It involves three major defects:

- A failure of the diaphragm to completely close during development

- Herniation of the abdominal contents into the chest

- Pulmonary hypoplasia

The syndrome has five characteristic findings:

- Omphalocele

- Anterior diaphragmatic hernia

- Sternal cleft with or without ectopia cordis

- Diaphragmatic pericardium defects (no diaphragmatic pericardium)

- Intracardiac defect: ventricular septal defect, diverticulum of the left ventricle, Tetralogy of Fallot

The diagnosis of congenital diaphragmatic eventration is used when there is abnormal displacement (i.e. elevation) of part or all of an otherwise intact diaphragm into the chest cavity. This rare type of CDH occurs because in the region of eventration the diaphragm is thinner, allowing the abdominal viscera to protrude upwards.

In normal Bochdalek hernia cases, the symptoms are often observable simultaneously with the baby's birth. A few of the symptoms of a Bochdalek Hernia include difficulty breathing, fast respiration and increased heart rate. Also, if the baby appears to have cyanosis (blue-tinted skin) this can also be a sign. Another way to differentiate a healthy baby from a baby with Bochdalek Hernia, is to look at the chest immediately after birth. If the baby has a Bochdalek Hernia it may appear that one side of the chest cavity is larger than the other and or the abdomen seems to be concave (caved in).

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.

A Bochdalek hernia is one of two forms of a congenital diaphragmatic hernia, the other form being Morgagni hernia. A Bochdalek hernia is a congenital abnormality in which an opening exists in the infant's diaphragm, allowing normally intra-abdominal organs (particularly the stomach and intestines) to protrude into the thoracic cavity. In the majority of patients, the affected lung will be deformed, and the resulting lung compression can be life-threatening. Bochdalek hernias occur more commonly on the posterior left side (85%, versus right side 15%). This type of hernia was first studied and documented by the Czech Anatomist and Pathologist, Vincenz Alexander Bochdalek (1801–1883).

The following features are observed with VACTERL association:

- V - Vertebral anomalies

- A - Anorectal malformations

- C - Cardiovascular anomalies

- T - Tracheoesophageal fistula

- E - Esophageal atresia

- R - Renal (Kidney) and/or radial anomalies

- L - Limb defects

Although it was not conclusive whether VACTERL should be defined by at least two or three component defects, it is typically defined by the presence of at least three of the above congenital malformations.

Anal atresia or imperforate anus is seen in about 55 percent of patients with VACTERL association. These anomalies are usually noted at birth and often require surgery in the first days of life. Sometimes babies will require several surgeries to fully reconstruct the intestine and anal canal.

Pentalogy of Cantrell (or thoraco-abdominal syndrome) is a rare syndrome that causes defects involving the diaphragm, abdominal wall, pericardium, heart and lower sternum.

Its prevalence is less than 1 in 1000000.

It was characterized in 1958.

A locus at Xq25-26 has been described.

Encephaloceles are characterized by protrusions of the brain through the skull that are sac-like and covered with membrane. They can be a groove down the middle of the upper part of the skull, between the forehead and nose, or the back of the skull. Encephaloceles are often obvious and diagnosed immediately. Sometimes small encephaloceles in the nasal and forehead are undetected.

Hydranencephaly is a condition in which the cerebral hemispheres are missing and instead filled with sacs of cerebrospinal fluid.

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

A scaphoid abdomen (sucked inwards) may be the presenting symptom in a newborn.

Treatment for a diaphragmatic hernia usually involves surgery, with acute injuries often repaired with monofilament permanent sutures.

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

Impossible Syndrome, or Chondrodysplasia situs inversus imperforate anus polydactyly, is a complex combination of human congenital malformations (birth defects).

The malformations include chondrodysplasia (improper growth of bone and cartilage), situs inversus totalis (chest and abdominal organs all a mirror image of normal), cleft larynx and epiglottis, hexadactyly (six digits) on hands and feet, diaphragmatic hernia, pancreatic abnormalities, kidney abnormal on one side and absent on the other side, micropenis and ambiguous genitalia, and imperforate anus.

