Familial dysalbuminemic hyperthyroxinemia (FDH) due to Arg242 His variant in ALB gene in Turkish children

OBJECTIVES

To investigate ALB gene variations in patients suspected from familial dysalbuminemic hyperthyroxinemia (FDH).

METHODS

Eight Turkish patients were included into the study. Clinical and laboratory characteristics of the subjects and their parents were evaluated and genetic analysis were performed.

RESULTS

In genetic analysis, a previously reported heterozygous, c.725G>A variant was detected in exon seven of the ALB gene.

CONCLUSIONS

FDH is an asymptomatic condition however there is still a risk of misdiagnosis and unnecessary treatment. Therefore, if FDH is considered, initial ALB hotspot sequencing as a rapid and simple method is recommended instead of complex and expensive laboratory and imaging techniques.

Familial dysalbuminemic hyperthyroxinemia combined with Graves' disease: a rare case report

BACKGROUND

Familial dysalbuminemic hyperthyroxinemia (FDH) is an autosomal dominant disease characterised by an abnormally increased affinity of albumin for serum thyroxine. Assay interference and differential diagnosis remain challenging for FDH. The condition is more complicated when FDH is combined with primary thyroid diseases. Co-occurrence of FDH and Graves' disease is rare.

CASE PRESENTATION

We report the case of a 28-year-old woman with complex FDH and coexisting Graves' disease. Initially, the existence of FDH was not recognised. Graves' disease was relieved after treatment with antithyroid drugs and two administrations of radioactive iodine therapy. She subsequently developed primary hypothyroidism and was prescribed levothyroxine replacement. However, thyroid function failed to normalise despite frequent levothyroxine dose adjustments. Ultimately, syndromes involving the inappropriate secretion of thyroid-stimulating hormone (IST) were considered, and FDH was successfully differentiated from other causes of IST.

CONCLUSIONS

A greater focus on FDH when investigating the causes of IST is critical to correctly evaluate thyroid function status and avoid inappropriate treatment, especially in complicated cases with concurrent FDH and primary thyroid diseases.

Familial Dysalbuminemic Hyperthyroxinemia (FDH), Albumin Gene Variant (R218S), and Risk of Miscarriages in Offspring

BACKGROUND

Familial dysalbuminemic hyperthyroxinemia (FDH) is a rare autosomal dominant disorder whose clinical characteristics remain incompletely understood, we investigated the role of albumin gene mutation in relation to miscarriage rate in a large pedigree of FDH followed up for 4 years.

PATIENTS AND METHODS

The proband and extended family with unexplained miscarriage and hyperthyroxinemia were identified and genotypes in candidate genes and thyroid function tests (TFTs), including changes in TFTs during pregnancy were comprehensively assessed. We also evaluated the development and growth of children in this large FDH pedigree during four years follow-up.

RESULT

The R218S variant in the albumin gene was identified in the proband and her relatives with hyperthyroxinemia who were diagnosed as FDH. Among the family members who underwent TFTs, 11 of 17 (65%) had similar changes in levels of thyroid hormone, with an estimated FDH heritability of 86%. Moreover, 32% (95% CI 16-54%) of FDH women experienced miscarriages at a rate that was substantially higher than the spontaneous abortion rate reported in the general population in China (7-14%). During the follow-up, results revealed that free triiodothyronine (fT3) and thyroid stimulating hormone (TSH) levels were normal during the entire gestational period; comparing to their age-adjusted peers, both FDH affected and FDH unaffected children in this pedigree appeared to have lower body weight and height.

CONCLUSIONS

Albumin gene variant (R218S) not only causes FDH but also may be associated with a higher risk of miscarriages, although the growth of their children appears not to be affected by the age of 2 years.

Clinical recognition and evaluation of patients with inherited serum thyroid hormone-binding protein mutations

There are three important thyroid hormone-binding proteins in human serum, thyroxine-binding globulin, transthyretin, and albumin. Genetic variation in these proteins can lead to altered thyroid hormone binding and abnormalities in serum tests of thyroid hormone. Importantly, patients harboring these mutations are euthyroid; thus, the recognition of these conditions is crucial to prevent unnecessary repeated testing and treatment. This article provides an updated overview of serum thyroid hormone transport biology and reviews the underlying genetic alterations, clinical presentation, and appropriate evaluation of patients with suspected mutations in serum thyroid hormone-binding proteins.

First Report of Familial Dysalbuminemic Hyperthyroxinemia With an ALB Variant

Familial dysalbuminemic hyperthyroxinemia (FDH) is an inherited disease characterized by increased circulating total thyroxine (T4) levels and normal physiological thyroid function. Heterozygous albumin gene (ALB) variants have been reported to be the underlying cause of FDH. To our knowledge, there have been no confirmed FDH cases in Korea. We recently observed a female patient with mild T4 elevation (1.2 to 1.4-fold) and variable levels of free T4 according to different assay methods. Upon Sanger sequencing of her ALB, a heterozygous c.725G>A (p.Arg242His) variant was identified. The patient's father and eldest son had similar thyroid function test results and were confirmed to have the same variant. Although the prevalence of FDH might be very low in the Korean population, clinical suspicion is important to avoid unnecessary evaluation and treatment.