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 autosome ...

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 ...

congenital disorder A birth defect is an abnormal condition that is present at childbirth, birth, regardless of its cause. Birth defects may result in disability, disabilities that may be physical disability, physical, intellectual disability, intellectual, or dev ...

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 () involves the embryonic development, development of the embryo and of the fetus during a viviparity, viviparous animal's gestation. Prenatal development starts with fertilization, in the germinal stage of embryonic develop ...

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 average in its species. It is perceived as a cosmetically desirable trait in some domesticated dog and ...

(flat forehead),

craniosynostosis Craniosynostosis is a condition in which one or more of the fibrous sutures in a young infant's skull prematurely fuses by turning into bone (ossification), thereby changing the growth pattern of the skull. Because the skull cannot expand perpe ...

(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 Hypoplasia (; adjective form ''hypoplastic'') is underdevelopment or incomplete development of a tissue or organ.ulna The ulna or ulnar bone (: ulnae or ulnas) is a long bone in the forearm stretching from the elbow to the wrist. It is on the same side of the forearm as the little finger, running parallel to the Radius (bone), radius, the forearm's other long ...

(forearm bone) and

femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...

(thigh bone),

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

of the

radius In classical geometry, a radius (: radii or radiuses) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The radius of a regular polygon is th ...

(forearm bone),

humerus The humerus (; : humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius (bone), radius and ulna, and consists of three sections. The humeral upper extrem ...

(upper arm bone) and

trapezoid In geometry, a trapezoid () in North American English, or trapezium () in British English, is a quadrilateral that has at least one pair of parallel sides. The parallel sides are called the ''bases'' of the trapezoid. The other two sides are ...

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

renal In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and right in the retrop ...

malformations. Other symptoms, such as

cardiac The heart is a muscular organ found in humans and other animals. This organ pumps blood through the blood vessels. The heart and blood vessels together make the circulatory system. The pumped blood carries oxygen and nutrients to the tissu ...

malformations, proptotic exophthalmos (bulging eyes), arachnodactyly (spider-like fingers) as well as

nasal Nasal is an adjective referring to the nose, part of human or animal anatomy. It may also be shorthand for the following uses in combination: * With reference to the human nose: ** Nasal administration, a method of pharmaceutical drug delivery * ...

, anal and vaginal atresia (occlusion) have been reported.

Pathophysiology

There are two distinct

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

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 or viral replication, ...

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 (physical form and structure), its developmental processes, its biochemical and physiological propert ...

, which suggests the disorder may be genetically heterogeneous. Antley–Bixler syndrome is inherited in an

autosomal recessive In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the Phenotype, effect of a different variant of the same gene on Homologous chromosome, the other copy of the chromosome. The firs ...

pattern, which means the defective gene is located on an

autosome 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 autosomes ...

, 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 Genetic testing, also known as DNA testing, is used to identify changes in DNA sequence or chromosome structure. Genetic testing can also include measuring the results of genetic changes, such as RNA analysis as an output of gene expression, or ...

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