In the pattern of mendelian inheritance, X- linked dominant inheritance means that all who inherit the X chromosome will present with the condition. In the case of maternal x-linked inheritance sons and daughters have an equal chance of inheriting the condition as there is a 50% chance of inheriting the defective X chromosome from their mother as opposed to a non affected X chromosome from their father. However in paternal X-linked dominant inheritance, sons will be unaffected as they inherit a Y chromosome from their father while daughters are sure to inherit the defective X-chromosome.

CSF is produced mainly by a structure called the choroid plexus in the lateral, third and fourth ventricles. CSF flows from the lateral ventricle to the third ventricle through the interventricular foramen (also called the foramen of Monro). The third ventricle and fourth ventricle are connected to each other by the cerebral aqueduct (also called the Aqueduct of Sylvius). CSF then flows into the subarachnoid space through the foramina of Luschka (there are two of these) and the foramen of Magendie (only one of these).Absorption of the CSF into the blood stream takes place in the superior sagittal sinus through structures called arachnoid villi . When the CSF pressure is greater than the venous pressure, CSF will flow into the blood stream.

E. coli accounts for the majority of UTI’s in children. If this child responds well to treatment and has no recurrence of his symptoms, then no form of imaging is required, as per NICE advice for children aged 6 months to 3 years. Had the child been less than 6 months of age, then a USS at 6 weeks would be necessary.Other options:- Pseudomonas causes atypical UTI. This warrants ultrasonography within the acute illness phase as it may reflect an underlying pathology and DMSA at 4-6 months.- Recurrent UTI is defined as two or more episodes of pyelonephritis OR 1 pyelonephritis and one cystitis OR 3 or more cystitis. It requires USS at six weeks and DMSA at 4-6 months.- Septicaemia is a sign of an atypical UTI. This requires USS within the acute illness as it may reflect an underlying pathology and DMSA at 4-6 months.- Unwell 48hrs post antibiotics is a sign of an atypical UTI. This requires USS within the acute illness as may reflect underlying pathology and DMSA at 4-6 months.

There are two lateral rotators of the arm, the infraspinatus and the teres minor muscles. The infraspinatus muscle receives nerve supply from C5 and C6 via the suprascapular nerve, whilst the teres minor is supplied by C5 via the axillary nerve.

Haemolytic disease of the new-born due to ABO incompatibility is usually less severe than Rh incompatibility. One reason is that fetal RBCs express less of the ABO blood group antigens compared with adult levels. In addition, in contrast to the Rh antigens, the ABO blood group antigens are expressed by a variety of fetal (and adult) tissues, reducing the chances of anti-A and anti-B binding their target antigens on the fetal RBCs.ABO HDN occurs almost exclusively in the offspring of women of blood group O, although reports exist of occasional cases in group A mothers with high‐titre anti‐(group B) IgG

Teenagers may have poor eating habits and neglect to take their vitamin supplements. They are less likely than older women to be of adequate pre-pregnancy weight or to gain an adequate amount of weight during pregnancy. Low weight gain increases the risk of having a low birthweight baby. Weight gain is maximal during the 2nd trimester.aPTT and gallbladder emptying is decreased during pregnancy whereas d-dimers is increased.

Anorexia nervosa is an eating disorder which is characterized by distorted self-image leading to abnormally decreased calorie intake. This disorder affects multiple bodily systems, including the skin, GI, and endocrine system. Due to extreme weight loss, patients with anorexia nervosa develop cold intolerance along with bluish discoloration of their fingers, nose, and ears, which is known as acrocyanosis. This phenomenon may be due to the shunting of the blood from the peripheries to the central body systems as a reaction to hypothermia. Other notable changes in the integumentary system include extreme dryness (xerosis), lanugo hairs, decubitus ulcers, and easy bruisibility.

