Amniocentesis is a medical procedure used primarily in the prenatal diagnosis of genetic conditions. It has other uses such as in the assessment of infection and fetal lung maturity. Prenatal diagnostic testing, which includes amniocentesis, is necessary to conclusively diagnose the majority of genetic disorders, with amniocentesis being the gold-standard procedure after 15 weeks' gestation.
Anencephaly is the absence of a major portion of the brain, skull, and scalp that occurs during embryonic development. It is a cephalic disorder that results from a neural tube defect that occurs when the rostral (head) end of the neural tube fails to close, usually between the 23rd and 26th day following conception. Strictly speaking, the Greek term translates as "without a brain", but it is accepted that children born with this disorder usually only lack a telencephalon, the largest part of the brain consisting mainly of the cerebral hemispheres, including the neocortex, which is responsible for cognition. The remaining structure is usually covered only by a thin layer of membrane—skin, bone, meninges, etc., are all lacking. With very few exceptions, infants with this disorder do not survive longer than a few hours or days after birth.
Holoprosencephaly (HPE) is a cephalic disorder in which the prosencephalon fails to develop into two hemispheres, typically occurring between the 18th and 28th day of gestation. Normally, the forebrain is formed and the face begins to develop in the fifth and sixth weeks of human pregnancy. The condition also occurs in other species.
Iniencephaly is a rare type of cephalic disorder characterised by three common characteristics: a defect to the occipital bone, spina bifida of the cervical vertebrae and retroflexion of the head on the cervical spine. Stillbirth is the most common outcome, with a few rare examples of live birth, after which death invariably occurs within a short time.
Crouzon syndrome is an autosomal dominant genetic disorder known as a branchial arch syndrome. Specifically, this syndrome affects the first branchial arch, which is the precursor of the maxilla and mandible. Since the branchial arches are important developmental features in a growing embryo, disturbances in their development create lasting and widespread effects.
Smith–Lemli–Opitz syndrome is an inborn error of cholesterol synthesis. It is an autosomal recessive, multiple malformation syndrome caused by a mutation in the enzyme 7-Dehydrocholesterol reductase encoded by the DHCR7 gene. It causes a broad spectrum of effects, ranging from mild intellectual disability and behavioural problems to lethal malformations.
Saethre–Chotzen syndrome (SCS), also known as acrocephalosyndactyly type III, is a rare congenital disorder associated with craniosynostosis. This affects the shape of the head and face, resulting in a cone-shaped head and an asymmetrical face. Individuals with SCS also have droopy eyelids (ptosis), widely spaced eyes (hypertelorism), and minor abnormalities of the hands and feet (syndactyly). Individuals with more severe cases of SCS may have mild to moderate intellectual or learning disabilities. Depending on the level of severity, some individuals with SCS may require some form of medical or surgical intervention. Most individuals with SCS live fairly normal lives, regardless of whether medical treatment is needed or not.
Acalvaria is a rare malformation consisting of the absence of the calvarial bones, dura mater and associated muscles in the presence of a normal skull base and normal facial bones. The central nervous system is usually unaffected. The presumed pathogenesis of acalvaria is the faulty migration of the membranous neurocranium with normal placement of the embryonic ectoderm, resulting in the absence of the calvaria, but with an intact layer of skin over the brain parenchyma. In other words, instead of having a skull cap protecting the brain, there is only skin covering it. The size of the area that is missing the skull cap can vary from case to case. In extreme cases, the entire top part of the cranium that is dome-shaped may be absent.
Simpson–Golabi–Behmel syndrome (SGBS), is a rare inherited congenital disorder that can cause craniofacial, skeletal, vascular, cardiac, and renal abnormalities. There is a high prevalence of cancer associated in those with sgbs which includes wilms tumors, neuroblastoma, tumors of the adrenal gland, liver, lungs and abdominal organs. The syndrome is inherited in an X-linked recessive manner. Females that possess one copy of the mutation are considered to be carriers of the syndrome but may still express varying degrees of the phenotype, suffering mild to severe malady. Males experience a higher likelihood of fetal death.
Acrocephalosyndactyly is a group of autosomal dominant congenital disorders characterized by craniofacial (craniosynostosis) and hand and foot (syndactyly) abnormalities. When polydactyly is present, the classification is acrocephalopolysyndactyly. Acrocephalosyndactyly is mainly diagnosed postnatally, although prenatal diagnosis is possible if the mutation is known to be within the family genome. Treatment often involves surgery in early childhood to correct for craniosynostosis and syndactyly.
