A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosome abnormality. Although polygenic disorders are the most common, the term is mostly used when discussing disorders with a single genetic cause, either in a gene or chromosome. The mutation responsible can occur spontaneously before embryonic development, or it can be inherited from two parents who are carriers of a faulty gene or from a parent with the disorder. When the genetic disorder is inherited from one or both parents, it is also classified as a hereditary disease. Some disorders are caused by a mutation on the X chromosome and have X-linked inheritance. Very few disorders are inherited on the Y chromosome or mitochondrial DNA.
Arachnodactyly 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 condition are pulled inwards towards the palm. This condition is present at birth.
Apert syndrome is a form of acrocephalosyndactyly, a congenital disorder characterized by malformations of the skull, face, hands and feet. It is classified as a branchial arch syndrome, affecting the first branchial arch, the precursor of the maxilla and mandible. Disturbances in the development of the branchial arches in fetal development create lasting and widespread effects.
Haploinsufficiency in genetics describes a model of dominant gene action in diploid organisms, in which a single copy of the wild-type allele at a locus in heterozygous combination with a variant allele is insufficient to produce the wild-type phenotype. Haploinsufficiency may arise from a de novo or inherited loss-of-function mutation in the variant allele, such that it yields little or no gene product. Although the other, standard allele still produces the standard amount of product, the total product is insufficient to produce the standard phenotype. This heterozygous genotype may result in a non- or sub-standard, deleterious, and (or) disease phenotype. Haploinsufficiency is the standard explanation for dominant deleterious alleles.
Van der Woude syndrome (VDWS) is a genetic disorder characterized by the combination of lower lip pits, cleft lip with or without cleft palate (CL/P), and cleft palate only (CPO). The frequency of orofacial clefts ranges from 1:1000 to 1:500 births worldwide, and there are more than 400 syndromes that involve CL/P. VWS is distinct from other clefting syndromes due to the combination of cleft lip and palate (CLP) and CPO within the same family. Other features frequently associated with VWS include hypodontia in 10-81% of cases, narrow arched palate, congenital heart disease, heart murmur and cerebral abnormalities, syndactyly of the hands, polythelia, ankyloglossia, and adhesions between the upper and lower gum pads.
Barakat syndrome is a rare disease characterized by hypoparathyroidism, sensorineural deafness and renal disease, and hence also known as HDR syndrome. It is an autosomal dominant condition with incomplete penetrance and variable expressivity that was first described by Amin J. Barakat et al. in 1977.
Loeys–Dietz syndrome (LDS) is an autosomal dominant genetic connective tissue disorder. It has features similar to Marfan syndrome and Ehlers–Danlos syndrome. The disorder is marked by aneurysms in the aorta, often in children, and the aorta may also undergo sudden dissection in the weakened layers of the wall of the aorta. Aneurysms and dissections also can occur in arteries other than the aorta. Because aneurysms in children tend to rupture early, children are at greater risk for dying if the syndrome is not identified. Surgery to repair aortic aneurysms is essential for treatment.
1p36 deletion syndrome is a congenital genetic disorder characterized by moderate to severe intellectual disability, delayed growth, hypotonia, seizures, limited speech ability, malformations, hearing and vision impairment, and distinct facial features. The symptoms may vary, depending on the exact location of the chromosomal deletion.
Congenital contractural arachnodactyly (CCA), also known as Beals–Hecht syndrome, is a rare autosomal dominant congenital connective tissue disorder. As with Marfan syndrome, people with CCA typically have an arm span that is greater than their height and very long fingers and toes. However, Beals and Hecht discovered in 1972 that, unlike Marfan's, CCA is caused by mutations to the fibrillin-2 (FBN2) gene rather than the fibrillin-1 (FBN1) gene.
Young–Simpson syndrome (YSS) is a rare congenital disorder with symptoms including hypothyroidism, heart defects, facial dysmorphism, cryptorchidism in males, hypotonia, intellectual disability, and postnatal growth retardation.
Clinodactyly is a medical term describing the curvature of a digit in the plane of the palm, most commonly the fifth finger towards the adjacent fourth finger.
Lujan–Fryns syndrome (LFS) is an X-linked genetic disorder that causes mild to moderate intellectual disability and features described as Marfanoid habitus, referring to a group of physical characteristics similar to those found in Marfan syndrome. These features include a tall, thin stature and long, slender limbs. LFS is also associated with psychopathology and behavioral abnormalities, and it exhibits a number of malformations affecting the brain and heart. The disorder is inherited in an X-linked dominant manner, and is attributed to a missense mutation in the MED12 gene. There is currently no treatment or therapy for the underlying MED12 malfunction, and the exact cause of the disorder remains unclear.
Fryns syndrome is an autosomal recessive multiple congenital anomaly syndrome that is usually lethal in the neonatal period. Fryns (1987) reviewed the syndrome.
Roberts syndrome, or sometimes called pseudothalidomide syndrome, is an extremely rare autosomal recessive genetic disorder that is characterized by mild to severe prenatal retardation or disruption of cell division, leading to malformation of the bones in the skull, face, arms, and legs.
Hand-foot-genital syndrome (HFGS) is characterized by limb malformations and urogenital defects. Mild bilateral shortening of the thumbs and great toes, caused primarily by shortening of the distal phalanx and/or the first metacarpal or metatarsal, is the most common limb malformation and results in impaired dexterity or apposition of the thumbs. Urogenital abnormalities include abnormalities of the ureters and urethra and various degrees of incomplete Müllerian fusion in females and hypospadias of variable severity with or without chordee in males. Vesicoureteral reflux, recurrent urinary tract infections, and chronic pyelonephritis are common; fertility is normal.
Liebenberg syndrome is a rare autosomal genetic disease that involves a deletion mutation upstream of the PITX1 gene, which is one that's responsible for the body's organization, specifically in forming lower limbs. In animal studies, when this deletion was introduced to developing birds, their wing buds were noted to take on limb-like structures.
Sanjad–Sakati syndrome is a rare autosomal recessive genetic condition seen in offspring of Middle Eastern origin. It was first described in Saudi Arabia, but has been seen in Qatari, Kuwaiti, Omani and other children from the Middle East as well as elsewhere. The condition is caused by mutations or deletions in the TBCE gene of Chromosome No.1.
Fryns-Aftimos syndrome is a rare chromosomal condition and is associated with pachygyria, severe mental retardation, epilepsy and characteristic facial features. This syndrome is a malformation syndrome, characterized by numerous facial dysmorphias not limited to hypertelorism, iris or retinal coloboma, cleft lip, and congenital heart defects. This syndrome has been seen in 30 unrelated people. Characterized by a de novo mutation located on chromosome 7p22, there is typically no family history prior to onset. The severity of the disorder can be determined by the size of the deletion on 7p22, enveloping the ACTB gene and surrounding genes, which is consistent with a contiguous gene deletion syndrome. Confirming a diagnosis of Fryns-Aftimos syndrome typically consists of serial single-gene testing or multigene panel of genes of interest or exome sequencing.
Kirner's deformity, also known as dystelephangy, is an uncommon genetic hand malformation which is characterized by a radial and volar curvature of the distal phalange of the fifth (pinky) finger. It is merely cosmetic and doesn't affect hand function.
Heart-hand syndrome, Slovenian type is a rare autosomal dominant genetic disorder belonging to the heart-hand syndromes.