The structure in question is the rectus sheath. This sheath encloses the rectus abdominis muscle and thus, will be encountered by the surgeon.Note:- Midline incision: It is the most common approach to the abdomen. The structures divided during this incision are linea alba, transversalis fascia, extraperitoneal fat, and peritoneum ( with care taken to avoid the falciform ligament above the umbilicus).The bladder can be accessed via an extraperitoneal approach through the space of Retzius.- Paramedian incision: It is an incision that is made parallel to the midline. The structures divided or retracted are anterior rectus sheath, rectus (retracted), posterior rectus sheath, transversalis fascia, extraperitoneal fat, and peritoneum.- Battle incision: It is similar to a paramedian but the rectus is displaced medially (and thus denervated).- Kocher’s incision: It is an incision made under the right subcostal margin, e.g. cholecystectomy (open).- Lanz incision: It is an incision in the right iliac fossa, e.g. appendicectomy.Gridiron incision: It is an oblique incision centred over the McBurney’s point – usually used for appendicectomy (less cosmetically acceptable than LanzPfannenstiel’s incision: It is a transverse suprapubic incision, primarily used to access pelvic organs.McEvedy’s incision: It is a groin incision used for emergency repair strangulated femoral hernia.Rutherford Morrison incision: It provides an extraperitoneal approach to left or right lower quadrants. It provides excellent access to iliac vessels and is the approach of choice for first-time renal transplantation.

The most appropriate imaging modalities to be used in this child would be CT Head, C-spine and Abdomen/Pelvis and chest X-ray (CXR).The C-spine cannot be cleared, this alongside a multi-trauma presentation means a CT C-spine is indicated rather than X-rays alone. The imaging modality for blunt trauma to the chest is CXR| if this shows significant thoracic trauma, a CT chest should be considered. Other options:- CT Head and Abdomen/Pelvis with CXR and X-ray C-spine: This child is at risk of C-Spine injury following the mechanism of trauma. He had a reduced GCS, has undergone a multi-region trauma and is now intubated. NICE head injury guidelines, therefore, recommend using CT.- CT Head, C-spine and Abdomen/Pelvis X-rays: Imaging of the chest is required following blunt trauma and for endotracheal tube position.- MRI Head: If there were concerns of abnormal neurology, then spinal MRI could be considered.- Whole-body CT: It is not recommended in children in view of the high radiation doses.

Urine culture confirms a diagnosis of a UTI. A kidney ultrasound will be the next best investigation because it will help us to visualise the bladder, kidneys, and ureters to rule out any congenital obstruction in the urinary tract that might be the actual cause of infection in this 2-month old girl.

The most probable diagnosis for the patient in question is atrioventricular nodal re-entrant tachycardia (AVNRT).The presenting features of the patient are suggestive of supraventricular tachycardia (SVT). The most common form of SVT in children over 8 years old is atrioventricular nodal re-entrant tachycardia. It occurs as a result of an additional electrical circuit in or near the AV node itself.Other options:- Atrial Flutter: is a form of re-entry tachycardia within the atria which then becomes unsynchronised with the ventricles, which is not the case here. Furthermore, it is most common in babies and children with congenital heart disease.- Atrial tachycardia: is a condition where an area of atrium takes over the pacemaker activity of the heart. However, it is relatively uncommon.- Atrioventricular re-entrant tachycardia (AVRT): occurs due to an accessory electrical pathway between the atria and ventricles forming a re-entry circuit. This is the most common cause of SVT in children < 8 years old. One of the specific diagnoses of AVRT is Wolff-Parkinson-White syndrome. However, WPW syndrome is much rarer than AVNRT.- Premature atrial contractions (PACs): are very common in normal, healthy children and adolescents. Occasionally, they can give rise to the feeling of a 'skipped beat'. Fortunately, they are rarely associated with any significant underlying pathology or need to be treated.

Based on the presentation, the child most probably is suffering from a refractive error.Astigmatism, myopia and high hypermetropia could all cause these symptoms. This child has difficulty in using vision for finer tasks such as reading. Mild to moderate refractive error would not impair the child’s ability to play or even watch television as for the child in question. Note: Refractive error is the most common treatable cause of reduced vision in children all over the world! Other options:- A congenital cataract is rare and retinal dystrophy is even rarer. – Amblyopia would suggest poor vision in only one eye, something that might not cause symptoms in this age group. – Parents or teachers would have probably noticed squint if it was present.

