The aims of this study were to evaluate bone mineral density (BMD) and bone turnover markers in patients with type 1 diabetes and screening-identified evidence of celiac disease, i.e., celiac autoimmunity. We screened 50 consecutive type 1 diabetic patients for IgA antitissue transglutaminase to identify those with celiac autoimmunity. Eight seropositive patients were identified on this screening, and 12 patients matched for gender and age range were selected as a control group from among the type 1 diabetic patients without celiac autoimmunity. Patients and controls underwent dual-energy X-ray absorptiometry (DEXA) for measurement of bone mineral status and had their blood levels of osteocalcin, carboxy-terminal telopeptide of type I collagen (CTX), calcium, and phosphorus determined. BMD was further adjusted for height, weight, and pubertal stage. Radiographic and blood markers of bone mineralization were compared between patients and controls. BMD (Z-score) at the lumbar spine was -1.44 +/- 0.5 SD for patients and 0.04 +/- 0.2 SD for controls (P = 0.02). Bone mineral content was 37.9 +/- 4.5 g for patients and 49.4 +/- 2.6 g for controls (P = 0.049). Adjusted BMD was -0.62 +/- 0.5 SD for patients and 0.81 +/- 0.09 SD for controls (P = 0.04). After adjustment, four patients and none of the controls presented BMD < -1 SD (P = 0.01). Osteocalcin, CTX, calcium, and phosphorus blood levels were not significantly different between patients and controls. Celiac autoimmunity is associated with reduced bone mineralization in type 1 diabetic patients. The pathophysiological mechanisms and clinical relevance of this finding remain to be further investigated.