Endocrine Abstracts

JOINT810

Background: Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED; autoimmune polyendocrine syndrome type 1), a genetic disease with hypoparathyroidism, primary adrenocortical insufficiency (PAI), chronic candidiasis and other autoimmune manifestations. Our previous study showed that a severe APECED phenotype associated with changes in bone microarchitecture.

Objective: This study aimed to explore muscle characteristic in relation to bone properties in patients with APECED.

Patients and Methods: We recruited 37 adults with APECED and 82 age- and gender-matched control subjects. In both groups, we assessed muscle and bone characteristics at the proximal site of tibia (38%) with peripheral quantitative computed tomography (pQCT). In the patient group, dual-energy absorptiometry (DXA) was also used to measure total muscle mass and whole-body bone mineral density (BMD). Mann-Whitney or Student’s t-test was used to test for differences between the groups and Kendall’s rank test to test for correlations.

Results: Altogether 37 adult patients (22 females) participated in the study (median age 44.0, range, 19.3-70.1 years). In females with APECED, muscle area (mean, 5129.8 vs 5706.4 cm², P = 0.004) and tibial cortical thickness (mean, 4.6 vs 5.1 mm, P = 0.006) as well as height (mean, 161.4 vs 164.8 cm, P = 0.026) were smaller in comparison to control subjects. At tibial site, their muscle area correlated positively with bone area, bone density, cortical thickness, periosteum circumference, but not with height. In control females, muscle area correlated only with muscle density at tibial site. For APECED females with PAI (n = 14), muscle area at tibial site was smaller (median, 4766.9 vs 5927.6 cm², P = 0.025) than in patients without PAI (n = 4). In males with APECED, muscle area (mean, 5963.8 vs 7222.8 cm², P < 0.001) and tibial cortical thickness (mean, 5.1 vs 5.9 mm, P = 0.002) and periosteal circumference (median, 72.7 vs 78.4 mm, P = 0.012), as well as height (median, 173.0 vs 182.7 cm, P = 0.003) were smaller in comparison to control males. There were no correlations between muscle area and any tested bone parameters at tibial site in males with APECED or in control males. DXA-derived values showed no correlation between total muscle mass and whole-body BMD in females or males with APECED. However, muscle area in pQCT at tibial site correlated with whole body BMD in DXA (τ=0.621, P < 0.001) in females but not in males with APECED. Significance Our findings show that the inferior bone parameters in subjects with APECED are associated to some extent with muscle properties. Physical performance testing could shed light to clinical implications of these findings.