Turner syndrome is a genetic disease that affects females. It presents with wide-spread nipples, low hairline, lymphoedema, short 4th metacarpals, high-arched palate, cardiac problems, and horseshoe kidneys.

Congenital heart diseases such as complete atrioventricular septal defects are most likely to cause large left to right shunts leading to faltering growth due to chronic severe hypoxia, pulmonary oedema, and feeding problems. Isolated atrial septal defects or ventricular septal defects result in relatively smaller shunts. Pulmonary stenosis and bicuspid aortic valve do not cause chronic systemic hypoxia. People with these conditions are often asymptomatic and only show some symptoms with intense physical activity.

Pale stools suggest obstructive jaundice. Initially, the symptoms of biliary atresia are indistinguishable from those of neonatal jaundice, a usually harmless condition commonly seen in infants. However, infants with biliary atresia develop progressive conjugated jaundice, pale white stools and dark urine.

Minimal change disease is a type of glomerulonephritis that mostly affects younger children. Proteinuria is present which leads to body oedema. But in these patients blood pressure is normal.

Puberty is a period of transitioning into adulthood by developing full reproductive potential by undergoing drastic physiological and psychological changes. For boys, it occurs around 9-16 years of age typically. The process of pubertal changes is usually divided into stages called tanner’s stages. The physiologic changes of puberty are initiated by the release of gonadotropin-releasing hormones from the hypothalamus, which then interact with numerous endogenous and environmental stimuli to bring about the physical pubertal features. Tanner stage 2 in boys is characterized by the thinning and reddening of the scrotal skin.The growth spurt of around 9cm per year is expected in boys, at the peak velocity.Testicular enlargement of >3cm commences puberty.Pubarche, in the absence of other secondary sexual characteristics, is pathological.Adrenarche is the increase in the secretion of adrenal androgens, occurring prior to increased gonadotropin release.

The sensory innervation of the external auditory meatus is provided by branches of several cranial nerves. The auriculotemporal branch of the mandibular nerve (CN V3) with the nerve to external acoustic meatus supplies the anterior and superior wall of the canal with sensory innervation. The auricular branch of the vagus nerve (CN X) supplies the posterior and inferior walls of the canal, and the facial nerve (CN VII) may also supply it due to its connection with the vagus nerve.

Answer: MittelschmerzMittelschmerz is midcycle abdominal pain due to leakage of prostaglandin-containing follicular fluid at the time of ovulation. It is self-limited, and a theoretical concern is treatment of pain with prostaglandin synthetase inhibitors, which could prevent ovulation. The pain of mittelschmerz usually occurs in the lower abdomen and pelvis, either in the middle or to one side. The pain can range from a mild twinge to severe discomfort and usually lasts from minutes to hours. In some cases, a small amount of vaginal bleeding or discharge might occur. Some women have nausea, especially if the pain is very strong.Diagnosis of pelvic pain in women can be challenging because many symptoms and signs are insensitive and nonspecific. As the first priority, urgent life-threatening conditions (e.g., ectopic pregnancy, appendicitis, ruptured ovarian cyst) and fertility-threatening conditions (e.g., pelvic inflammatory disease, ovarian torsion) must be considered. Many women never have pain at ovulation. Some women, however, have mid-cycle pain every month, and can tell by the pain that they are ovulating.As an egg develops in the ovary, it is surrounded by follicular fluid. During ovulation, the egg and the fluid, as well as some blood, are released from the ovary. While the exact cause of mittelschmerz is not known, it is believed to be caused by the normal enlargement of the egg in the ovary just before ovulation. Also, the pain could be caused by the normal bleeding that comes with ovulation.Pelvic inflammatory disease can be ruled out if the patient is not sexually active.

Chickenpox is a highly communicable viral disease caused by human (alpha) herpesvirus 3 (varicella-zoster virus, VZV). It is transmitted from person to person by direct contact (touching the rash), droplet or air born spread (coughing and sneezing).

