BACKGROUND: Refeeding syndrome is the gravest possible medical complication in malnourished patients undergoing refeeding in the hospital. We previously reported that males with malnutrition secondary to eating disorders required more calories and had longer hospital stays than females; however, sex differences in electrolyte abnormalities indicating refeeding syndrome risk remain unknown. The objective of this study was to assess differences in electrolyte abnormalities indicating refeeding syndrome risk among male and female adolescents and young adults with eating disorders hospitalized for medical instability. METHODS: We retrospectively reviewed the electronic medical records of 558 patients aged 9-25 years admitted to the University of California, San Francisco Eating Disorders Program for medical instability between May 2012 and August 2020. Serum was drawn per standard of care between 5 and 7 am each morning and electrolyte abnormalities indicating refeeding syndrome risk were defined as: hypophosphatemia (< 3.0 mg/dL), hypokalemia (< 3.5 mEq/L), and hypomagnesemia (< 1.8 mg/dL). Logistic regression was used to assess factors associated with electrolyte abnormalities indicating refeeding syndrome risk. RESULTS: Participants included 86 (15.4%) males and 472 (84.6%) females, mean (SD) age 15.5 (2.8) years. Rates of refeeding hypophosphatemia (3.5%), hypokalemia (8.1%), and hypomagnesemia (11.6%) in males hospitalized with eating disorders were low, with no statistically significant differences from females. Older age was associated with higher odds of refeeding hypophosphatemia and hypomagnesemia. Lower percent median body mass index and greater weight suppression at admission were associated with higher odds of refeeding hypophosphatemia. CONCLUSIONS: Rates of electrolyte abnormalities indicating refeeding syndrome risk were low in males hospitalized for eating disorders and rates did not significantly differ from females. Together with our finding that males have higher caloric requirements and longer hospital length of stay, the finding that electrolyte abnormalities indicating refeeding syndrome risk were not greater in males than females supports future research to evaluate the safety and efficacy of higher calorie and/or faster advancing refeeding protocols for males.

Ankylosing spondylitis (AS) is a common, highly heritable, inflammatory arthritis for which HLA-B*27 is the major genetic risk factor, although its role in the aetiology of AS remains elusive. To better understand the genetic basis of the MHC susceptibility loci, we genotyped 7,264 MHC SNPs in 22,647 AS cases and controls of European descent. We impute SNPs, classical HLA alleles and amino-acid residues within HLA proteins, and tested these for association to AS status. Here we show that in addition to effects due to HLA-B*27 alleles, several other HLA-B alleles also affect susceptibility. After controlling for the associated haplotypes in HLA-B, we observe independent associations with variants in the HLA-A, HLA-DPB1 and HLA-DRB1 loci. We also demonstrate that the ERAP1 SNP rs30187 association is not restricted only to carriers of HLA-B*27 but also found in HLA-B*40:01 carriers independently of HLA-B*27 genotype.