Oral-facial-digital syndrome type I (OFD1) is usually male lethal during gestation and predominantly affects females. OFD1 is characterized by the following features: Oral (lobulated tongue, tongue nodules, cleft of the hard or soft palate, accessory gingival frenulae, hypodontia, and other dental abnormalities). Facial (widely spaced eyes or telecanthus, hypoplasia of the alae nasi, median cleft or pseudocleft upper lip, micrognathia). Digital (brachydactyly, syndactyly, clinodactyly of the fifth finger; duplicated hallux [great toe]). Kidney (polycystic kidney disease). Brain (e.g., intracerebral cysts, agenesis of the corpus callosum, cerebellar agenesis with or without Dandy-Walker malformation). Intellectual disability (in ~50% of individuals).

Hand-foot-genital syndrome (HFGS) is characterized by limb malformations and urogenital defects. Mild-to-severe bilateral shortening of the thumbs and great toes, caused primarily by shortening of the distal phalanx and/or the first metacarpal or metatarsal, is the most common limb malformation and results in impaired dexterity or apposition of the thumbs. Urogenital malformations include abnormalities of the ureters and urethra and various degrees of incomplete müllerian fusion in females, and hypospadias of variable severity with or without chordee in males. Vesicoureteral reflux, recurrent urinary tract infections, and chronic pyelonephritis may occur; fertility is normal.

Temtamy syndrome is a mental retardation/multiple congenital anomaly syndrome characterized by variable craniofacial dysmorphism, ocular coloboma, seizures, and brain abnormalities, including abnormalities of the corpus callosum and thalamus (summary by Akizu et al., 2013).

An extremely rare syndrome with characteristics of hypoplastic thumbs and halluces, fifth finger brachydactyly, postaxial polydactyly of the hands, short or uniphalangeal second toes with absent nails and hypospadias. It has been described in a father and his son and daughter. The affected patients have normal mental development. Except for postaxial polydactyly of the hands and uniphalangeal second toes with absent nails, features are in common with hand-foot-genital syndrome caused by mutations in the HOXA13 gene. In all three affected individuals, two different sequence alterations were identified in HOXA13 gene: a de novo missense mutation and a deletion in the promoter region of the gene, inherited from an unaffected parent, which may contribute to the phenotype in the affected individuals. The condition is inherited in an autosomal dominant manner.

Distal monosomy 6p is responsible for a distinct chromosome deletion syndrome with a recognizable clinical picture including intellectual deficit, ocular abnormalities, hearing loss, and facial dysmorphism.

Mitochondrial complex IV deficiency nuclear type 16 (MC4DN16) is an autosomal recessive metabolic disorder with highly variable manifestations. Common features include failure to thrive with poor overall growth, short stature, and microcephaly. Some patients additionally have neurologic involvement, including developmental regression with severe hypotonia, feeding difficulties, and seizures. Brain imaging in the more severely affected patients shows cerebral and cerebellar atrophy and abnormal lesions in the basal ganglia. In all cases, patient tissues show variably decreased levels and activity of mitochondrial respiratory complex IV (summary by Pillai et al., 2019). For a discussion of genetic heterogeneity of mitochondrial complex IV (cytochrome c oxidase) deficiency, see 220110.