Among the provided options, we would expect a normally developing six-month-old child to have lost Moro’s reflex.Note:The Moro reflex is present from birth and persists until 4 months of age. It is abnormal for the Moro reflex to persist much beyond this stage, and if it does, cerebral palsy should be considered.A normal 6-month old baby should be able to roll over from front to back, readily follow objects with their eyes, transfer objects from hand to hand, recognise parental voices and babble and laugh.Other options:- Having a pincer grip is more typical of a 9-12-month-old.- Although at 6 months babies are often able to sit briefly or with support, sitting steadily is typically seen at 9 months.- Starting to stand with support is more typical of a 9-12-month-old.- Waving bye-bye is more typical of a 9-12-month-old.

Cricothyroidectomy is done in life threatening condition, where an incision is made in cricothyroid membrane to establish a patent airway.

Hyperkalaemia is not to evaluate or detect AKI but rather the result of it. If one of the rest of the options is present, then AKI would be suspected.

A 10 year old child, with a history of URTI and haematuria, presents a picture consistent with a diagnosis of IgA nephropathy. This condition can present with proteinuria and generalized swelling. However, an important differentiating point from rapidly progressive GN is the duration. IgA nephropathy is usually <10 days (commonly 4-5 day history of infection).

At least seven episodes in the previous year, five episodes in each of the previous two years, or three episodes in each of the previous three years are indications for tonsillectomy. Antibiotics should be administered in the conventional dosage for proved or suspected streptococcal episodes. For now the child should be treated on a case by case basis.

Angelman Syndrome is a genetic disorder that affects the nervous system. The features of this condition include intellectual disability, a delay in developmental milestones, and movement disorders. The features occur as a result of the deletion or mutation of the maternal copy of the UBE3A gene located on Chromosome 15q. Though individuals usually inherit one copy of this gene from each parent, only the maternal gene remains active in parts of the brain. This phenomenon is known as genetic imprinting, and is also seen in Prader-Willi syndrome.

Case control studies are observational studies which retrospectively determine whether a patient might have been exposed to a risk factor for a certain disease, as compared to a control group from the general population. They can be used for a range of outcomes as well as rare diseases. One of the biggest problems with this type of study is recall bias. Research subjects may selectively remember factors that are more predictive of the disease outcome when compared to the control group. All studies should have prior power calculations before the study commences.

Hyposplenism usually occurs after the surgical removal of the spleen or in pathological processes where the splenic tissue is replaced with abnormal tissue. It is often associated with diseases such as sickle cell disease, Coeliac disease, SLE and Dermatitis Herpetiformis. Myxoedema however bears no known association with hyposplenism. Patients with hyposplenism are at risk of fulminant bacterial infection.

One-third of patients with Guillain-Barre syndrome suffer from diaphragm weakness which can lead to further respiratory complications if there is involvement of the tongue, palate, and neck muscles. Forced vital capacity (FVC) is the best way to monitor respiratory muscle function by assessing it repeatedly. Admission for ITU is suggested when FVC is below 20ml/kg and intubation recommended when FVC is 15ml/kg or below. FVC is used in any neurological disorders wherein the respiratory muscles are affected.

The type of significance test used depends on whether the data is parametric (can be measured, usually normally distributed) or non-parametric.
Parametric tests:
Student’s t-test – paired or unpaired*
Pearson’s product-moment coefficient – correlation

Non-parametric tests:
Mann-Whitney U test – unpaired data
Wilcoxon signed-rank test – compares two sets of observations on a single sample
chi-squared test – used to compare proportions or percentages
Spearman, Kendall rank – correlation.

The outcome measured is not normally distributed, i.e. it is non-parametric. This excludes the Student’s t-tests. We are not comparing percentages/proportions so the chi-squared test is excluded. The Mann–Whitney U test is a nonparametric test of the null hypothesis that it is equally likely that a randomly selected value from one sample will be less than or greater than a randomly selected value from a second sample.
This test can be used to investigate whether two independent samples were selected from populations having the same distribution.

