Ablepharon-Macrostomia Syndrome (AMS) is an extremely rare inherited disorder characterized by various physical abnormalities affecting the head and facial (craniofacial) area, the skin, the fingers, and the genitals. In addition, affected individuals may have malformations of the nipples and the abdominal wall. Infants and children with AMS may also experience delays in language development and, in some cases, mental retardation.
In infants with Ablepharon-Macrostomia Syndrome, characteristic craniofacial features may include absence or severe underdevelopment of the upper and lower eyelids (ablepharon or microblepharon) as well as absence of eyelashes and eyebrows; an unusually wide, "fish-like" mouth (macrostomia); and/or incompletely developed (rudimentary), low-set ears (pinnae). Abnormalities of the eyes may occur due to, or in association with, ablepharon or microblepharon. Individuals with AMS may also have additional characteristic features including abnormally sparse, thin hair; thin, wrinkled skin with excess (redundant) folds; webbed fingers with limited extension; and/or malformations of the external genitals. In some cases, additional features associated with AMS may include absent or abnormally small (hypoplastic) nipples and/or abdominal wall abnormalities. Although the exact cause of Ablepharon-Macrostomia Syndrome is not fully understood, some cases suggest that the disorder may be inherited as an autosomal recessive genetic trait.
Ablepharon-Macrostomia Syndrome (AMS), an extremely rare inherited disorder, is characterized by distinctive malformations affecting the head and facial (craniofacial) area; abnormalities of the skin, the fingers, and/or the genitals; additional physical abnormalities; delayed language developmen, and/or, in some cases, mental retardation.
In infants with AMS, distinctive craniofacial features may include absence or severe underdevelopment of the upper and lower eyelids (ablepharon or microblepharon). There is confusion in the medical literature concerning whether the eyelid abnormality in AMS represents true absence of eyelid formation (ablepharon), or whether affected infants may in fact have severely underdeveloped, rudimentary (vestigial) eyelid structures (microblepharon). Affected infants also demonstrate absence of the upper and lower eyelashes as well as the eyebrows.
Affected infants may have additional, characteristic craniofacial features. For example, infants with AMS may have an unusually wide, “fish-like” mouth (macrostomia) and resulting, defective fusion of the upper and lower lips on either side of the mouth. In addition, in some cases, the zygomatic arches of the skull may be absent. Zygomotic arches are the two bony arches spanning from the lower portion of the orbits of the eyes, across the prominence of the cheekbones to the bones forming part of the lower skull. Additional, distinctive craniofacial abnormalities associated with Ablepharon-Macrostomia Syndrome may include a triangularly-shaped face; a small nose; partial absence of tissue (coloboma) from the mid-portion of the nostril walls (alae), causing the nostrils to appear triangular; and/or incompletely developed (rudimentary), low-set ears (pinnae).
Individuals with AMS may experience abnormalities of the eyes due to, or in association with, ablepharon or microblepharon. For example, absence or severe underdevelopment of the eyelids may result in irritation and/or abnormal dryness of the cornea, the clear portion of the eye through which light passes. In some cases, individuals with Ablepharon-Macrostomia Syndrome may exhibit additional eye abnormalities including clouding (opacities) of the cornea that may improve with time in some cases; an unequal, inward deviation of the eyes (internal strabismus or esotropia); repeated involuntary eye movements (nystagmus); and/or complete or partial separation of the retina, the nerve-rich membrane lining the inner layer of the back of the eye, from membranes (choroids) in the outer layer (detached retina).
Infants with Ablepharon-Macrostomia Syndrome may lack the soft, downy hair that typically covers most areas of the body (lanugo). Affected individuals may also have unusually thin, sparse hair that develops abnormally late. In addition, individuals with AMS have unusually thin, wrinkled skin with excess (redundant) folds, particularly over the neck, hands, buttocks, backs of the knees (popliteal fossae), and/or feet.
In individuals with AMS, although the skin over the hands may be abnormally loose, the fingers may be permanently flexed due to tight skin over the finger joints. In addition, affected individuals may have partial webbing or fusion between the fingers (syndactyly) or the fingers may be flexed (camptodactyly). Due to such abnormalities, the fingers may have a limited range of movements. Hearing reduction and grow impairment may also occur.