Campomelic dysplasia (CMD) is a genetic disorder characterized by bowing of the long bones and many other skeletal and extraskeletal features. It can be lethal in the neonatal period due to respiratory insufficiency, but the severity of the disease is variable, and a significant proportion of patients survive into adulthood. The name is derived from the Greek roots campo, meaning bent, and melia, meaning limb. An unusual aspect of the disease is that up to two-thirds of affected 46,XY genotypic males display a range of disorders of sexual development (DSD) and genital ambiguities or may even develop as normal phenotypic females as in complete 46 XY sex reversal. An atypical form of the disease with absence of bowed limbs is called, prosaically, acampomelic campomelic dysplasia (ACD) and is found in about 10% of patients, particularly those surviving the neonatal period.
Muenke syndrome, also known as FGFR3-related craniosynostosis, is a human specific condition characterized by the premature closure of certain bones of the skull during development, which affects the shape of the head and face. First described by Maximilian Muenke, the syndrome occurs in about 1 in 30,000 newborns. This condition accounts for an estimated 8 percent of all cases of craniosynostosis.
3C syndrome is a rare condition whose symptoms include heart defects, cerebellar hypoplasia, and cranial dysmorphism. It was first described in the medical literature in 1987 by Ritscher and Schinzel, for whom the disorder is sometimes named.
Frontonasal dysplasia (FND) is a congenital malformation of the midface. For the diagnosis of FND, a patient should present at least two of the following characteristics: hypertelorism, a wide nasal root, vertical midline cleft of the nose and/or upper lip, cleft of the wings of the nose, malformed nasal tip, encephalocele or V-shaped hair pattern on the forehead. The cause of FND remains unknown. FND seems to be sporadic (random) and multiple environmental factors are suggested as possible causes for the syndrome. However, in some families multiple cases of FND were reported, which suggests a genetic cause of FND.
3-M syndrome or 3M3 is a rare hereditary disorder characterized by severe growth retardation, facial dysmorphia, and skeletal abnormalities. The name 3-M is derived from the initials of the three researchers who first identified it: Miller, McKusick, and Malvaux and report their findings in the medical literature in 1972. Mutations in any one of the following three genes: CUL7, OBSL1, and CCDC8 are responsible for the occurrence of this disorder. It is inherited through an autosomal recessive pattern and considered very rare, so far less than 100 cases worldwide have been identified. Diagnosis is based on the presence of clinical features. Genetic testing can confirm the diagnosis and identify the specific gene involved. Treatment is aimed at addressing the growth and skeletal problems and may include surgical bone lengthening, adaptive aids, and physical therapy. An endocrinologist may assist with growth hormone replacement and appropriate evaluations during puberty.
Nervous system diseases, also known as nervous system or neurological disorders, refers to a small class of medical conditions affecting the nervous system. This category encompasses over 600 different conditions, including genetic disorders, infections, cancer, seizure disorders, conditions with a cardiovascular origin, congenital and developmental disorders, and degenerative disorders.
Rachischisis is a developmental birth defect involving the neural tube. This anomaly occurs in utero, when the posterior neuropore of the neural tube fails to close by the 27th intrauterine day. As a consequence the vertebrae overlying the open portion of the spinal cord do not fully form and remain unfused and open, leaving the spinal cord exposed. Patients with rachischisis have motor and sensory deficits, chronic infections, and disturbances in bladder function. This defect often occurs with anencephaly.
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.
XK aprosencephaly is an extremely rare congenital disorder characterized by the absence of the embryonic forebrain. Because the prosencephalon gives way to the cerebral cortex, survival with aprosencephaly is not possible outside utero. The external symptoms are similar to holoprosencephaly, a related disorder, including a smaller than normal head (microcephaly), small eyeballs (microphthalmia), a small mouth (microstomia), anal atresia, and abnormalities of the external genitalia, radius, nostrils, and pharynx (throat).
Dysosteosclerosis (DSS), also known as autosomal recessive dysosteosclerosis or X-linked recessive dysosteosclerosis, is a rare osteoclast-poor form of osteosclerosis that is presented during infancy and early childhood, characterized by progressive osteosclerosis and platyspondyly. Platyspondyly and other skeletal abnormalities are radiographic features of the disease which distinguish DSS from other osteosclerotic disorders. Patients usually experience neurological and psychological deterioration, therefore patients are commonly associated with delayed milestones.
