Intestinal pseudo-obstruction (IPO), patent ductus arteriosus (PDA), and natal teeth (NT) have been described as a lethal syndrome in the newborn. Two male siblings have been reported by Harris et al. in 1976, and it may be speculated whether these cases represent a broadening of the clinical phenotype of X-linked chronic idiopathic neuronal IPO, as defined more than 20 years later.
Both patients described by Harris et al. were born at term after uneventful pregnancies; they were male and apparently healthy at birth . Meconium was not passed, however, and the neonates started to vomit bile-stained material shortly after birth, so they were referred for diagnostic imaging of the gastrointestinal tract. Radiographs showed delayed gastric emptying and air-fluid levels suggestive of intestinal obstruction, midgut malrotation, and a relatively small colon. Beyond that, a left diaphragmatic hernia was discovered in one of the patients. These findings were confirmed intraoperatively, when the children were intervened for intestinal malrotation and, in the case of the firstborn, organ herniation through the diaphragmatic opening. Even though no anatomic obstruction of the digestive tract was demonstrable, gastrointestinal motility could not be stimulated after surgery in either case, and signs and symptoms of intestinal obstruction persisted until the boys' death at 6 weeks and 5 months of age, respectively. Of note, the older brother was found to have a ventral hernia when undergoing reoperation.
Additionally, auscultation revealed heart murmurs consistent with PDA in both patients. During the second week of life, the older brother presented symptoms of cardiac failure. He responded poorly to medical therapy and underwent cardiac catheterization, which confirmed the presence of a large PDA. As for the younger sibling, he had a systolic murmur best heard at the left sternal border. His PDA was confirmed by means of electrocardiography and radiography.
The older brother had two mandibular teeth and similar observations were made in the second patient.
The triggers of this syndrome remain unknown, so the diagnosis is based on the presence of characteristic clinical findings.
Although hematological abnormalities were not reported by Harris et al., the possibility of large-platelet thrombocytopenia occurring in the setting of this syndrome shall be mentioned. This, based on a publication by FitzPatrick and colleagues, who wrote about three male relatives with IPO and PDA . Additional findings described in these patients were dysmorphic facial features, infantile esotropia, atrial septal defect, hydronephrosis, and cryptorchidism. It has not yet been clarified whether both families were affected by the same disease, but targeted investigations of possible future cases may shed some light on this issue. In this context, genetic studies should also be carried out to confirm the presence or absence of FLNA mutations .
Only symptomatic treatment can be provided to affected individuals and must address IPO, PDA, and NT individually.
Treatment of IPO is challenging and requires a multidisciplinary effort combining nutritional, surgical, and pharmacological therapies. Nutritional support aims at the restoration of water and electrolyte balance and the maintenance of an adequate caloric intake. Oral food intake is preferred over enteral nutrition with feeding tubes if the patient is able to eat by mouth. In most cases, however, parenteral nutrition becomes necessary, and patients need to be closely monitored for complications such as liver failure, thrombosis, infection, and sepsis . In fact, one of the patients characterized by Harris et al. died of sepsis related to parenteral nutrition . One way to minimize complications of parenteral nutrition and to concomitantly relieve symptoms is surgery. Its role in IPO management, however, has long since been disputed: It is not curative of the disease and is associated with considerable morbidity and mortality. So when to revert to surgery? Venting ostomy placement may be indicated when the decompression of distended gastrointestinal segments can no longer be realized by nasogastric or rectal tubes or endoscopically . Also, surgical interventions may be required in emergency situations, and comorbidities such as diaphragmatic hernia may imply the need for surgery independent of IPO . Both nutritional support and surgical treatment are generally complemented with pharmacological therapies. Prokinetics, antiemetics, and analgesics are most commonly applied to this end, and small intestinal bacterial overgrowth may be prevented by non-absorbable antibiotics . Finally, serious complications of any of the aforementioned treatment strategies and poor quality of life on standard regimens are indications to intestinal or multivisceral transplantation .
The surgical ligation of PDA is performed in case of cardiac dysfunction or respiratory failure, as described by Harris et al. . Their patient did not respond to pharmacological treatment, which likely consisted in the intravenous or oral administration of indomethacin, ibuprofen, or acetaminophen. Asymptomatic or mildly symptomatic PDA warrant a conservative approach and may close spontaneously .
Supernumerary NT or teeth that are loose, pose a risk of injury to intraoral tissues, or interfere with breastfeeding should be removed. Otherwise, no treatment is necessary .
Both children described in the original case report succumbed to their disease. One of the boys died at the age of 6 weeks, the other one lived to be five months old. The older brother died despite repeated surgery for IPO and PDA ligation .
Considered individually, neither of the conditions defining this syndrome is universally lethal. The combination of IPO and PDA has later been said to "have a good prognosis with supportive therapy" , and treatment options have definitely improved since the 1970s. Notwithstanding, IPO is still related to mortality rates of up to 30% and is associated with significant morbidity . It may require lifelong treatment to increase intestinal motility, control abdominal pain, and meet the nutritional needs of the patient, or intestinal transplantation. Its profound impact on life quality is undeniable and confirmed by the high rates of suicide of IPO patients .
