Abstract

Abstract Long‐term outcomes in classic galactosemia (CG) have been studied previously, but all prior studies have relied on cohorts of patients that were small in number, or heavily skewed toward children and young adults, or both. Here, we extend what is known about the health and well‐being of maturing adults with CG by analyzing the results of anonymous custom surveys completed by 92 affected individuals, ages 30–78, and 38 unaffected sibling controls, ages 30–79. The median age for patients was 38.5 years and for controls was 41 years. These study participants hailed from 12 different countries predominantly representing Europe and North America. Participants reported on their general life experiences and outcomes in seven different domains including: speech/voice/language, cognition, motor function, cataracts, bone health, psychosocial well‐being, and gastrointestinal health. We also queried women about ovarian function. Our results indicated a prevalence of long‐term complications across all outcome domains that aligned with levels previously reported in younger cohorts. Given the sample size and age range of participants in this study, these findings strongly suggest that the adverse developmental outcomes commonly linked to CG are not progressive with age for most patients. We also tested four candidate modifiers for possible association with each of the outcomes followed, including: days of neonatal milk exposure, rigor of dietary galactose restriction in early childhood, current age, and home continent. We observed no associations that reached even nominal significance, except for the following: cataracts with neonatal milk exposure ( p = 2.347e−04), cataracts with age ( p = 0.018), and bone health with home continent ( p = 0.03).