TABLE 2.

Trinucleotide repeat disorders with varying penetrance depending on the number of repeats present.

Disease	Gene	STR	Non-penetrant	Intermediate penetrance	Full penetrance
Spinocerebellar ataxia 8	ATXN8OS/ATXN8 (Perez et al., 2021)	CTG/CAG	<91	92–106	>107
Spinal muscular atrophy	SNM1 (Laskaratos et al., 2021)	CAG	<34	35–46	>47
Fragile X	FMR1 (Hagerman et al., 2017)	CGG	<44	45–200	>200
Huntington’s	HTT (Kay et al., 2016)	CAG	<36	37–39	>40
ALS	C9orf72 (DeJesus-Hernandez et al., 2011)	GGGGCC	<23	24+	>700
Friedrich’s Ataxia	FXN (Kim et al., 2011)	GAA	<34	35–99	>100