Table 4.

Disorders Associated with Postaxial Polydactyly in the Differential Diagnosis of GLI3-Related Pallister-Hall Syndrome

GeneDisorderMOIClinical FeaturesComment
≥26 genes incl:
ARL6
BBS1
BBS2
BBS4
BBS5
BBS7
BBS9
BBS10
BBS12
CEP290
CFAP418
MKKS
SDCCAG8
TTC8		Bardet-Biedl syndrome (BBS)AR 1Primarily characterized by retinal cone-rod dystrophy, obesity & related complications, postaxial polydactyly, cognitive impairment, hypogonadotropic hypogonadism &/or genitourinary malformations, & renal malformations &/or renal parenchymal diseaseOverall, BBS is much more common than PHS. It is possible that atypical BBS that resembles PHS may be more common than GLI3-related PHS. BBS-related genes should be evaluated in persons w/overlapping findings.
DHCR7 Smith-Lemli-Opitz syndrome (SLOS)ARCharacterized by prenatal & postnatal growth restriction, microcephaly, moderate-to-severe ID, & multiple major & minor malformations (incl postaxial polydactyly & 2-3 syndactyly of toes). SLOS is caused by an abnormality in cholesterol metabolism.
MKKS McKusick-Kaufman syndrome (MKS)ARTriad of hydrometrocolpos in females & genital malformations in males, PAP or central polydactyly, & CHDMost non-Amish persons w/MKS evolve into the BBS phenotype in older childhood or adulthood.
SMO SMO-related hypothalamic hamartoma-polydactyly (OMIM 241800)ARHypothalamic hamartomas w/variable degrees & types of polydactylySome persons w/this disorder may be properly considered to have SMO-related PHS.
TBX5 Holt-Oram syndrome (HOS)ADUpper-limb defects, CHD, & cardiac conduction disease. Upper-limb malformations may be unilateral, bilateral/symmetric, or bilateral/asymmetric & range from triphalangeal or absent thumb(s) to phocomelia.

AD = autosomal dominant; AR = autosomal recessive; CHD = congenital heart disease; ID = intellectual disability; MOI = mode of inheritance; PAP = postaxial polydactyly; PHS = Pallister-Hall syndrome

1.

Bardet-Biedl syndrome (BBS) is typically inherited in an autosomal recessive manner.

From: GLI3-Related Pallister-Hall Syndrome

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