NSAID therapy. Further evaluation revealed: 1) Suppressed PTH, 2) Low normal Vitamin D metabolites, PTH-related protein, and serum phosphorous, 3) Hypercalciuria - urine Ca 11.7 mg/Kg/day(normal<4), 4) Ectopic calcification with soft tissue calcification of muscle and blood vessels of upper and lower extremities, 5) Nephrocalcinosis - severe, 6)Mild renal insufficiency - Creatinine clearance 54 ml/min/1.73m2, 7) Microhematuria, 8) Normal urinary protein excretion.
Bone resorbing activity was measured using a bone disc bioassay. Bone disc Ca uptake was measured after incubation in patient sera or PBS. Discs incubated in patient sera showed bone resorption compared to control media(p<0.001). Bone resorbing activity was eliminated by IL-1 receptor antagonist but not PTH antibody.
