Chromosome affected: 7p13
Gene affected: GLI3 transcription factor
GCPS can be difficult to diagnose because its findings overlap with those of other conditions.
Criteria for definitive diagnosis - both of the following:
(1) all of the following phenotypic findings ("classic triad"):
(1a) preaxial polydactyly AND cutaneous syndactyly affecting at least 1 limb
(1b) hypertelorism
(1c) macrocephaly
(2) one or both of the following:
(2a) mutation in GLI3 identified on molecular analysis
(2b) one or more family members who have been definitively diagnosed with GCPS AND an autosomal dominant pattern of inheritance
where:
• Polydactyly = increased numbers of digits
• Cutaneous syndactyly = attachment between digits due to persistent skin webs
The presence of criterion 1 without 2 allows for presumptive diagnosis of GCPS.
