This is an autosomal dominant disorder resulting from a mutation in the FOXC1, a transcription factor gene located at 6p25. Mutations in the same gene also cause iris hypoplasia/iridogoniodysgenesis (IGDA) (IRID1) 601631) which is sometimes reported as a unique disorder but is either allelic or the same disorder as the type of Axenfeld-Rieger syndrome discussed here.
Type 1 Axenfeld-Rieger syndrome (180500) results from mutations in the PITX1 transcription factor gene and type 4 from mutations in PRDM5, also a transcription factor gene. However, digenic cases have also been reported with mutations in both PITX1 and FOXC1 genes.
The mutation responsible for type 2 Axenfeld-Rieger syndrome (601499) has as yet not been identified. Diagnosis is best made by ruling out mutations in PITX1 and FOXC1 although it is claimed that maxillary hypoplasia and umbilical defects are less common in type 2.