Screening of the eleven congenital hypothyroidism-related genes demonstrated a previously reported nonsense DUOXA2 mutation (p.Tyr138<sup>*</sup>) in the homozygous state.
After the identification of thyroid H<sub>2</sub>O<sub>2</sub> generation system (DUOX) and of its maturation factors (DUOXA), defects in DUOX2 and/or DUOXA2 were rapidly recognized as the possible cause of congenital hypothyroidism (CH) due to thyroid dyshormonogenesis.
Seven different recurrent mutations [p.G488R (n=13), p.A649E (n=3), p.R885Q (n=3), p.I1080T (n=2), and p.A1206T (n=2) in DUOX2; p.Y138X (n=9) in DUOXA2; and p.R450H (n=5) in TSHR) were identified as the mutations underlying CH.
We identified a novel DUOXA2 mutation (I26M) causing CH with goiter, which affected H2O2 generation but did not alter the protein expression levels, further confirming the essential role of DUOXA2 in thyroid hormone synthesis.
More recently, additional diseases have been linked to functionally altered variants in genes encoding for other NADPH oxidases, such as for DUOX2/DUOXA2 in congenital hypothyroidism, or for the Nox2 complex, NOX1 and DUOX2 as risk factors for inflammatory bowel disease.
Biallelic loss-of-function mutations of DUOX2 result in congenital hypothyroidism (CH), whereas a single reported case of homozygous DUOXA2 mutation (Y246X) has been associated with mild CH.