Corticosteroid-binding Globulin Dysfunction Due to Homozygous Lyon Variant in a Pediatric Patient.

Corticosteroid binding globulin (CBG) deficiency is a rare disorder with poorly understood pathophysiology and variable presentations. We report on a pediatric patient presenting with poor growth and delayed puberty who was diagnosed initially with primary adrenal insufficiency following 2 failed ATCH stimulation tests with normal CBG and low stimulated salivary (free) cortisol. Genetic testing demonstrated a homozygous variant known as CBG Lyon. The patient's 2 siblings were later diagnosed with the same homozygous variant but were asymptomatic with normal stimulated salivary cortisol. CBG deficiency or dysfunction should be considered in patients with unexplained adrenal insufficiency. Further research is needed to better understand CBG's role in cortisol physiology.