Learn — Congenital anomalies, genetics & musculoskeletal

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Trisomy 21 (Down syndrome)

Down syndrome is trisomy of chromosome 21 and the commonest survivable autosomal aneuploidy, occurring in roughly 1 in 700 to 1 in 800 live births. It matters to the nurse well beyond the dysmorphic face: nearly half these babies have a structural heart defect, hypotonia makes feeding difficult from the first day, and hypothyroidism, hearing loss and atlantoaxial instability are found only if somebody actively looks for them.

Meiotic non-disjunction accounts for about 95 percent of cases and is the type whose risk rises steeply with maternal age; robertsonian translocation, usually 14;21, accounts for about 4 percent and mosaicism for about 1 percent.
Translocation Down syndrome is the one with a high recurrence risk and no relation to maternal age, so both parents must be karyotyped — a parent carrying a balanced 21;21 translocation has a 100 percent recurrence risk.
Maternal age risk is examinable: about 1 in 1500 at 20 years, about 1 in 350 at 35 years and about 1 in 100 at 40 years.
Newborn signs: marked hypotonia, brachycephaly with a flat occiput, upslanting palpebral fissures with epicanthic folds, Brushfield spots on the iris, a flat nasal bridge, protruding tongue, small low-set ears, a short neck with excess nuchal skin and a third fontanel.
Limb signs: a single transverse palmar crease, incurving of the fifth finger (clinodactyly) with a short middle phalanx, a wide sandal gap between the first and second toes, and joint hyperflexibility.
Congenital heart disease is present in about 40 to 50 percent, most characteristically the atrioventricular septal defect, so every baby needs an echocardiogram whether or not a murmur is heard.
Gut associations are duodenal atresia with its double-bubble on the abdominal film, Hirschsprung disease and imperforate anus; feed intolerance with bilious vomiting in a Down newborn is duodenal atresia until proved otherwise.
Lifelong surveillance: thyroid function at birth and periodically because both congenital and acquired hypothyroidism are common, hearing and vision testing because otitis media with effusion, refractive error and cataract are frequent, and awareness of atlantoaxial instability before anaesthesia or contact sport.
Antenatal screening is by the first-trimester combined test at 11 to 13 plus 6 weeks — increased nuchal translucency, low PAPP-A and high free beta-hCG — or the second-trimester quadruple marker with low alpha-fetoprotein, low unconjugated oestriol, high hCG and high inhibin A; only a fetal karyotype from chorionic villus sampling or amniocentesis is diagnostic.
Intellectual disability is usually mild to moderate, there is a 10 to 20 fold increase in leukaemia risk, and Alzheimer-type dementia appears early, often from the fifth decade.

Patau syndrome (Trisomy 13)

Patau syndrome is trisomy of chromosome 13, occurring in roughly 1 in 10000 live births and characterised by midline defects of the brain and face together with severe malformations of the heart, kidneys and limbs. It matters to the nurse because most of these babies die within the first weeks and the work shifts early from cure to comfort — warmth, feeding, seizure and apnoea management, and honest support of parents making decisions no one prepared them for.

The central lesion is holoprosencephaly, failure of the forebrain to divide, with its facial spectrum of midline cleft lip and palate, hypotelorism, a single central incisor and, at the extreme, cyclopia.
Other cardinal features are microcephaly with a sloping forehead, microphthalmia or anophthalmia, cutis aplasia of the scalp, postaxial polydactyly, rocker-bottom feet, omphalocele and polycystic kidneys.
Congenital heart disease is present in about 80 percent, usually ventricular septal defect, atrial septal defect or patent ductus arteriosus.
Apnoea, seizures, deafness and profound intellectual disability are the rule; central apnoea is the commonest immediate cause of death.
Survival is short — roughly half die within the first month and about 90 percent within the first year — so the care plan is set with the family early.
The discriminator against Edwards syndrome, trisomy 18: Patau is midline and polydactyly, while Edwards gives a clenched hand with the index overlapping the third finger and the fifth overlapping the fourth, a prominent occiput, micrognathia, a short sternum and rocker-bottom feet, at about 1 in 6000 to 8000 live births.
In trisomy 18 the second-trimester serum markers are characteristically all low — alpha-fetoprotein, unconjugated oestriol and hCG together — which is the opposite pattern to Down syndrome.
Diagnosis is by karyotype, which also separates full trisomy from translocation; recurrence risk after a full non-disjunction trisomy is about 1 percent, but a parental translocation raises it substantially, so parental karyotyping follows a translocation result.
Nursing care is palliative and comfort-focused: thermal care, tube or spoon feeding with expressed breast milk, positioning and suction for airway obstruction, seizure control, skin care over the cutis aplasia, pain and dyspnoea relief, and bereavement support.