Generally speaking, PDA has an excellent prognosis in term infants with normal birth weights . The health and immunological status of patients with IPO, however, may negatively affect the outcome. Available literature contains descriptions of four IPO patients who underwent PDA ligation, namely the two brothers described by Harris et al. - who died of IPO complications - and the two male children presented by FitzPatrick and colleagues - who recovered well  .
NT don't usually pose a serious health problem as long as aspiration is avoided .
The fact that two siblings presented with identical signs and symptoms is highly suggestive of a genetic disorder. Yet, the underlying mutation remains unknown. The authors of the original case report proposed an X-linked recessive pattern of inheritance, whereby this hypothesis is built on vague claims regarding the patients' family history. In detail, the patients' mother had four sisters but no brothers, and her mother was one of seven with only one male surviving infancy. These observations are in agreement with the presence of an X-linked lethal factor, although the possibility of coincidence as an explanation for this particular distribution of sexes should not be neglected. In this line, autosomal recessive inheritance is also plausible .
Congenital IPO has been related to distinct gene defects and environmental influences. On the one hand, IPO is known to be part of different mitochondrial disorders, where gastrointestinal complaints are generally most prominent. Mitochondrial neurogastrointestinal encephalomyopathy is one of these disorders . IPO has also been linked to mutations of genes L1CAM, RAD21, ACTG2, and SOX10, which give rise to complex conditions such as hydrocephalus with congenital idiopathic IPO, Mungan syndrome, visceral myopathy, and Waardenburg syndrome . All of these conditions are rare and differ considerably from the disease described in this article, but there's a single case report that may be of increased interest here: Two brothers and a maternal uncle have been diagnosed with familial IPO and PDA, and there are numerous similarities between the patients described in that publication - who have been diagnosed with X-linked chronic idiopathic neuronal IPO - and those presented by Harris and colleagues  . X-linked chronic idiopathic neuronal IPO has later been associated with mutations of the FLNA gene, which encodes for filamin A , and it would be intriguing to see whether there are female carriers of a pathogenic FLNA variant among surviving members of the index family.
With regard to environmental factors inducing IPO, prenatal exposure to alcohol has been named as a possible cause . However, there is no indication that the two boys described by Harris et al. would have been exposed to the toxic effects of alcohol.
Data regarding the epidemiology of congenital IPO are scarce, which is at least partly due to the lack of specific diagnostic criteria. One of the few studies available has been carried out in the United States and suggests its incidence to be approximately 1 in 40,000 live births . The vast majority of cases is sporadic, with familial cases accounting for 3-17% of all cases, according to different authors  . The boys with IPO, PDA, and NT, as described by Harris and coworkers, fall into this category. They were born to healthy, non-consanguineous parents in the United States . To date, they remain the only patients ever reported with this particular phenotype. It should be noted, though, that there are single case reports describing largely similar conditions that may or may not correspond to the same entity  . Either way, the co-occurrence of IPO and PDA continues to be an exceedingly rare event.
The pathogenetic mechanisms leading to syndromic IPO, PDA, and NT remain poorly understood. This is primarily due to knowledge gaps regarding the etiology of the disease. If one assumed this syndrome to be related to mutations of the FLNA gene, as is X-linked chronic idiopathic neuronal IPO, some general statements could be made.
Filamin A is a large cytoskeletal protein that cross-links the actin cytoskeleton into orthogonal networks and modulates the cellular response to chemical and mechanical environmental factors by regulating changes in their shape and motility . Furthermore, neuronal intestinal dysplasia could be demonstrated by the histopathological examination of biopsy specimens obtained from one of the patients with X-linked chronic idiopathic neuronal IPO . Loss-of-function FLNA mutations may thus entail abnormalities of the cytoskeleton of enteric neurons, interfere with their structure and function, and induce neuronal IPO .
No recommendations can be given to prevent this rare syndrome and prenatal diagnoses are not yet feasible. Notwithstanding, male children born to mothers who are known to carry the causal gene defect may benefit from close monitoring from birth.
In 1976, Harris and colleagues reported the unusual co-occurrence of IPO, PDA, and NT . Additional cases have not been described to date, although there was at least one more family - this one from Scotland - with a genetic predisposition to IPO and PDA . The Scottish patients presented with IPO, PDA, and large-platelet thrombocytopenia, and the authors pointed out that IPO and large-platelet thrombocytopenia had been observed in yet another, unrelated patient, who was attended in England . Finally, X-linked IPO has been reported in Italy, although neither PDA nor thrombocytopenia has been noted in this case  . It cannot currently be confirmed if all these cases or at least part of them correspond to the same entity, which is why the present article focuses on the original case report by Harris et al.
Natal teeth (NT), patent ductus arteriosus (PDA), and intestinal pseudo-obstruction (IPO) have been described as a rare syndrome in the newborn: