Hypotonia is a common finding. Around 10% of people with distal 18q- have seizures.

Dysmyelination is a common finding in people with distal 18q-, present in about 95%. Hypoplasia of the corpus callosum is also a common finding.

Robinow noted the resemblance of affected patients' faces to that of a fetus, using the term "fetal facies" to describe the appearance of a small face and widely spaced eyes. Clinical features also may include a short, upturned nose, a prominent forehead, and a flat nasal bridge. The upper lip may be "tented", exposing dental crowding, "tongue tie", or gum hypertrophy.

Though the eyes do not protrude, abnormalities in the lower eyelid may give that impression. Surgery may be necessary if the eyes cannot close fully. In addition, the ears may be set low on the head or have a deformed pinna.

Patients suffer from dwarfism, short lower arms, small feet, and small hands. Fingers and toes may also be abnormally short and laterally or medially bent. The thumb may be displaced and some patients, notably in Turkey, experience ectrodactyly. All patients often suffer from vertebral segmentation abnormalities. Those with the dominant variant have, at most, a single butterfly vertebra. Those with the recessive form, however, may suffer from hemivertebrae, vertebral fusion, and rib anomalies. Some cases resemble Jarcho-Levin syndrome or spondylocostal dysostosis.

Genital defects characteristically seen in males include a micropenis with a normally developed scrotum and testes. Sometimes, testicles may be undescended, or the patient may suffer from hypospadias. Female genital defects may include a reduced size clitoris and underdeveloped labia minora. Infrequently, the labia majora may also be underdeveloped. Some research has shown that females may experience vaginal atresia or haematocolpos.

The autosomal recessive form of the disorder tends to be much more severe. Examples of differences are summarized in the following table:

Signs and symptoms arising from liver damage in Alagille syndrome may include a yellowish tinge in the skin and the whites of the eyes (jaundice), itching (pruritus), pale stools (acholia), an enlarged liver (hepatomegaly), an enlarged spleen (splenomegaly) and deposits of cholesterol in the skin (xanthomas). A liver biopsy may indicate too few bile ducts (bile duct paucity) or, in some cases, the complete absence of bile ducts (biliary atresia). Bile duct paucity results in the reduced absorption of fat and vitamins (A, D, E and K), which may lead to rickets or a failure to thrive in children. Around 15% of patients will experience liver cirrhosis in the course of their disease. Hepatocellular cancer has been reported in a number of cases.

The severity of the disorder can vary within the same family, with symptoms ranging from so mild as to go unnoticed to severe heart and/or liver disease requiring transplantation. It is difficult to predict a given patient's prognosis, but there are a few known indicators of earlier death.

The diagnosis is based on the following clinical findings:

- microcephaly

- clinodactyly and shortness of index and little fingers

- syndactyly of 2nd & 3rd and 4th & 5th toe

- short palpebral fissures

- esophageal and/or duodenal atresia

Renal (kidney) defects are seen in approximately 50 percent of patients with VACTERL association. In addition, up to 35 percent of patients with VACTERL association have a single umbilical artery (there are usually two arteries and one vein) which is often associated with additional kidney or urologic problems. Renal abnormalities in VACTERL association can be severe, with incomplete formation of one or both kidneys or urologic abnormalities such as obstruction of outflow of urine from the kidneys or severe reflux (backflow) of urine into the kidneys from the bladder. These problems can cause kidney failure early in life and may require kidney transplant. Many of these problems can be corrected surgically before any damage can occur.

Robinow syndrome is an extremely rare genetic disorder characterized by short-limbed dwarfism, abnormalities in the head, face, and external genitalia, as well as vertebral segmentation. The disorder was first described in 1969 by human geneticist Meinhard Robinow, along with physicians Frederic N. Silverman and Hugo D. Smith, in the "American Journal of Diseases of Children". By 2002, over 100 cases had been documented and introduced into medical literature.

Two forms of the disorder exist, dominant and recessive, of which the former is more common. Patients with the dominant version often suffer moderately from the aforementioned symptoms. Recessive cases, on the other hand, are usually more physically marked, and individuals may exhibit more skeletal abnormalities. The recessive form is particularly frequent in Turkey. However, this can likely be explained by a common ancestor, as these patients' families can be traced to a single town in Eastern Turkey. Clusters of the autosomal recessive form have also been documented in Oman and Czechoslovakia.

The syndrome is also known as Robinow-Silverman-Smith syndrome, Robinow dwarfism, fetal face, fetal face syndrome, fetal facies syndrome, acral dysostosis with facial and genital abnormalities, or mesomelic dwarfism-small genitalia syndrome. The recessive form was previously known as Covesdem syndrome.