Cleft lip and palate

Cleft lip and cleft palate are congenital failures of fusion of the facial processes in the first trimester — the lip and primary palate by about the seventh week and the secondary palate by about the twelfth — so they may occur alone or together, on one side or both. They matter because the newborn cannot generate suction, which turns an ordinary feed into an aspiration risk and a growth problem, and because they are among the most commonly asked congenital anomalies in staff nurse papers.

Cleft lip is more common in boys and more often left-sided and unilateral; isolated cleft palate is more common in girls. Cleft lip is visible at birth, while an isolated cleft palate is missed unless the palate is deliberately looked at and felt at the newborn examination.
The problem is the loss of suction, not the loss of swallowing: the baby is fed upright or semi-upright with a wide-based or long soft teat, a squeezable bottle, or a Haberman or Mead Johnson feeder, in short bursts with frequent burping because these babies swallow a lot of air.
The rule of 10s decides when the lip is repaired — about 10 weeks of age, 10 pounds (roughly 4.5 kg) of weight and haemoglobin of 10 g/dL; cleft lip repair is usually done at 3 to 6 months and palate repair between 9 and 18 months, before speech develops.
After cleft lip repair the baby is nursed supine or on the side, never prone, to protect the suture line, and a Logan bow or steri-strips take tension off it; after palate repair the baby is nursed prone or on the side so that secretions drain out of the mouth.
Elbow (no-no) restraints are used after both repairs to keep hands away from the suture line, released one arm at a time every 2 hours with the arm exercised and the skin checked; nothing rigid goes into the mouth for about two weeks — no spoons, straws, pacifiers, tongue depressors or oral suction catheters.
Cleft palate causes eustachian tube dysfunction, so recurrent otitis media with effusion and conductive hearing loss are expected; every child needs planned hearing assessment and many need grommets, and speech therapy for velopharyngeal incompetence and hypernasal speech.
Care is by a cleft team over years — paediatrician, plastic surgeon, ENT surgeon, orthodontist, speech therapist, audiologist and nurse — with folic acid before and in early pregnancy as the prevention message and genetic counselling for the next pregnancy.
Feeding is upright, the flow is checked so the baby is not drowned by it, and the feed is stopped for burping rather than pushed; weight gain, not the volume in the bottle, is the measure of whether feeding is working.

Neural tube defect — AFP marker

Neural tube defects are the group of malformations that follow failure of the neural tube to close between the 21st and 28th day after conception, before most women know they are pregnant - anencephaly at the cranial end, encephalocele, and spina bifida with meningocele or myelomeningocele at the caudal end. Because an OPEN defect lets fetal alpha-fetoprotein leak into the amniotic fluid and from there into the maternal circulation, maternal serum alpha-fetoprotein rises, and it is that leak which makes second-trimester screening possible.

