7070 Nephrolithiasis and Hypercalciuria in Adults with Osteogenesis Imperfecta

Abstract Disclosure: V.R. Simões: None. M. Daly: None. M.G. Rocha-Braz: None. R.M. Martin: None. B. Ferraz-de-Souza: None. Osteogenesis imperfecta (OI) is a heterogeneous bone fragility disorder. Extra-skeletal manifestations have been well documented in children with OI, including renal complications, but studies in adults lack. Here we investigate the prevalence of nephrolithiasis and hypercalciuria in adults with OI.After informed consent, adult patients with OI attending a tertiary clinic were included in this prospective study. Disease severity score, mobility score, BMD, and molecular diagnosis, if available, were registered. Evaluation of nephrolithiasis comprised history, dietary record, and medication and supplement use. Imaging was performed in all patients with renal US and/or CT, and laboratory investigations encompassed serum (Ca, P, ALP, 25OHD, PTH, CTX, P1NP) and 24-h urine (Ca, P, citrate, oxalate, sodium, uric acid) analyses. IBM SPSS v20 was used for statistical analysis.In total, 94 adults (57 F, 37 M) with OI were evaluated, with ages ranging from 21-76 yr (50% between 20-29). Molecular diagnosis was available for 61 subjects, 79% of whom had collagen defects. Most subjects had moderate to severe OI (70%) and 48% required walking support/aid or did not walk. Excessive total (diet + supplement) daily calcium intake was identified in only 6%. Renal CT and US were available for 50 subjects (53%), CT only for 11 (12%) and US only for 33 (35%). Nephrolithiasis was identified in 26 subjects (28%). Of those, 13 (14%) had symptoms. A trend towards a higher occurrence of nephrolithiasis in subjects with moderate/severe OI was identified (p=0.059), and, reassuringly, no association with calcium intake or use of supplements was seen. ROC curve analysis revealed that 24-h U Ca >144.25 mg and 24-h U citrate 19 mg (p=0.047). Nephrolithiasis was identified in 28% female and 27% male subjects. Because nephrolithiasis is usually more common in males, analyses were repeated according to sex. In female subjects, nephrolithiasis was significantly associated with OI severity (p=0.01) and with higher mean OI severity scores (p=0.001). Strikingly, hypercalciuria (defined as 24-h U Ca >200 mg) was identified in 36% of the cohort. Significant but weak positive correlations between 24-h