Only one case of Impossible Syndrome has been reported; the infant was premature and stillborn.

A Spigelian hernia (or lateral ventral hernia) is a hernia through the Spigelian fascia, which is the aponeurotic layer between the rectus abdominis muscle medially, and the semilunar line laterally. These are generally interparietal hernias, meaning that they do not lie below the subcutaneous fat but penetrate between the muscles of the abdominal wall; therefore, there is often no notable swelling.

Spigelian hernias are usually small and therefore risk of strangulation is high. Most occur on the right side. (4th–7th decade of life.) Compared to other types of hernias they are rare.

Patients typically present with either an intermittent mass, localized pain, or signs of bowel obstruction. Ultrasonography or a CT scan can establish the diagnosis, although CT scan provides the greatest sensitivity and specificity.

Complications may arise post-operation, including rejection of the mesh that is used to repair the hernia. In the event of a mesh rejection, the mesh will very likely need to be removed. Mesh rejection can be detected by obvious, sometimes localized swelling and pain around the mesh area. Continuous discharge from the scar is likely for a while after the mesh has been removed.

A surgically treated hernia can lead to complications such as inguinodynia, while an untreated hernia may be complicated by:

- Inflammation

- Obstruction of any lumen, such as bowel obstruction in intestinal hernias

- Strangulation

- Hydrocele of the hernial sac

- Hemorrhage

- Autoimmune problems

- Irreducibility or Incarceration, in which it cannot be reduced, or pushed back into place, at least not without very much external effort. In intestinal hernias, this also substantially increases the risk of bowel obstruction and strangulation.

By far the most common hernias develop in the abdomen, when a weakness in the abdominal wall evolves into a localized hole, or "defect", through which adipose tissue, or abdominal organs covered with peritoneum, may protrude. Another common hernia involves the spinal discs and causes "sciatica". A hiatus hernia occurs when the stomach protrudes into the "mediastinum" through the esophageal opening in the diaphragm.

Hernias may or may not present with either pain at the site, a visible or palpable lump, or in some cases more vague symptoms resulting from pressure on an organ which has become "stuck" in the hernia, sometimes leading to organ dysfunction. Fatty tissue usually enters a hernia first, but it may be followed or accompanied by an organ.

Hernias are caused by a disruption or opening in the fascia, or fibrous tissue, which forms the abdominal wall. It is possible for the bulge associated with a hernia to come and go, but the defect in the tissue will persist.

Symptoms and signs vary depending on the type of hernia. Symptoms may or may not be present in some inguinal hernias. In the case of reducible hernias, a bulge in the groin or in another abdominal area can often be seen and felt. When standing, such a bulge becomes more obvious. Besides the bulge, other symptoms include pain in the groin that may also include a heavy or dragging sensation, and in men, there is sometimes pain and swelling in the scrotum around the testicular area.

Irreducible abdominal hernias or incarcerated hernias may be painful, but their most relevant symptom is that they cannot return to the abdominal cavity when pushed in. They may be chronic, although painless, and can lead to strangulation (loss of blood supply), obstruction (kinking of intestine), or both. Strangulated hernias are always painful and pain is followed by tenderness. Nausea, vomiting, or fever may occur in these cases due to bowel obstruction. Also, the hernia bulge in this case may turn red, purple or dark and pink.

In the diagnosis of abdominal hernias, imaging is the principal means of detecting internal diaphragmatic and other nonpalpable or unsuspected hernias. Multidetector CT (MDCT) can show with precision the anatomic site of the hernia sac, the contents of the sac, and any complications. MDCT also offers clear detail of the abdominal wall allowing wall hernias to be identified accurately.

The patient presents with a protrusion near the neck or between the ribs. The mass becomes prominent when the patient is straining or coughing. In asymptomatic individuals, lung hernia is incidentally detected in a chest X-ray taken for another reason. On physical examination, a prominence or mass is seen during Valsalva maneuver.

An epigastric hernia is a type of hernia which may develop in the epigastrium (upper, central part of the abdomen). Epigastric hernias usually appear in adults.

Unlike the benign diastasis recti, epigastric hernia may trap fat and other tissues inside the opening of the hernia, causing pain and tissue damage.

The causes of umbilical hernia are congenital and acquired malformation, but an apparent third cause is really a cause of a different type, a paraumbilical hernia.

The affected infant tends to be short, with a disproportionately large head. The fetal head of Infants born with iniencephaly are hyperextended while the foramen magnum is enlarged and opens through the widened pedicles. The defective neural arches directly into the upper cervical reach of the spinal canal, causing the formation of a common cavity between most of the spinal cord and the brain. The skin of the anterior chest is connected directly to the face, bypassing the formation of a neck, while the scalp is directly connected to the skin of the back. Because of this, those born with this anomaly either have a highly shortened neck or no neck at all. This causes extreme retroflexion, or backward bending, of the head in a "star-gazing" fashion. The spine is severely distorted as well along with significant shortening due to marked lordosis. The vertebrae, especially cervical, are fused together in abnormal shapes and their numbers are reduced. The spinal cord is almost always defective while the ventricular system is often dilated and the cortex is thinned. Sometimes, in the case of iniencephaly apertus, an encephalocele (sac-like protrusions of the brain through an opening in the cranium) forms.

A hernia is caused by the protrusion of a viscus (in the case of groin hernias, an intraabdominal organ) through a weakness in the containing wall. This weakness may be inherent, as in the case of inguinal, femoral and umbilical hernias. On the other hand, the weakness may be caused by surgical incision through the muscles of the abdominal/thoracic wall. Hernias occurring through these are called incisional hernias.

Femoral hernias occur just below the inguinal ligament, when abdominal contents pass through a naturally occurring weakness called the femoral canal. Femoral hernias are a relatively uncommon type, accounting for only 3% of all hernias. While femoral hernias can occur in both males and females, almost all of them develop in women because of the wider bone structure of the female pelvis. Femoral hernias are more common in adults than in children. Those that do occur in children are more likely to be associated with a connective tissue disorder or with conditions that increase intra-abdominal pressure. Seventy percent of pediatric cases of femoral hernias occur in infants under the age of one.

A reducible femoral hernia occurs when a femoral hernia can be pushed back into the abdomen, either spontaneously or with manipulation, but most likely, spontaneously. This is the most common type of femoral hernia and is usually painless.

An irreducible femoral hernia occurs when a femoral hernia becomes stuck in the femoral canal. This can cause pain and a feeling of illness.

An obstructed femoral hernia occurs when a part of the intestine becomes intertwined with the hernia, causing an intestinal obstruction. The obstruction may grow and the hernia can become increasingly painful. Vomiting may also result.

A strangulated femoral hernia occurs when a femoral hernia blocks blood supply to part of the bowel - the loop of bowel loses its blood supply. Strangulation can happen in all hernias, but is more common in femoral and inguinal hernias due to their narrow "necks". Nausea, vomiting, and severe abdominal pain may occur with a strangulated hernia. This is a medical emergency. A strangulated intestine can result in necrosis (tissue death) followed by gangrene (tissue decay). This is a life-threatening condition requiring immediate surgery.

A femoral hernia may be either reducible or irreducible, and each type can also present as either (or both) obstructed or strangulated.

The term incarcerated femoral hernia is sometimes used, but may have different meanings to different authors and physicians. For example: "Sometimes the hernia can get stuck in the canal and is called an irreducible or incarcerated femoral hernia." "The term 'incarcerated' is sometimes used to describe an [obstructed] hernia that is irreducible but not strangulated. Thus, an irreducible, obstructed hernia can also be called an incarcerated one." "Incarcerated hernia: a hernia that cannot be reduced. May lead to bowel obstruction but is not associated with vascular compromise."

A hernia can be described as reducible if the contents within the sac can be pushed back through the defect into the peritoneal cavity, whereas with an incarcerated hernia, the contents are stuck in the hernia sac.

However, the term "incarcerated" seems to always imply that the femoral hernia is at least irreducible.