This is an autosomal dominant condition secondary to mutations in the PAX3 gene (22q36.1) in at least some patients. Changes in the same gene are responsible for types 1 and 3 of the Waardenburg syndrome (193500, 148820). In fact, the major mutation, a heterozygous C-to-G transversion, has been identified in the same codon in both CDHS and Waardenburg 3 (148820) patients.
More patients need to be genotyped to clarify the clinical features distinctive of Waardenburg types 1 and 3 (193500, 148820) and CDHS syndrome. Should we consider these conditions allelic or simply the result of variable expressivity? The appearance of the nasal root and associated structures is similar and both conditions are associated with sensorineural hearing loss. Type 3 Waardenburg syndrome (148820) often has a cleft palate and musculoskeletal deformities of the upper limbs and fingers. So far, no pigmentation changes have been reported in CDHS.