Familial Dysalbuminemic Hyperthyroxinemia Induced by Mutation R218H of Albumin

Abstract

Familial Dysalbuminemic Hyperthyroxinemia (FDH) is thought of no clinical significance, but tends to to misdiagnosed and mistreated as Graves’ hyperthyroidism with long time. In a Chinese family to explore clinical characteristics, hereditary features and gene variation of FDH and its effect on pregnancy. Methods: Two propostitus (a father and his son) with hyperthyroidism were re-diagnosed as FDH due to the canonical profile of measured thyroid hormones. After screening thyroid function of the whole family, eight affected of FDH were identified among total thirteen lineal relatives. They were studied in terms of clinical history, biochemical and hormone examination, thyroid imaging and TSH secreting test by dexamethasone and bromocriptine. Three members accepted gene analysis with the next generation sequencing followed by Sanger method. Productive history was investigated in five spouse of the whole family. Results: In the two propostitus, FDH exhibited very high total thyroxine (T4) and mild high total triiodinethyronine (T3), and normal free T4 and T3 besides normal thyroid stimulating hormone (TSH). In addition, ultrasound discovered diffuse goiter and enhanced blood flow, and 99mTc uptake increased, while TSH receptor antibody and pituitary MRI scan remained normal. Other six family members had similar changes of the thyroid hormones and normal TSH which could be suppressed dramatically by dexamethasone and bromocriptine, then were suspected of FDH and thereafter confirmed with gene analysis. Among these eight FDH, four were misdiagnosed with hyperthyroidism and mistakenly received anti-thyroid medication at least one year. Gene analysis of three members revealed R218H variation of albumin gene. Conclusions: R218H associated FDH shows canonical changes of thyroid hormones with increased thyroid function, high penetrance and misdiagnose rate with hyperthyroidism, it exerts no effect on pregnancy.