A pediatric case of central diabetes insipidus and hypopituitarism after COVID-19 suspected with lymphocytic hypophysitis with positive anti-rabphilin-3A antibodies.

Lymphocytic hypophysitis (LYH) is a rare autoimmune disorder characterized by lymphocytic infiltration of the pituitary gland, leading to central diabetes insipidus (CDI) and hypopituitarism. Although distinguishing LYH from other diseases presenting with pituitary enlargement is challenging, the use of anti-rabphilin-3A antibody (RPH3A-Ab) in the diagnosis of LYH has been recently reported. Case reports of LYH following coronavirus disease 2019 (COVID-19) infection in adult and adolescent patients have been accumulated. Here, we present the first case confirming the presence of RPH3A-Abs in pediatric CDI following COVID-19. A 4-yr-old girl developed CDI one week after COVID-19, and anterior hypopituitarism was confirmed 14 mo later. Head magnetic resonance imaging (MRI) revealed progressive pituitary stalk thickening, which subsequently improved. Although other disease-specific markers did not increase, serological testing confirmed the presence of RPH3A-Ab, supporting the clinical diagnosis of LYH. It has previously reported that RPH3A-Ab demonstrate high sensitivity and specificity in differential diagnosis of LYH, and RPH3A-Ab are also identified as positive in pediatric cases of LYH with a biopsy. Additionally, this is the first documented prepubertal case of LYH following COVID-19. Our case study indicates that LYH can occur in children after COVID-19, and RPH3A-Ab may be useful in its diagnosis.