Antley–Bixler syndrome is a rare, severe

autosomal An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosomal (sex chromosome) pairs, which may have different structures. The DNA in autosom ...

recessive In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and t ...

congenital disorder A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities ca ...

characterized by malformations and deformities affecting the majority of the skeleton and other areas of the body.

Presentation

Antley–Bixler syndrome presents itself at birth or

prenatal Prenatal development () includes the development of the embryo and of the fetus during a viviparous animal's gestation. Prenatal development starts with fertilization, in the germinal stage of embryonic development, and continues in fetal devel ...

ly. Features of the disorder include

brachycephaly Brachycephaly (derived from the Ancient Greek '' βραχύς'', 'short' and '' κεφαλή'', 'head') is the shape of a skull shorter than typical for its species. It is perceived as a desirable trait in some domesticated dog and cat breeds, ...

(flat forehead), craniosynostosis (complete skull-joint closure) of both coronal and

lambdoid suture The lambdoid suture (or lambdoidal suture) is a dense, fibrous connective tissue joint on the posterior aspect of the skull that connects the parietal bones with the occipital bone. It is continuous with the occipitomastoid suture. Structure T ...

s, facial hypoplasia (underdevelopment); bowed

ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...

(forearm bone) and

femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates wit ...

(thigh bone),

synostosis Synostosis (plural: synostoses) is fusion of two or more bones. It can be normal in puberty, fusion of the epiphyseal plate to become the epiphyseal line, or abnormal. When synostosis is abnormal it is a type of dysostosis. Examples of synostoses ...

of the

radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...

(forearm bone), humerus (upper arm bone) and

trapezoid A quadrilateral with at least one pair of parallel sides is called a trapezoid () in American and Canadian English. In British and other forms of English, it is called a trapezium (). A trapezoid is necessarily a convex quadrilateral in Eu ...

(hand bone);

camptodactyly Camptodactyly is a medical condition that causes one or more fingers or toes to be permanently bent. It involves fixed flexion deformity of the proximal interphalangeal joints. Camptodactyly can be caused by a genetic disorder. In that case, it ...

(fused interphalangeal joints in the fingers), thin ilial wings (outer pelvic plate) and

renal The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; bloo ...

malformations. Other symptoms, such as

cardiac The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide to t ...

malformations, proptotic exophthalmos (bulging eyes),

arachnodactyly Arachnodactyly ("spider fingers") is a medical condition that is characterized by fingers and toes that are abnormally long and slender, in comparison to the palm of the hand and arch of the foot. In some cases, the thumbs of an individual with the ...

(spider-like fingers) as well as nasal,

anal Anal may refer to: Related to the anus *Related to the anus of animals: ** Anal fin, in fish anatomy ** Anal vein, in insect anatomy ** Anal scale, in reptile anatomy *Related to the human anus: ** Anal sex, a type of sexual activity involving s ...

and

vaginal atresia Vaginal atresia is a condition in which the vagina is abnormally closed or absent. The main causes can either be complete vaginal hypoplasia, or a vaginal obstruction, often caused by an imperforate hymen or, less commonly, a transverse vaginal se ...

(occlusion) have been reported.

Pathophysiology

There are two distinct

gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...

tic

mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA replication, DNA or viral repl ...

s associated with the Antley–Bixler syndrome

phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological pr ...

, which suggests the disorder may be genetically heterogeneous. Antley–Bixler syndrome is inherited in an autosomal recessive pattern, which means the defective gene is located on an autosome, and two copies of the gene (one inherited from each parent) are required to be born with the disorder. The parents of an individual with an autosomal recessive disorder both carry one copy of the defective gene but are usually not affected by the disorder.

Diagnosis

The diagnosis of Antley–Bixler syndrome is usually made after birth (postnatally) based upon a thorough clinical evaluation and characteristic physical findings. Other imaging procedures and genetic testing may also be conducted to diagnose the disorder. In some children, a diagnosis of Antley–Bixler syndrome may be suggested before birth (prenatally) based upon tests such as ultrasound. Ultrasound allows us to generate an image of the developing fetus, which may then reveal characteristic findings that are associated with the disorder. If there is a known family history of the condition, targeted genetic testing is available for patient families.

Treatment

The treatment of Antley–Bixler syndrome is directed toward the specific symptoms that are seen in each individual. Such treatment requires the coordinated efforts of a team of medical professionals who may need to systematically and comprehensively plan the treatment for a child with this condition. These professionals may include pediatricians, surgeons, physicians who specialize in disorders of specific body areas and organs. In individuals with Antley–Bixler syndrome, treatment typically includes surgery. The surgical procedures performed will depend upon the severity of the skeletal problems and its associated symptoms. It is possible that multiple surgeries will be needed in order to treat the malformations present. There is no cure for the condition. All treatment is supportive and aimed at managing symptoms. However, early intervention may be important in ensuring that affected children reach their potential. For example, physical therapy is typically recommended to help improve the range of movement at certain joint contractures. Other therapies that may aide in managing symptoms include occupational therapy and speech therapy. Because this is a genetic condition, individuals with Antley–Bixler syndrome and their families would benefit from meeting with a genetic counselor. Genetic counselors are professionals who have specialized education in genetics and counseling to provide personalized help patients may need as they make decisions about their genetic health.

Eponym

Antley–Bixler syndrome is named after Drs. Ray M. Antley (1937–2014) and David Bixler (1929–2005), who first described the disorder in a journal report from 1975.

References

:11. https://rarediseases.org/rare-diseases/antley-bixler-syndrome/

External links

{{DEFAULTSORT:Antley-Bixler syndrome Cell surface receptor deficiencies Autosomal recessive disorders Rare diseases Syndromes affecting the heart Cholesterol and steroid metabolism disorders Syndromes affecting the eye Syndromes with craniofacial abnormalities