Zona fasciculata of the adrenal produces the maximum levels of cortisol in the body.Functions of cortisol:- Increases blood pressure: permits normal response to angiotensin II and catecholamines by up-regulating alpha-1 receptors on arterioles.- Inhibits bone formation: decreases osteoblasts, type 1 collagen and absorption of calcium from the gut, and increases osteoclastic activity.- Increases insulin resistance.- Increases gluconeogenesis, lipolysis and proteolysis.- Inhibits inflammatory and immune responses.- Maintains function of skeletal and cardiac muscle.An excess of corticosteroids in the body causes various symptoms that are a part of Cushing’s syndrome.

Anorectal malformations (ARMS) are also known as imperforate anus (IA). This is an umbrella term for a group of birth defects which affect the anorectal area.During a normal bowel movement, solid waste passes from the colon (large intestine) to the rectum (the final section the colon) and through the anus. When a child has an ARM, the rectum and the anus do not develop properly.Some types of ARM can cause constipation, faecal and / or urinary incontinence, infections and other problems. Some of these problems are very minor and easy to treat, with great long-term prognosis. Others are complex and affect multiple areas of life, such as sexual function and urinary and bowel control.

Henoch–Schönlein purpura (HSP), also known as IgA vasculitis, is a disease of the skin, mucous membranes, and sometimes other organs that most commonly affects children. In the skin, the disease causes palpable purpura (small, raised areas of bleeding underneath the skin), often with joint pain and abdominal pain. It is an acute immunoglobulin A (IgA)–mediated disorder. The tetrad of purpura, arthritis, kidney inflammation, and abdominal pain is often observed.

Many factors are related with the stimulation of bone formation and growth, the pubertal growth spurt, epiphyseal senescence, and fusion, including nutritional, cellular, paracrine, and endocrine factors. An important cellular factor in these processes is the differentiation and aging of chondrocytes in the growth plate. Important paracrine factors include the many molecular pathways involved in chondrocyte differentiation, vascularization, and ossification. Oestrogen and the GH-IGF-I axis are important endocrine factors.

Neurofibromatosis type 1 (NF1) is a common autosomal dominant disease. The Lisch nodule represents one of the most common NF1 ocular manifestations.NF1 is caused by a genetic mutation which can cause tumours to grow on nerve endings| these cutaneous neurofibromas are benign tumours which grow on the skin, often first appearing during the hormonal changes that occur in teenage years. They vary in size and can appear anywhere on the body. The number of neurofibromas present differs greatly between individuals and over a lifetime Café au lait spots (coffee coloured birthmarks) are often the first and most common sign of NF1, and these are often found at birth and are usually evident by 2 years of age.Other features of NF1 can include Lisch nodules of the iris (small pigmentation in the iris which causes no disturbance to vision), skin-fold freckling (freckling/pigmentation in the groyne and armpits), plexiform neurofibromas (or sub cutaneous neurofibromas) which are diffuse tumours that grow along a nerve and are found in at least 25 % of people with NF1, optic gliomas (tumour of the optic nerve), and skeletal complications including pseudarthrosis and scoliosis. Macrocephaly (large head size) is also common, and short stature is found in around a third of people with NF1. Rare complications include a risk of malignancy, organs being compromised by neurofibromas, seizures, and hypertension.

Treating persons infected with C. trachomatis prevents adverse reproductive health complications and continued sexual transmission, and treating their sex partners can prevent reinfection and infection of other partners. Treating pregnant women usually prevents transmission of C. trachomatis to neonates during birth. Chlamydia treatment should be provided promptly for all persons testing positive for infection. Treatment delays have been associated with complications (e.g. PID) in a limited proportion of women. To minimise disease transmission to sex partners, persons treated for chlamydia should be instructed to abstain from sexual intercourse for 7 days after single-dose therapy or until completion of a 7-day regimen and resolution of symptoms if present. To minimise risk for reinfection, patients also should be instructed to abstain from sexual intercourse until all of their sex partners are treated. Persons who receive a diagnosis of chlamydia should be tested for HIV, GC, and syphilis.

Congenital TB symptoms typically develop during the second or third week of life and include poor feeding, poor weight gain, cough, lethargy, and irritability. Other symptoms include fever, ear discharge, and skin lesions.Signs of congenital TB include failure to thrive, icterus, hepatosplenomegaly, tachypnoea, and lymphadenopathy.