Esophageal atresia with tracheo-esophageal fistula (TE fistula) is seen in about 70 percent of patients with VACTERL association, although it can frequently occur as an isolated defect. Fifteen percent to 33 percent of patients with TE fistulas will also have congenital heart disease. However these babies usually have uncomplicated heart defects, like a ventricular septal defect, which may not require any surgery.

Clinically, McKusick–Kaufman syndrome is characterized by a combination of three features: postaxial polydactyly, heart defects, and genital abnormalities:

- Vaginal atresia with hydrometrocolpos

- Double vagina and/or uterus.

- Hypospadias, chordee (a downward-curving penis), and undescended testes (cryptorchidism).

- ureter stenosis or ureteric atresia

Usually associated with diaphragmatic hernia,

pulmonary hypoplasia,

imperforate anus,

micropenis,

bilateral cryptorchidism,

cerebral ventricular dilation,

camptodactyly,

agenesis of sacrum,

low-set ear.

- Fryns et al. (1979) reported 2 stillborn sisters with a multiple congenital anomaly syndrome characterized by coarse facies with cloudy corneae, diaphragmatic defects, absence of lung lobulation, and distal limb deformities. A sporadic case was reported by Goddeeris et al. (1980). Fitch (1988) claimed that she and her colleagues were the first to describe this disorder. In 1978 they reported a single infant, born of second-cousin parents, who had absent left hemidiaphragm, hydrocephalus, arhinencephaly, and cardiovascular anomalies.

- Lubinsky et al. (1983) reported a brother and sister with Fryns syndrome who both died in the neonatal period. Facial anomalies included broad nasal bridge, microretrognathia, abnormal helices, and cleft palate. Other features included distal digital hypoplasia, lung hypoplasia, and urogenital abnormalities, including shawl scrotum, uterus bicornis, and renal cysts. They were discordant for diaphragmatic hernia, cleft lip, and Dandy–Walker anomaly.

- Meinecke and Fryns (1985) reported an affected child; consanguinity of the parents supported recessive inheritance. They noted that a diaphragmatic defect had been described in 4 of the 5 reported cases and lung hypoplasia in all. Young et al. (1986) reported a sixth case. The male infant survived for 12 days. These authors listed corneal clouding, camptodactyly with hypoplastic nails, and abnormalities of the diaphragm as cardinal features.

- Samueloff et al. (1987) described a family in which all 4 children had Fryns syndrome and neonatal mortality. Features included hypoplastic lungs, cleft palate, retrognathia, micrognathism, small thorax, diaphragmatic hernia, distal limb hypoplasia, and early onset of polyhydramnios with premature delivery. Schwyzer et al. (1987) described an affected infant whose parents were second cousins.

- Moerman et al. (1988) described infant brother and sister with the syndrome of diaphragmatic hernia, abnormal face, and distal limb anomalies. Both died shortly after birth with severe respiratory distress. Ultrasonography demonstrated fetal hydrops, diaphragmatic hernia, and striking dilatation of the cerebral ventricles in both infants. Post-mortem examination showed Dandy–Walker malformation, ventricular septal defect, and renal cystic dysplasia.

- Cunniff et al. (1990) described affected brothers and 3 other cases, bringing the total reported cases of Fryns syndrome to 25. One of the affected brothers was still alive at the age of 24 months. Bilateral diaphragmatic hernias had been repaired on the first day of life. He required extracorporeal membrane oxygenation therapy for 5 days and oscillatory therapy for 3 months. Ventriculoperitoneal shunt was required because of slowly progressive hydrocephalus. Scoliosis was associated with extranumerary vertebral bodies and 13 ribs. Because of delayed gastric emptying, a gastrostomy tube was inserted. In addition, because of persistent chylothorax, he underwent decortication of the right lung and oversewing of the thoracic duct.

- Kershisnik et al. (1991) suggested that osteochondrodysplasia is a feature of Fryns syndrome.

- Willems et al. (1991) suggested that a diaphragmatic hernia is not a necessary feature of Fryns syndrome. They described a child with all the usual features except for diaphragmatic hernia; the diaphragm was reduced to a fibrous web with little muscular component. Bartsch et al. (1995) presented 2 unrelated cases with a typical picture of Fryns syndrome but without diaphragmatic hernia. One of these patients was alive at the age of 14 months, but was severely retarded. Bamforth et al. (1987) and Hanssen et al. (1992) also described patients with this syndrome who survived the neonatal period. In the report of Hanssen et al. (1992), 2 older sibs had died in utero. The reports suggested that survival beyond the neonatal period is possible when the diaphragmatic defect and lung hypoplasia are not present. However, mental retardation has been present in all surviving patients.

