A Novel Alb Varient With Familial Dysalbumiemic Hyperthyroxinemia

Introduction: Familial dysalbuminemic hyperthyroxinemia (FDH) is a rare genetic disorder characterized by elevated total thyroxine (TT4) and free T4 due to an abnormal albumin binding. The disease is associated with a specifc variant in ALB gene (Arg218His). Here, we report the first Indian case of FDH with a novel variant. Case: A 61-year-old female presented with a 5-year history of temporal headaches, initially diagnosed as subclinical hypothyroidism and treated with thyroxine replacement. Serial thyroid function tests showed elevated Total T4 in all and free T4 in the majority of the assay platforms. MRI pituitary was normal. Genetic testing identified a novel rare variant in ALB gene. Family screening revealed similar thyroid function test results in both the sons who had the same variant whereas the brother with normal thyroid function tests did not have the variant. The variant was classified as likely pathogenic. She was diagnosed to have FDH. Conclusion: We report the first Indian patient with FDH due to a novel variant in ALB gene. The report expands the genetic spectrum of FDH. Variable total T4 and free T4 levels in different immunoassay platforms in FDH helps to distinguish it from TSH secreting pituitary adenoma and thyroid hormone resistance.