Increased Serum-Immunoglobulin G4 Levels in a 12-Year-Old Male Patient With Central Diabetes Insipidus.

Immunoglobulin G4 (IgG4)-related disorders are characterized by tissue hypertrophy due to IgG4-positive cell infiltration and increased serum IgG4 levels. IgG4-related hypophysitis (IgG4-RH) is characterized by pituitary hypertrophy, IgG4-positive cell infiltration, central diabetes insipidus, and increased serum IgG4 levels. IgG4-RH is diagnosed through diagnostic criteria. A few cases of IgG4-RH in children have been reported. We report a case of CDI with increased serum IgG4 levels that failed to meet the diagnostic criteria of IgG4-RH. The patient developed polyuria and polydipsia at age 11 and was diagnosed as having idiopathic CDI at age 12. The patient was not treated with steroids and is well controlled with antidiuretic hormones. It has been reported that pediatric IgG4-RH differs from that of adults in several respects. We believe that the pediatric IgG4-RH may not fit the diagnostic criteria of adults. There may be also other cases of increased serum IgG4 levels in pediatric patients with idiopathic CDI. We do not know if they are subtypes of IgG4-RH or if serum IgG4 levels are by chance raised in CDI, however, we report them here because IgG4-RH in children may be different from that in adults.