In addition, infants and children with Ablepharon-Macrostomia Syndrome may exhibit genital malformations such as external genitals that are not distinctly male or female (ambiguous genitalia); an underdeveloped, unusually small penis (micropenis) that is improperly positioned (i.e., posteriorly displaced); undescended testicles (cryptorchidism); and/or absence of the skin pouch that normally contains the testes (scrotum). In addition, the nipples may be abnormally small (hypoplastic) or absent. Affected individuals may also exhibit protrusion of portions of the large intestine through an abnormal opening in the abdominal wall (abdominal or ventral hernia).
Children with Ablepharon-Macrostomia Syndrome may experience delayed language development. In addition, although some affected children may demonstrate mild mental retardation, others may have normal intelligence.
The exact underlying cause of Ablepharon-Macrostomia Syndrome is not known. According to investigators, some cases suggest that the disorder may be transmitted as an autosomal recessive trait. However, one affected family (kindred) has also been reported in which the disorder appeared to be transmitted as an autosomal dominant trait with variable expression.
Human traits, including the classic genetic diseases, are the product of the interaction of two genes, one received from the father and one from the mother.
In recessive disorders, the condition does not appear unless a person inherits the same defective gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease but usually will not show symptoms. The risk of transmitting the disease to the children of a couple, both of whom are carriers for a recessive disorder, is 25 percent. Fifty percent of their children risk being carriers of the disease but generally will not show symptoms of the disorder. Twenty-five percent of their children may receive both normal genes, one from each parent, and will be genetically normal (for that particular trait). The risk is the same for each pregnancy.
In autosomal dominant disorders, a single copy of the disease gene (received from either the mother or father) will be expressed “dominating” the other normal gene and resulting in the appearance of the disease. The risk of transmitting the disorder from affected parent to offspring is 50 percent for each pregnancy regardless of the sex of the resulting child. The risk is the same for each pregnancy. In autosomal dominant disorders with variable expression, the characteristics that are manifested may vary greatly in range and severity from case to case.
Further research is necessary to determine the underlying genetic cause or causes of Ablepharon-Macrostomia Syndrome.
Ablepharon-Macrostomia Syndrome (AMS) is an extremely rare genetic disorder that is apparent at birth (congenital). The disorder was originally described in 1977 (McCarthy GT) in two unrelated male children. A few additional isolated cases have since been recorded in the medical literature. In addition, investigators have described familial AMS in the sister of a previously reported affected female whose father has more minor features of the syndrome.
Ablepharon-Macrostomia Syndrome may be diagnosed at birth based upon a thorough clinical evaluation, identification of characteristic physical findings, and/or specialized imaging techniques. For example, in some cases, computerized tomography (CT) scanning may be helpful in demonstrating absence of the zygomatic arch, improper union of portions of the upper and lower jawbones (maxillary and mandibular prominences), etc. During CT scanning, a computer and x-rays are used to create a film showing cross-sectional images of tissue structure. Thorough examination and specialized testing may be conducted by eye specialists (ophthalmologists) to appropriately characterize eyelid malformations (ablepharon or microblepharon), detect any additional or associated eye abnormalities, and ensure appropriate preventive steps and/or prompt treatment.
The treatment of Ablepharon-Macrostomia Syndrome is directed toward the specific symptoms that are apparent in each individual. Treatment may require the coordinated efforts of a team of specialists who work together, to systematically and comprehensively plan an affected child's treatment. Such specialists may include pediatricians; ophthalmologists; specialists who diagnose and treat disorders of the skin (dermatologists), the male and female urinary tracts and the male genital tract (urologists), and the gastrointestinal tract (gastroenterologists); plastic and/or reconstructive surgeons, physical and occupational therapists, and/or other health care professionals.
Specific therapies for the treatment of AMS are symptomatic and supportive. For example, prior to more extensive therapy, appropriate lubricants (e.g., eyedrops) and/or other supportive techniques may be used to help prevent, correct, or ease eye irritation and dryness. In some cases, plastic and reconstructive surgery may possibly be performed to correct certain malformations such as abnormalities of the eyelids, mouth, and/or ears.
In some cases, surgery may also be performed to correct other eye abnormalities, malformations of the fingers, certain skin abnormalities, malformations of external genitalia, and/or ventral hernias. Other treatment is symptomatic and supportive. Genetic counseling will be of benefit for affected individuals and their families.
Research on genetic disorders and their causes is ongoing. The National Institutes of Health (NIH) is sponsoring the Human Genome Project which is aimed at mapping every gene in the human body and learning why they sometimes malfunction. It is hoped that this new knowledge will lead to prevention and treatment of genetic and familial disorders in the future.
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