Identification of Genetic Disorders Causing Disruption of Selenoprotein Biosynthesis.

Disorders of selenoprotein biosynthesis in humans, due to mutations in three genes (SECISBP2, TRU-TCA1-1, and SEPSECS) involved in the selenocysteine insertion pathway, have been described. Patients with SECISBP2 and TRU-TCA1-1 defects manifest a multisystem disorder with a biochemical signature of abnormal thyroid function tests due to the impaired activity of deiodinase selenoenzymes, myopathic features linked to SEPN1 deficiency and phenotypes resulting from increased levels of reactive oxygen species attributable to lack of antioxidant selenoenzymes. In patients harboring SEPSECS mutations, severe, progressive, cerebello-cerebral atrophy (pontocerebellar hypoplasia type 2D) dominates the phenotype and it is not known whether the disorder is associated with thyroid dysfunction.