3. Evaluation of bone mineral content (BMC) and bone turnover. At baseline and every six months we will measure BMC of the whole body, hip and spine using DXA. Results will be compared to those from age-matched normal children whose results are archived in the body composition laboratory of Dr. Ken Ellis (Children's Nutrition Research Center, Houston). At baseline and every six months we will also measure bone mineral turnover markers including: osteocalcin, bone specific alkaline phosphatase activity, and deoxypyridinoline. All findings will be related to cytokine levels and to use of glucocorticoids. This specific aim tests the hypothesis that bone density is low in chronically ill children secondary to increased osteoclast activity correlating with elevated cytokine levels.