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Greig cephalopolysyndactyly syndrome is characterized by macrocephaly with a broad and prominent forehead and polysyndactyly. Typical findings in the limbs are postaxial polydactyly of the hands (postaxial polydactyly type B, such as a small digit attached by a skin tag to the medial border of digit V) and preaxial polydactyly of the feet (duplication of the hallux). However, other combinations are possible with variable expressivity. The thumbs/halluces may be broad or partially duplicated. Postaxial polydactyly may be complete or more subtle, consisting of only a vestigial digit along the lateral aspect of the limb. Syndactyly primarily affects fingers III and IV but is variable, ranging from near complete webbing to fully separated digits. In the feet, toes I–III are most often affected. Syndactyly is usually cutaneous but may also be osseous. Craniofacial anomalies include high forehead and frontal bossing, macrocephaly, hypertelorism, and downward slanting palpebral fissures. Learning disabilities and absence or hypoplasia of the corpus callosum may be present. Mild degrees of hydrocephalus occur at low frequency.

Bardet–Biedl syndrome (BBS) is characterized by polysyndactyly, mild to moderate psychomotor delay, mild to moderate intellectual disability, retinopathy developing during childhood, abnormalities of the renal system, hypogonadism, and obesity. Polysyndactyly is an almost consistent finding, with a frequency of 93–98 %. The polydactyly is usually of postaxial type and asymmetric, but it can also be preaxial. One to four limbs can be affected. Syndactyly occurs between the 2nd and 3rd toes as well as between the polydactylous fingers or toes. The hands and feet are broad. Typical abnormalities of the renal system are symmetrical parenchymal reduction, fetal lobulation, noncommunicating cysts, and diverticula. Further renal anomalies include hypoplasia and hydronephrosis as well as focal scarring. Primary hypogenitalism is an almost consistent finding in males. Females show a broader spectrum of genital abnormalities, such as vaginal atresia and hydrometrocolpos. Obesity usually develops in infancy. Visual impairment starts to develop in the first and especially in the second decade and progresses to total blindness. Renal failure and myocardial infarction have been described as the major causes of death in BBS.

Mirror-image polydactyly refers to a duplication of all or most digits along a central axis (mirrored). In these cases, the thumb/hallux is in the center of the hand/foot, and the digits V are at the lateral sides. This may occur either as a complete duplication with 10 or more digits or as a partial duplication with several additional digits. Mirror-image polydactyly can occur as an isolated trait (in this case usually unilateral) or as part of a syndrome. Laurin–Sandrow syndrome has been described as the combination of mirror polysyndactyly of hands and feet together with facial anomalies involving the nasal alae and columella. Preaxial and postaxial polydactyly and mirror-image polydactyly are present to variable degrees, with up to 12 digits on one extremity. Malformation and synostosis of tarsal bones are seen. The fibula and tibia as well as the ulna and radius may appear alike, suggesting a duplication of one of the stylopod bones. Mental retardation may be present. Laurin–Sandrow syndrome shows overlap with Haas-type syndactyly. Both conditions have similar cup-shaped syndactyly with polydactyly of the hands. In Haas-type syndactyly, however, the feet are relatively normal.

Triphalangeal thumb-polydactyly syndrome comprises variable forms of thumb malformation with or without syndactyly of other digits. The thumbs may be triphalangeal, duplicated, or both. The triphalangeal thumb consists of three phalanges instead of the normal two and may thus look like an index finger instead of a thumb. The phenotype is highly variable and can range from an apparently normal thumb with a small delta phalanx to a fully formed digit. Polydactyly may consist of two normal thumbs or triphalangeal thumbs or a combination. Without duplication, isolated triphalangeal thumbs are usually well formed and fully functional. Syndactyly may occur between the 3rd, 4th, and 5th fingers and is sometimes associated with bony synostosis in the distal phalanges of the same fingers. In the most severe cases, a complete syndactyly of all fingers is observed, giving a cuplike appearance to the hands. Preaxial and postaxial polysyndactyly of the feet is a common feature. No other organ manifestations or dysmorphic features are present.