The mnemonic STUMPED is helpful for remembering the differential diagnosis for congenital corneal opacities: – Sclerocornea- Tears in Descemet membrane (usually due to forceps trauma or congenital glaucoma)- Ulcers (e.g. infection – rubella)- Metabolic (e.g., mucopolysaccharidosis)- Peters anomaly- oEdema – Dermoids (e.g. Goldenhar’s syndrome)

The symptoms of a partial generalized seizure are consistent with this patient.

The development of the kidney proceeds through a series of successive phases, each marked by the development of a more advanced kidney: the pronephros, mesonephros, and metanephros. The development of the pronephric duct proceeds in a cranial-to-caudal direction. As it elongates caudally, the pronephric duct induces nearby intermediate mesoderm in the thoracolumbar area to become epithelial tubules called mesonephric tubules. Each mesonephric tubule receives a blood supply from a branch of the aorta, ending in a capillary tuft analogous to the glomerulus of the definitive nephron. The mesonephric tubule forms a capsule around the capillary tuft, allowing for filtration of blood. This filtrate flows through the mesonephric tubule and is drained into the continuation of the pronephric duct, now called the mesonephric duct or Wolffian duct. The nephrotomes of the pronephros degenerate while the mesonephric duct extends towards the most caudal end of the embryo, ultimately attaching to the cloaca.

Power calculations are a important step in study design and preparation, but do not directly help with the interpretation of the results. They are used to determine how many subjects are needed in order to avoid errors in accepting or rejecting the null hypothesis. These calculations are not usually complex and for the best results, the power of the test should be set to above 80%.

Nephrogenic Diabetes Insipidus is an acquired or hereditary condition that affects the water balance. It presents with polyuria and polydipsia, leading commonly to dehydration.

Noonan syndrome is a condition that affects many areas of the body. It is characterized by mildly unusual facial features, short stature, heart defects, bleeding problems, skeletal malformations, and many other signs and symptoms.People with Noonan syndrome have distinctive facial features such as a deep groove in the area between the nose and mouth (philtrum), widely spaced eyes that are usually pale blue or blue-green in colour, and low-set ears that are rotated backwards. Affected individuals may have a high-arched palate, poor teeth alignment, and micrognathia. Many children with Noonan syndrome have a short neck, and both children and adults may have excess neck skin (also called webbing) and a low hairline at the back of the neck.Between 50 and 70 % of individuals with Noonan syndrome have short stature. At birth, they are usually a normal length and weight, but growth slows over time. Individuals with Noonan syndrome often have either a pectus excavatum or pectus carinatum. Some affected people may also have scoliosis.Most people with Noonan syndrome have some form of critical congenital heart disease. The most common heart defect in these individuals is pulmonary valve stenosis. Some have hypertrophic cardiomyopathy.A variety of bleeding disorders have been associated with Noonan syndrome. Some affected individuals have excessive bruising, nosebleeds, or prolonged bleeding following injury or surgery. Rarely, women with Noonan syndrome who have a bleeding disorder have excessive bleeding during menstruation (menorrhagia) or childbirth.Adolescent males with Noonan syndrome typically experience delayed puberty. They go through puberty starting at age 13 or 14 and have a reduced pubertal growth spurt that results in shortened stature. Most males with Noonan syndrome have undescended testes (cryptorchidism), which may contribute to infertility (inability to father a child) later in life. Females with Noonan syndrome can experience delayed puberty but most have normal puberty and fertility.Most children diagnosed with Noonan syndrome have normal intelligence, but a few have special educational needs, and some have an intellectual disability. Some affected individuals have vision or hearing problems. It has been estimated that children with Noonan syndrome have an eightfold increased risk of developing leukaemia or other cancers over age-matched peers.

The embryonic period comprises of the first 8 weeks of pregnancy. It is divided into a preembryonic phase (from the 1st to the 3rd week), in which the three germinal layers arise, and into the embryonic phase proper (from the 4th to 8th week), in which the embryonic organ anlagen arise.

