Ablepharon-Macrostomia Syndrome (AMS)

At a glance

A type of ectodermal dysplasia characterized by craniofacial anomalies (absent eyelids, nose and ear anomalies, macrostomia), other ectodermal anomalies (skin and hair), and variable anomalies of the nipples, genitalia, and hands. This syndrome has poor growth. Mildly delayed language and gross motor skills are possible, but most patients are mentally normal.

Incidence

AMS is an extremely rare congenital abnormality with fewer than 20 cases described.

Genetic inheritance

Autosomal dominant inheritance caused by TWIST2-mutations on chromosome 2q37.3. TWIST2 encodes a transcription factor involved in the regulation of mesenchymal tissue development. Lysine instead of glutamate at TWIST2 residue 75 results in AMS (whereas glutamine or alanine in the same location leads to ☞Barber-Say Syndrome [BSS]).

Diagnosis

The diagnosis is made based on the clinical findings in the newborn.

Clinical aspects

The disorder is characterized by severe vertical shortening or absence of the eyelids (ablepharon/microblepharon), and often involves the eyebrows and the eyelashes. Other ocular findings include hypertelorism, corneal opacifications (possibly related to exposure keratopathy), nystagmus, and cryptophthalmos. An association with absent or hypoplastic zygomatic arches has been described. Microtia is common, while hearing loss and low-set ears are less frequent. The nose is often small with a depressed nasal bridge, hypoplastic alae nasi, and anteverted nostrils. Micrognathia has been described. Fusion defects of the lips result in macrostomia with a fish-like mouth. Obstructive sleep apnea syndrome has been reported in BSS, so it might also affect AMS patients. The nipples may be absent, hypoplastic or inverted. Genital findings include ambiguous genitalia, hypoplastic labia majora or micropenis. The skin appears thin, dry, and wrinkled (redundant skin folds). Scalp hair is either sparse or absent, and lanugo is absent in most patients. Omphalocele or ventral hernia has been described in some patients. Intellectual development is occasionally characterized by mildly delayed language and gross motor skills, but most patients are mentally normal. Poor growth is common as are short metacarpalia and syn- and camptodactyly of the fingers. AMS and BSS have many similarities and overlapping features. However, micro- or ablepharon, sparse, thin hair and total absence of lanugo are more characteristic for AMS, while hypertrichosis and ectropion are typical for BSS. The primary goal of surgical treatment is to preserve the cornea by early postnatal treatment with tarsorrhaphy, lid reconstruction with skin grafting, and the use of eye lubricants. Corrective craniofacial surgeries will mainly be performed at an age when craniofacial growth is completed.

Precautions before anesthesia

Venous access may be difficult due to the laxity and redundancy of the skin. Because of the facial anomalies (retrognathia/micrognathia and high-arched, narrow palate), difficult airway management should be anticipated. Anticholinergic premedication may be beneficial if difficult airway management is expected.

Anesthetic considerations