The disease is not easily definable. The main form of diagnosis is presumptive, if the person has the usual triad of preaxial polydactyly with cutaneous syndactyly of at least one limb, macrocephaly, and hypertelorism. However, a definitive diagnosis can be made if there is a phenotype that is caused by a<unk>  and a Gli3 gene mutation. It can also be made if the person has a family member or relative with the disease. Possibly, antenatal ultrasound can detect macrocephaly, and a high-resolution ultrasound can detect polydactyly and syndactyly. There are a lot of differential diagnoses, including over 100 syndromes and disorders that can cause polydactyly. However, there are a few diseases with an overlap that is significant. These diseases include: acrocallosal syndrome, carpenter syndrome, and Gorlin syndrome.
Greig cephalopolysyndactyly syndrome
Ectrodactyly–ectodermal dysplasia–cleft syndrome
Tricho–rhino–phalangeal syndrome type 2
Laron syndrome
Pott disease
Singleton Merten syndrome
Fox–Fordyce disease
Scott syndrome