OMIM ID:
Ablepharon-Macrostomia Syndrome
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
The clinical features of this syndrome remain to be fully delineated. Important ocular anomalies include malformations and sometimes absence of the upper and lower eyelids. The eyelashes and eyebrows may be sparse or even missing. The lid fissures, if present, may be shortened. Deformities of the eyelids can lead to corneal exposure and secondary vision loss.
Systemic Features
Other facial malformations include macrostomia which may be secondary to aberrant lip fusion. Micrognathia has been described. The external ears are often rudimentary, sometimes described as rosebuds. The nasal bridge is low and the nostrils anteverted. The zygomatic arches may be absent. The nipples are often missing as well. Scalp hair is sparse or even absent while the skin is dry, coarse, and often has redundant folds (cutis laxa). Mild skin syndactyly, camptodactyly, finger contractures, and shortening of metacarpals have been noted. The genitalia are often ambiguous and some patients have had ventral hernias. Hearing loss can be a feature. Growth retardation has been seen but developmental delays if present are mild. Intelligence can be normal.
Genetics
Inheritance
The majority of sibships suggest autosomal recessive inheritance although autosomal dominant inheritance has been proposed for several. One male child has been reported to have a partial deletion of chromosome 18 but other complex rearrangements were also present.
An amino acid substitution (lysine) in the basic domain of the TWIST2 gene has been found in seven families in which ablepharon-macrostomia followed an autosomal dominant pattern. Mutations in the same TWIST2 domain but leading to substitutions of glutamine or alanine amino acids is responsible for the Barber-Say phenotype (209885).
Mutations in the TWIST2 gene may also be responsible for Setleis syndrome (227260).
Pedigree
Autosomal recessive
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.