Evaluation of genotype-phenotype relationships in patients referred for endocrine assessment in suspected Pendred syndrome.
[pendred syndrome]
Design: Patients with Pendred syndrome have genotypic and phenotypic variability, leading to challenges in definitive diagnosis and deaf children with enlarged vestibular aqueducts are often subjected to repeated investigations when tests for mutations in SLC26A4 are abnormal. This study provides genotype and phenotype information from patients with suspected Pendred syndrome referred to a single clinical endocrinology unit. Methods: Retrospective analysis of 50 patients with suspected Pendred syndrome to investigate the correlation between genetic, perchlorate discharge test (PDT) and endocrine status. Results: Eight patients with monoallelic mutations had normal PDT. Of the 33 patients with biallelic mutations, 10 of 12 patients with >30% discharge developed hypothyroidism. In our cohort, c.626G>T and c.3-2A>G result in milder clinical presentations with lower median perchlorate discharge of 9.3% (interquartile range 4-15%) compared to 40% (interquartile range 21-60%) for the remaining mutations. Eight novel mutations were detected. All patients with PDT <30% remained euthyroid to date, although the majority are still under age 30. There was a significant correlation between PDT and size of goitre (R=0.61, p=0.0009) and the age of onset of hypothyroidism (R=-0.62, p=0.0297). In our population, the hazard of becoming hypothyroid increased by 7% per percentage point increase in PDT (P<0.001). Conclusion: There is correlation between SLC26A4 genotype and thyroid phenotype. If results hold true for larger patient numbers and longer follow-up, then for patients with monoallelic mutations, PDT could be unnecessary. Patients with biallelic mutations and PDT discharge >30% have high risk of developing goitre and hypothyroidism, and should have lifelong monitoring.