Melanoma, a highly malignant tumour arising from melanocytes, is the most common life-threatening dermatological disease. Risk factors include UV radiation exposure, particularly in light-skinned individuals that are easily sunburned, increasing age, family history, and immunosuppression. Lesions that are suspicious for melanoma should be excised with complete margins. Radical excision is not routinely undertaken for diagnostic purposes and therefore if subsequent histopathological assessment determines that the lesion is a melanoma a re-excision of margins may be required.Margins of excision-Related to Breslow thicknessLesions 0-1mm thick – 1cmLesions 1-2mm thick – 1- 2cm (Depending upon site and pathological features)Lesions 2-4mm thick – 2-3 cm (Depending upon site and pathological features)Lesions >4 mm thick – 3cm

Achondroplasia is one of the commonest forms of skeletal dysplasias that lead to dwarfism. Multiple skeletal deformities are associated with it but the common cranial abnormalities are macrocephaly, frontal bossing, depressed nasal bridge, narrowed foramen magnum, and the presence of communicating hydrocephalus. A prominent maxilla is not associated with achondroplasia.

Hirschsprung’s disease is characterized by congenital absence of the autonomic plexus (Meissner’s and Auerbach’s plexus) in the intestinal wall. Usually limited to the distal colon, it can occasionally involve the entire colon or even the small bowel. There is abnormal or absent peristalsis in the affected segment, resulting in continuous spasm of smooth muscle and partial/complete obstruction. This causes accumulation of intestinal contents and dilatation of proximal segment. Skip lesions are highly uncommon. This disease is seen early in life with 15% patients presenting in first month, 60% by 1 year of age and 85% by the age of 4 years. Symptoms include severe and complete constipation, abdominal distension and vomiting. Patients with involvement of ultra-short segments might have mild constipation with intervening diarrhoea. In older children, symptoms include failure to thrive, anorexia, and lack of an urge to defecate. On examination, an empty rectum is revealed with stool palpable high up in the colon. If not diagnosed in time, it can lead to Hirschsprung’s enterocolitis (toxic megacolon), which can be fulminant and lead to death. Diagnosis involves a barium enema or a rectal suction biopsy. Barium enema shows a transition in diameter between the dilated, normal colon proximal to the narrowed, affected distal segment. It is to be noted that barium enema should be done without prior preparation, which can dilate the abnormal segment, leading to a false-negative result. A 24-hour post-evacuation film can be obtained in the neonatal period – if the colon is still filled with barium, there is a high likelihood of Hirschsprung’s disease. Full-thickness rectal biopsy is diagnostic by showing the absence of ganglion cells. Acetylcholinesterase staining can be done to highlight the enlarged nerve trunks. Abnormal innervation can also be demonstrated by rectal manometry.

Time and EventWeek 1: ImplantationWeek 2: Formation of bilaminar diskWeek 3: Formation of primitive streakFormation of notochordGastrulationWeek 4: Limb buds begin to formNeural tube closesHeart begins to beatWeek 10: Genitals are differentiated

Polycythaemia is a commonly occurring neonatal disorder, which is characterized by a venous haematocrit ≥ 65%. It increases the blood viscosity and causes microcirculatory flow impairment in the end-organs. Causes of polycythaemia are multi-factorial, but the significant risk factors are maternal diabetes, SGA, LGA or post-term birth, infants with chromosomal abnormalities, and delayed clamping of the cord. Jaundice is not a recognized risk factor for polycythaemia.

Cataracts in infants are most commonly identified by an abnormal red reflex. Due to the high risk of amblyopia in unilateral cataracts, prompt referral to a paediatric ophthalmologist is indicated. Bilateral cataracts may occur in association with several syndromes or diseases, and these children require evaluation for these systemic disorders.Retinoblastoma is rare, but it is the most common primary intraocular tumour in children. About 80% of cases are diagnosed before age 4, with a median age at diagnosis of 2 years. It most frequently presents due to an abnormal red reflex. It is one of the few life-threatening disorders encountered in paediatric ophthalmology. Intraocular retinoblastoma is very treatable, but the mortality for metastatic disease is high. Identification of tumours before systemic spread is critical. Most children with large unilateral tumours will require enucleation (surgical removal of the eye), but the eye and vision may sometimes be preserved if the tumours are identified when they are small.