Maternal serum alpha-fetoprotein is measured between 15 and 20 weeks (best at 16 to 18 weeks) and reported as multiples of the median; a value at or above about 2.0 to 2.5 multiples of the median is raised and triggers a detailed ultrasound.
Raised maternal serum alpha-fetoprotein is not specific to neural tube defects: it also rises with abdominal wall defects (omphalocele and gastroschisis), multiple pregnancy, underestimated gestational age, fetal death, placental bleeding and some renal anomalies - so gestational age is confirmed by ultrasound before the result is acted on.
A LOW maternal serum alpha-fetoprotein points the other way, to trisomy 21 and trisomy 18. In the quadruple test, Down syndrome gives low alpha-fetoprotein and low unconjugated oestriol with high human chorionic gonadotropin and high inhibin A, while trisomy 18 lowers all three of the older markers.
Only OPEN lesions raise alpha-fetoprotein. Spina bifida occulta, a skin-covered meningocele and a lipomyelomeningocele give a normal result, so a normal screen never excludes a closed defect - and anencephaly gives the highest values of all.
Amniotic fluid alpha-fetoprotein with acetylcholinesterase confirms an open defect; acetylcholinesterase is the specific marker that separates a true open lesion from contamination of the sample with fetal blood.
Ultrasound at the 18 to 20 week anomaly scan shows the defect directly and gives two cranial signs of the associated Chiari II malformation: the lemon sign of scalloped frontal bones and the banana sign of the cerebellum wrapped around the brainstem.
Prevention is folic acid, and it must start before conception because the tube closes in the fourth week: 400 micrograms daily from at least one month before conception through the first trimester for every woman, and 4 mg daily (the 5 mg tablet in Indian practice) for a woman with a previously affected pregnancy, on valproate or carbamazepine, with diabetes or with obesity. In pregnancy the national iron-folic acid tablet supplies 60 mg elemental iron with 500 micrograms of folic acid.
Immediate care of a baby born with an open sac: nurse prone or side-lying so nothing presses on the sac, cover it with sterile saline-soaked gauze and an occlusive plastic wrap to stop the sac drying and to prevent infection, keep the baby warm, keep the area free of faecal contamination, measure head circumference daily, and nurse in a LATEX-FREE environment because children with spina bifida develop latex allergy at a high rate. Closure is usually done within the first 24 to 72 hours.

Craniosynostosis

Craniosynostosis is premature fusion of one or more cranial sutures, so the skull cannot grow across the fused suture and grows excessively parallel to it instead - Virchow's law - producing a characteristic abnormal head shape. It matters because a single fused suture is usually only a cosmetic and reconstructive problem, whereas multiple fused sutures restrict the growing brain and cause raised intracranial pressure, visual loss and developmental harm.

Sagittal synostosis is the commonest single-suture form and produces scaphocephaly or dolichocephaly - a long, narrow boat-shaped head with a palpable midline ridge and a normal head circumference.
Bilateral coronal fusion gives brachycephaly, a short broad head with a recessed forehead; unilateral coronal fusion gives anterior plagiocephaly with a flattened forehead, an elevated orbit and eyebrow on the same side, and the harlequin eye appearance on a skull radiograph.
Metopic fusion gives trigonocephaly - a triangular, keel-shaped forehead with a visible midline ridge and hypotelorism. Lambdoid fusion is the rarest and gives true posterior plagiocephaly.
The common mimic is positional (deformational) plagiocephaly from back-sleeping, and the ear tells them apart: in positional flattening the head is a parallelogram with the ear on the flat side pushed FORWARD, the sutures are open and there is no ridge, and it improves with repositioning, tummy time and time; in lambdoid synostosis the head is a trapezoid with the ear displaced BACKWARD and downward and a palpable bony ridge.
Normal fontanelle closure is a posterior fontanelle by 6 to 8 weeks and an anterior fontanelle at 12 to 18 months, so a fontanelle that has closed early together with a ridge, an abnormal head shape or a head circumference that stops rising on the growth chart is the trigger for referral.
Diagnosis is clinical and confirmed by CT with three-dimensional reconstruction, which shows which sutures are fused and whether there is a copper-beaten inner table of raised pressure.
Syndromic craniosynostosis involves several sutures and carries a high risk of raised intracranial pressure, hydrocephalus, upper airway obstruction and proptosis with corneal exposure: Crouzon syndrome (craniosynostosis, midface hypoplasia and proptosis with normal hands), Apert syndrome (the same plus severe symmetrical syndactyly of hands and feet), Pfeiffer and Saethre-Chotzen syndromes.
Surgery is cranial vault remodelling, usually between about 6 and 12 months of age, or endoscopic strip craniectomy with post-operative helmet moulding in a young infant. Blood loss can be large in relation to the child's circulating volume, so blood is cross-matched and the child is watched closely for hypovolaemia, swelling around the eyes and cerebrospinal fluid leak after the operation.

