Cri-du-chat syndrome was first described by Lejeune et al. (1963) as a hereditary congenital syndrome associated with deletion of part of the short arm of chromosome 5. The deletions can vary in size from extremely small and involving only band 5p15.2 to the entire short arm. Although the majority of deletions arise as new mutations, approximately 12% result from unbalanced segregation of translocations or recombination involving a pericentric inversion in one of the parents.

Hypocalcified amelogenesis imperfecta is characterized by enamel of normal thickness on newly erupted and unerupted and unresolved teeth. The enamel is soft and may be lost soon after eruption leaving the crown composed only of dentin. The enamel has a cheesy consistency and can be scraped from the dentin. An anterior open bite has been recorded in over 60% of the cases observed. The hypocalcification type is the most frequent type of enamel dysplasia, occurring in about 1 in 20,000 individuals (Witkop and Sauk, 1976). Large masses of supragingival calculus become deposited on the teeth, and this is frequently associated with severe gingivitis or periodontitis (Winter and Brook, 1975).

Dentinogenesis imperfecta is a disorder of tooth development. This condition causes the teeth to be discolored (most often a blue-gray or yellow-brown color) and translucent. Teeth are also weaker than normal, making them prone to rapid wear, breakage, and loss. These problems can affect both primary (baby) teeth and permanent teeth.\n\nResearchers have described three types of dentinogenesis imperfecta with similar dental abnormalities. Type I occurs in people who have osteogenesis imperfecta, a genetic condition in which bones are brittle and easily broken. Dentinogenesis imperfecta type II and type III usually occur in people without other inherited disorders. A few older individuals with type II have had progressive high-frequency hearing loss in addition to dental abnormalities, but it is not known whether this hearing loss is related to dentinogenesis imperfecta.\n\nSome researchers believe that dentinogenesis imperfecta type II and type III, along with a condition called dentin dysplasia type II, are actually forms of a single disorder. The signs and symptoms of dentin dysplasia type II are very similar to those of dentinogenesis imperfecta. However, dentin dysplasia type II affects the primary teeth much more than the permanent teeth.

Cleft palate as an isolated malformation behaves as an entity distinct from cleft lip with or without cleft palate (see 119530). Dominantly inherited cleft soft palate in 4 generations has been reported (Jenkins and Stady, 1980); see 119570.

Amelogenesis imperfecta is an inherited defect of dental enamel formation that shows both clinical and genetic heterogeneity. In the hypoplastic type of AI, the enamel is of normal hardness but does not develop to normal thickness. The thinness of the enamel makes the teeth appear small. Radiographically, enamel contrasts normally from dentin. The surface of the enamel can vary, showing smooth, rough, pitted, or local forms (Witkop, 1988).

Autosomal recessive amelogenesis imperfecta pigmented hypomaturation type is characterized by enamel of normal thickness that is hypomineralized and has a mottled appearance. The slightly soft enamel detaches easily from the dentin, and radiographs show a lack of contrast between enamel and dentin (Witkop, 1989). Genetic Heterogeneity of the Hypomaturation Type of Amelogenesis Imperfecta See also AI2A2 (612529), caused by mutation in the MMP20 gene (604629); AI2A3 (613211), caused by mutation in the WDR72 gene (613214); and AI2A4 (614832), caused by mutation in the C4ORF26 gene (614829).

Amelogenesis imperfecta is a disorder of tooth development. This condition causes teeth to be unusually small, discolored, pitted or grooved, and prone to rapid wear and breakage. Other dental abnormalities are also possible. These defects, which vary among affected individuals, can affect both primary (baby) teeth and permanent (adult) teeth.\n\nResearchers have described at least 14 forms of amelogenesis imperfecta. These types are distinguished by their specific dental abnormalities and by their pattern of inheritance. Additionally, amelogenesis imperfecta can occur alone without any other signs and symptoms or it can occur as part of a syndrome that affects multiple parts of the body.

Autosomal recessive amelogenesis imperfecta pigmented hypomaturation type is characterized by enamel of normal thickness that is hypomineralized and has a mottled appearance. The slightly soft enamel detaches easily from the dentin, and radiographs show a lack of contrast between enamel and dentin (Witkop, 1988).

Amelogenesis imperfecta type IH is characterized by hypoplastic and hypomineralized tooth enamel that may be rough, pitted, and/or discolored (Wang et al., 2014 and Poulter et al., 2014).

Autosomal recessive amelogenesis imperfecta of the pigmented hypomaturation type is characterized by enamel of normal thickness that is hypomineralized and has a mottled appearance. The slightly soft enamel detaches easily from the dentin, and radiographs show a lack of contrast between enamel and dentin (Witkop, 1989).

Other features of auriculo-condylar syndrome can include prominent cheeks, an unusually small mouth (microstomia), differences in the size and shape of facial structures between the right and left sides of the face (facial asymmetry), and an opening in the roof of the mouth (cleft palate). These features vary, even among affected members of the same family.\n\nAbnormalities of the mandible are another characteristic feature of auriculo-condylar syndrome. These abnormalities often include an unusually small chin (micrognathia) and malfunction of the temporomandibular joint (TMJ), which connects the lower jaw to the skull. Problems with the TMJ affect how the upper and lower jaws fit together and can make it difficult to open and close the mouth. The term "condylar" in the name of the condition refers to the mandibular condyle, which is the upper portion of the mandible that forms part of the TMJ.\n\nMost people with auriculo-condylar syndrome have malformed outer ears ("auriculo-" refers to the ears). A hallmark of this condition is an ear abnormality called a "question-mark ear," in which the ears have a distinctive question-mark shape caused by a split that separates the upper part of the ear from the earlobe. Other ear abnormalities that can occur in auriculo-condylar syndrome include cupped ears, ears with fewer folds and grooves than usual (described as "simple"), narrow ear canals, small skin tags in front of or behind the ears, and ears that are rotated backward. Some affected individuals also have hearing loss.\n\nAuriculo-condylar syndrome is a condition that affects facial development, particularly development of the ears and lower jaw (mandible).

Amelogenesis imperfecta type IIIC is characterized by hypocalcified enamel in both the primary and secondary dentition. The enamel is rough and yellow-brown; under normal use, the enamel disintegrates from occlusal surfaces of the molars, leaving a ring of intact enamel remaining on the sides. Some affected individuals have anterior open bite (Kim et al., 2019).