It is associated with mutations in the PQBP1 gene. The gene product is a polyglutamine-binding protein involved in transcription and pre-mRNA splicing. The gene itself is located on the short arm of the X chromosome (Xp11.23). The most common mutations causing this condition occur in exon 4.
Renpenning's syndrome
Wartenberg's syndrome
Banti's syndrome
Liddle's syndrome
Villaret's syndrome
Frey's syndrome
Grisel's syndrome
Bertolotti's syndrome