Tracheo-oesophageal fistula

Tracheo-oesophageal fistula is an abnormal communication between the trachea and the oesophagus, arising when the primitive foregut fails to separate into its respiratory and digestive tubes in the fourth to fifth week of gestation, and it is almost always accompanied by oesophageal atresia. It is a delivery-room emergency because the baby cannot swallow her own saliva and gastric acid tracks up the fistula into the lungs, so the diagnosis is made by a catheter that will not pass, before the first feed is ever given.

Type C, proximal oesophageal atresia with a distal tracheo-oesophageal fistula, accounts for about 85% of cases. Pure atresia with no fistula (type A) accounts for about 7 to 8%, and the H-type fistula with no atresia (type E) about 4%, presenting later in infancy with coughing during feeds and recurrent pneumonia rather than at birth.
Antenatal clues are polyhydramnios, because the fetus cannot swallow liquor, together with an absent or small stomach bubble on the anomaly scan; every baby born after polyhydramnios has a catheter passed before the first feed.
The classic newborn picture is copious frothy white secretions bubbling from the mouth and nose that keep returning after suction, with coughing, choking and cyanosis at the first attempt to feed - the three Cs.
The abdomen tells you the anatomy: a DISTENDED abdomen means air is entering the stomach through a distal fistula, while a scaphoid, gasless abdomen means pure atresia with no distal communication.
Diagnosis is made by passing a firm 10 French orogastric or Replogle tube, which stops at about 10 cm from the gums, and taking a plain radiograph of the chest and abdomen showing the tube coiled in the upper pouch. Gas in the stomach and bowel confirms a distal fistula. Contrast studies are avoided because contrast in the blind pouch is aspirated.
About half of these babies have other anomalies, classically the VACTERL association - Vertebral, Anorectal, Cardiac, Tracheo-oesophageal, Renal and Limb - so an echocardiogram, renal ultrasound, spine radiograph and careful limb and perineal examination are done before surgery. The echocardiogram also identifies a right-sided aortic arch, which changes the side of the thoracotomy, and the cardiac anomaly is the strongest predictor of survival.
Pre-operative nursing is the examinable core: nil by mouth, a Replogle tube in the upper pouch on continuous or intermittent LOW-pressure suction to keep it empty of saliva, the head of the cot raised about 30 to 45 degrees to reduce reflux of acid up the fistula, thermal care, intravenous fluids with dextrose, vitamin K and prescribed antibiotics, and avoidance of bag-and-mask ventilation wherever possible because the gas passes down the fistula and distends the stomach.
Repair is by right posterolateral extrapleural thoracotomy or thoracoscopy with division and closure of the fistula and a primary end-to-end oesophageal anastomosis. A long gap may need delayed repair with a feeding gastrostomy in the meantime.
After surgery the suction catheter length is measured, marked and never exceeded, because passing a catheter beyond the marked depth can tear the fresh anastomosis. Complications are anastomotic leak, stricture needing dilatation, recurrent fistula, near-universal gastro-oesophageal reflux, and tracheomalacia with a characteristic barking or seal-like cough.
Feeding after repair follows the surgeon's contrast study; the child needs upright feeding, antireflux measures and long-term follow-up for dysphagia, and parents are taught that food impaction is a lifelong risk at the anastomosis.

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