- Vargas et al. (2000) reported a pair of monozygotic twins with Fryns syndrome discordant for severity of diaphragmatic defect. Both twins had macrocephaly, coarse facial appearance, hypoplasia of distal phalanges, and an extra pair of ribs. Twin A lacked an apparent diaphragmatic defect, and at 1 year of age had mild developmental delay. Twin B had a left congenital diaphragmatic hernia and died neonatally. The authors suggested that absence of diaphragmatic defect in Fryns syndrome may represent a subpopulation of more mildly affected patients.

- Aymé, "et al." (1989) described 8 cases of Fryns syndrome in France. The most frequent anomalies were diaphragmatic defects, lung hypoplasia, cleft lip and palate, cardiac defects, including septal defects and aortic arch anomalies, renal cysts, urinary tract malformations, and distal limb hypoplasia. Most patients also had hypoplastic external genitalia and anomalies of internal genitalia, including bifid or hypoplastic uterus or immature testes. The digestive tract was also often abnormal; duodenal atresia, pyloric hyperplasia, malrotation and common mesentery were present in about half of the patients. When the brain was examined, more than half were found to have Dandy–Walker anomaly and/or agenesis of the corpus callosum. A few patients demonstrated cloudy cornea. Histologically, 2 of 3 patients showed retinal dysplasia with rosettes and gliosis of the retina, thickness of the posterior capsule of the lens, and irregularities of Bowman membrane.

- Alessandri et al. (2005) reported a newborn from the Comores Islands with clinical features of Fryns syndrome without diaphragmatic hernia. They noted that diaphragmatic hernia is found in more than 80% of cases and that at least 13 other cases had been reported with an intact diaphragm.

- In a postneonatal survivor of Fryns syndrome, Riela et al. (1995) described myoclonus appearing shortly after birth, which was well controlled on valproate. Progressive cerebral and brainstem atrophy was noted on serial MRIs made at 3 months and after 6 months of age.

- Van Hove et al. (1995) described a boy with Fryns syndrome who survived to age 3 years and reviewed the outcome of other reported survivors (approximately 14% of reported cases). Survivors tended to have less frequent diaphragmatic hernia, milder lung hypoplasia, absence of complex cardiac malformation, and severe neurologic impairment. Their patient had malformations of gyration and sulcation, particularly around the central sulcus, and hypoplastic optic tracts beyond the optic chiasm associated with profound mental retardation.

- Fryns and Moerman (1998) reported a second-trimester male fetus with Fryns syndrome and midline scalp defects. The authors stated that the finding of a scalp defect in Fryns syndrome confirms that it is a true malformation syndrome with major involvement of the midline structures.

- Ramsing et al. (2000) described 2 sibships with 4 fetuses and 1 preterm baby of 31 weeks' gestation affected by a multiple congenital disorder suggestive of Fryns syndrome. In addition to the diaphragmatic defects and distal limb anomalies, they presented with fetal hydrops, cystic hygroma, and multiple pterygias. Two affected fetuses in 1 family showed severe craniofacial abnormalities with bilateral cleft lip and palate and cardiovascular malformation.

- Arnold et al. (2003) reported a male fetus with Fryns syndrome and additional abnormalities, in particular, multiple midline developmental defects including gastroschisis, central nervous system defects with left arrhinencephaly and cerebellar hypoplasia, midline cleft of the upper lip, alveolar ridge, and maxillary bone, and cleft nose with bilateral choanal atresia.

- Pierson et al. (2004) reviewed 77 reported patients with Fryns syndrome and summarized the abnormal eye findings identified in 12 of them. They also described 3 new patients with Fryns syndrome, 1 of whom demonstrated unilateral microphthalmia and cloudy cornea.

- Slavotinek et al. (2005) noted that Fryns syndrome may be the most common autosomal recessive syndrome in which congenital diaphragmatic hernia (see DIH2, 222400) is a cardinal feature. The autosomal recessive inheritance in Fryns syndrome contrasts with the sporadic inheritance for most patients with DIH.

In this disorder lesions can occur anywhere from the stomach to the anus. The clinical presentation depends on the location of the lesions(s).

The failure of the metanephros to develop in cases of BRA and some cases involving unilateral renal agenesis (URA) is due primarily to the failure of the mesonephric duct to produce a ureteric bud capable of inducing the metanephric mesenchyme. The failed induction will thereby cause the subsequent degeneration of the metanephros by apoptosis and other mechanisms. The mesonephric duct(s) of the agenic kidney(s) will also degenerate and fail to connect with the bladder. Therefore, the means by which the fetus produces urine and transports it to the bladder for excretion into the amniotic sac has been severely compromised (in the cases of URA), or completely eliminated (in the cases of BRA). The decreased volume of amniotic fluid causes the growing fetus to become compressed by the mother's uterus. This compression can cause many physical deformities of the fetus, most common of which is Potter facies. Lower extremity anomalies are frequent in these cases, which often presents with clubbed feet and/or bowing of the legs. Sirenomelia, or "Mermaid syndrome" (which occurs approximately in 1:45,000 births) can also present. In fact, nearly all reported cases of sirenomelia also be present with BRA.

Other anomalies of the classic Potter sequence infant include a parrot beak nose, redundant skin, and the most common characteristic of infants with BRA which is a skin fold of tissue extending from the medial canthus across the cheek. The ears are slightly low and pressed against the head making them appear large. The adrenal glands often appear as small oval discs pressed against the posterior abdomen due to the absence of upward renal pressure. The bladder is often small, nondistensible and may be filled with a minute amount of fluid. In males the vas deferens and seminal vesicles may be absent, while in females the uterus and upper vagina may be absent. Other abnormalities include anal atresia, absence of the rectum and sigmoid colon, esophageal and duodenal atresia, and a single umbilical artery. Presence of a diaphragmatic hernia is also common in these fetuses/infants. Additionally, the alveolar sacs of the lungs fail to properly develop as a result of the reduced volume of amniotic fluid. Labor is often induced between 22 and 36 weeks of gestation (however, some of these pregnancies may go to term) and unaborted infants typically survive for only a few minutes to a few hours. These infants will eventually die as either a result of pulmonary hypoplasia or renal failure.

Feingold syndrome is marked by various combinations of microcephaly, limb malformations, esophageal and duodenal atresias, and sometimes learning disability or mental retardation.

Beare–Stevenson cutis gyrata syndrome is a rare genetic disorder characterized by craniosynostosis (premature fusion of certain bones of the skull, sometimes resulting in a characteristic 'cloverleaf skull'; further growth of the skull is prevented, and therefore the shape of the head and face is abnormal) and a specific skin abnormality, called cutis gyrata, characterized by a furrowed and wrinkled appearance (particularly in the face and on the palms and soles of the feet); thick, dark, velvety areas of skin (acanthosis nigricans) are sometimes found on the hands and feet and in the groin.

Additional signs and symptoms of Beare–Stevenson cutis gyrata syndrome can include a blockage of the nasal passages (choanal atresia), overgrowth of the umbilical stump, and abnormalities of the genitalia and anus. The medical complications associated with this condition are often severe and may well be life-threatening in infancy or early childhood.

Antley–Bixler syndrome presents itself at birth or prenatally. Features of the disorder include brachycephaly (flat forehead), craniosynostosis (complete skull-joint closure) of both coronal and lambdoid sutures, facial hypoplasia (underdevelopment); bowed ulna (forearm bone) and femur (thigh bone), synostosis of the radius (forearm bone), humerus (upper arm bone), and trapezoid (hand bone); camptodactyly (fused interphalangeal joints in the fingers), thin ilial wings (outer pelvic plate), and renal malformations.

Other symptoms, such as cardiac malformations, proptotic exophthalmos (bulging eyes), arachnodactyly (spider-like fingers), as well as nasal, anal, and vaginal atresia (occlusion) have been reported.

Familial multiple intestinal atresia is an inherited disorder where atresia occurs at multiple locations throughout the small and large intestines. It presents at birth and the prognosis is very poor with almost all those diagnosed with this condition dying with one month. It may be associated with combined immunodeficiency.

Fryns syndrome is an autosomal recessive multiple congenital anomaly syndrome that is usually lethal in the neonatal period. Fryns (1987) reviewed the syndrome.

CHARGE syndrome (formerly known as CHARGE association), is a rare syndrome caused by a genetic disorder. First described in 1979, the acronym "CHARGE" came into use for newborn children with the congenital features of coloboma of the eye, heart defects, atresia of the nasal choanae, retardation of growth and/or development, genital and/or urinary abnormalities, and ear abnormalities and deafness. These features are no longer used in making a diagnosis of CHARGE syndrome, but the name remains. About two thirds of cases are due to a CHD7 mutation. CHARGE syndrome occurs only in 0.1–1.2 per 10,000 live births; as of 2009 it was the leading cause of congenital deafblindness in the US.

Additional symptoms include:

- anencephaly (failure of major sections of the brain to form)

- encephalocele (cranial contents protrudes from the skull)

- cyclopia (the two eye cavities fuse into one)

- agnathia

- cleft palate

- arthrogryposis

- clubfeet

- holoprosencephaly

- spina bifida

- low-set ears

- pulmonary hypoplasia

- omphalocele

- gastroschisis

- cardiovascular disorders

- diaphragmatic hernias

- gastrointestinal atresia

- single umbilical artery

- renal abnormalities

- genu recurvatum

- hydramnios

Although genetic testing positively identifies nearly two thirds of children with CHARGE syndrome, diagnosis is still largely clinical. The following signs were originally identified in children with this syndrome, but are no longer used in to make the diagnosis alone.

- C - Coloboma of the eye, central nervous system anomalies

- H - Heart defects

- A - Atresia of the choanae

- R - Retardation of growth and/or development

- G - Genital and/or urinary defects (Hypogonadism, undescended testicles, besides hypospadias.)

- E - Ear anomalies and/or deafness and abnormally bowl-shaped and concave ears, known as "lop ears".

Ring 18 causes a wide range of medical and developmental concerns. As discussed above, people with ring 18 can have features of both distal 18q- and 18p-. The features of distal 18q- and 18p- vary greatly because of the variability of the deletion size and breakpoint locations between people. Because ring 18 can involve unique deletions of both the p and q arms of the chromosome there is twice as much reason for the variability between individuals. This variation is also partly attributable to the incidence of mosaicism, which is relatively common in people with ring 18.

- Holoprosencephaly has been reported in some people with ring 18. This is due to the deletion of the TGIF gene on the short arm of chromosome 18 in some people with ring 18.Approximately 30-40% of people with ring 18 have a congenital heart anomaly. Septal defects are the most common type of defect reported in this population.

- Hypotonia is frequently seen in the ring 18 population. Seizures, though uncommon, have been reported in people with ring 18.

- In some children without “classic” holoprosencephaly, microforms of holoprosencephaly may be noted on MRI, including missing olfactory tracts and bulbs and absent or hypoplastic corpus callosum.

- Strabismus as well as nystagmus have both been reported in infants and children with ring 18.

- Hearing loss has been reported and may be related to ear canal atresia or stenosis.

- Umbilical and inguinal hernias have been reported in a small number of people with ring 18.

- Unilateral renal hypoplasia and aplasia have both been reported in individuals with ring 18. Hydronephrosis as well as pyelonephritis have also been reported in a few individuals. Cryptorchidism, hypospadias, and micropenis have been seen in males with ring 18, while females have been reported with hypoplastic labia.

- Foot abnormalities are common within the ring 18 population. Scoliosis as well as pectus excavatum have also been frequently reported.

- Several people with ring 18 have growth hormone deficiency. Hypothyroidism has also been reported in a minority of people.

- Cognitive ability varies; according to a literature review, the degree of impairment may fall anywhere between the mild and severe ends of the spectrum.

- Facial features of ring 18 include low-set, dysplastic ears, epicanthic folds, and hypertelorism. Micrognathia has also been reported.

Sometimes babies born with choanal atresia also have other abnormalities:

- coloboma

- heart defects

- mental retardation

- growth impairment

- others (see also CHARGE syndrome)

Also any condition that causes significant depression of the nasal bridge or midface retraction can be associated with choanal atresia. Examples include the craniosynostosis syndromes such as Crouzon syndrome, Pfeiffer syndrome, Treacher Collins and Antley-Bixler syndrome.

Antley–Bixler syndrome, also called trapezoidocephaly-synostosis syndrome, is a rare, very severe autosomal recessive congenital disorder characterized by malformations and deformities affecting the majority of the skeleton and other areas of the body.

Potter sequence is the atypical physical appearance of a baby due to oligohydramnios experienced when in the uterus. It includes clubbed feet, pulmonary hypoplasia and cranial anomalies related to the oligohydramnios. Oligohydramnios is the decrease in amniotic fluid volume sufficient to cause deformations in morphogenesis of the baby.

Oligohydramnios is the cause of Potter sequence but there are many things that can lead to oligohydramnios. It can be caused by renal diseases such as bilateral renal agenesis (BRA), atresia of the ureter or urethra causing obstruction of the urinary tract, polycystic or multicystic kidney diseases, renal hypoplasia, amniotic rupture, toxemia, or uteroplacental insufficiency from maternal hypertension.

The term "Potter sequence" was initially intended to only refer to cases caused by BRA; however, it is now commonly used by many clinicians and researchers to refer to any case that presents with oligohydramnios or anhydramnios regardless of the source of the loss of amniotic fluid.