The thyroid gland is one of the first endocrine glands to develop, and is formed from the endoderm of the epithelial tissue of the primitive pharynx. The mature gland is functionally made up of follicles with colloid which contain the pro hormone thyroglobulin. Thyroid hormone is synthesised at a cellular level and is stored as thyroglobulin, before its release as thyroid hormone, a major modulator of metabolism. In between the follicular cells are parafollicular, or C-cells which secrete parathyroid hormone or calcitonin which are responsible for calcium regulation in the body.

Individuals with Down syndrome are at increased risk for a variety of eye and vision disorders. Fortunately, many of these eye problems can be treated, especially if discovered at an early age. The quality of life can be further enhanced by the proper assessment and correction of eye problems. The most common eye findings include:- Refractive errors – Children with Down syndrome are more likely to need glasses than are other children. This may be due to myopia (near-sightedness), hyperopia (far-sightedness), and/or astigmatism. Refractive error may develop early in life or later on.- Strabismus – Between 20% and 60% of individuals with Down syndrome have eyes that are misaligned (strabismus). Esotropia (eyes that drift in) is most common while exotropia(eyes that drift out) occurs less frequently. Strabismus may be treated with glasses, patching and/or eye muscle surgery.- Keratoconus – A cone shaped distortion of the cornea (front layer of the eye), occurs in up to 30% of those with Down syndrome. Keratoconus is usually diagnosed around puberty and should be monitored regularly. Blurred vision, corneal thinning, or corneal haze may result from keratoconus. Keratoconus is worsened by eye rubbing; therefore, eye rubbing should be discouraged.- Cataracts – There is an increased incidence of congenital cataracts (present at birth) as well as acquired cataracts (develop later). Cataracts may progress slowly and should be monitored regularly, with surgical treatment performed when appropriate.- Glaucoma- There is an increased risk of infantile glaucoma (elevated pressure within the eye).- Blepharitis – Inflammation of the eyelids with redness at the edge of the lids and crusting around the lashes may occur and cause a feeling of dryness or burning. Treatment is with eyelid hygiene and topical antibiotics.- Tearing – Excessive tears or watering of the eyes may occur because the drainage channels are blocked or narrow (nasolacrimal duct obstruction). This may require surgical intervention.- Nystagmus – This is an involuntary back-and-forthť movement or shaking of the eyes. It can affect vision to a mild or severe degree.

The most important test recommended among the given options is the measurement of creatine kinase levels.The child presents with a gross motor developmental delay, and multiple investigations can be undertaken to confirm the diagnosis. However, the clinching point in the given clinical scenario is the presence of a positive Gower’s sign.Gower’s sign is an excellent screening test for muscle weakness, which is typically observed as an early clinical feature of Duchenne muscular dystrophy (DMD).Creatinine kinase measurement is an easy and rapid test to aid in the diagnosis. Early diagnosis has significant implications not only for the child but for the family, particularly for genetic counselling. DMD is an X-linked recessive disorder, with an abnormal gene at the X chromosome at the Xp21 locus. It is a progressive degenerative muscular condition where muscle fibres are replaced by fat and fibrosis (i.e., become dystrophic).

Bone age is a valuable tool for determining the skeletal maturation in children. An X-ray of the left hand and wrist or knee is used to calculate bone age, which is then compared with the chronological age of the subject to know if the bone age is advanced or delayed. Certain standardized methods are used to score skeletal maturity; most common methods are the Tanner-Whitehouse (TW) and Greulich-Pyle (GP) methods. The growth plate comprises a resting zone, a proliferative zone, hypertrophic cartilage zone, calcified cartilage zone, and then the ossification zone. This is the zonal distribution from the epiphysis to the diaphysis. After the closure of growth plates, spinal growth still occurs to some extent, adding up to the final height. The growth plates in boys close at around 17 to 19 years of age, while in girls, they close at around 13 to 15 years.

Answer: Do not operate and review the patient several weeks laterAir weapon injuries in children should be managed in the same way as any low velocity gun shot injury. Subcutaneous pellets are best removed. Urgent specialist referral is indicated for cranial, ocular, chest, abdominal, or vascular injuries as they may require emergency surgery. Cardiac injuries may be rapidly fatal. Penetrating abdominal injuries involving hollow viscera or major blood vessels need prompt exploration and repair. Intracranial air weapon pellets should be removed if possible. A pellet in lung parenchyma or muscle may be safely left in situ but there is a risk of infection. A pellet that has penetrated a joint or is associated with a fracture requires skilled orthopaedic management. A pellet lodged near a major blood vessel or nerve should ideally be removed. The possibility of intravascular embolism must be considered if the pellet is absent from a suspected entry site and there is no exit wound; numerous examples of arterial and venous embolism of an air weapon pellet in children have been described.In this case, the child seems well so there is no need to operate. He should be reviewed several weeks later.

One of the most common congenital viral infections is cytomegalovirus infection. It is caused by herpesvirus type 5. The clinical features include failure to thrive, intellectual disability, epilepsy, and microcephaly. The most common clinical complication is sensorineural deafness. The drug of choice for the treatment of neonatal CMV infection is ganciclovir, an anti-viral drug that has shown to prevent deafness.

Penetrance is defined as the percentage of individuals having a particular mutation or genotype who exhibit clinical signs or phenotype of the associated disorder or genotype.Gaucher disease is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

As this boy has experienced significant dry spells in the past, it is unlikely that a structural abnormality is causing the enuresis. The only therapies that have been shown to be effective in randomized trials are alarm therapy and treatment with desmopressin acetate or imipramine. Bladder training exercises are not recommended. Desmopressin acetate is the preferred medication for treating children with enuresis.

Relative risk is the probability of an outcome occurring in an exposed group as compared to the probability of that outcome in an unexposed group. In the scenario given, 50% of the children exposed developed the disease while only 10% of the children who were unexposed developed the disease. The relative risk was therefore 50/10=5. There is no further information about whether the study was controlled, the confidence interval, or the type of study. It therefore cannot be confirmed whether the chemical is causative and if it should be avoided.

Coarctation of the aorta is one of the serious forms of congenital heart diseases Occurring in about 1 in 2,500 births. It is characterized by a congenitally narrowed proximal thoracic aorta. Coarctation can occur in isolation but can accompany other cardiac lesions, including a bicuspid aortic valve in 70% of the cases and berry aneurysms in 10% of the cases. Coarctation of the aorta is commonly found in association with Turner’s syndrome, Edward’s syndrome, and Patau syndrome.

In the final result of this double blind study, 25% or one in four of patients who received the treatment responded positively. Though the difference is significant at P<0.05, it is better to present this as a significant difference at 0.4%. The number needed to treat (NNT) is defined as the inverse of the absolute risk reduction. Taking this as 0.25 (25%), the NNT is 1/0.25 = 4. However given the 95% confidence interval is between 10-50% for absolute risk reduction, the NNT with 95% CI is between 2 and 10. Therefore we cannot say with certainty that the NNT is at least 4.

Based on the clinical scenario provided, the most probable diagnosis for this patient would be tuberous sclerosis which is an autosomal dominant condition.Among the options provided, only Neurofibromatosis Type 1 is inherited by an autosomal dominant pattern. Other options:- Beckwith-Wiedemann syndrome is an example of an imprinting disorder and results from abnormalities of inheritance or methylation of chromosome 11p15.- Cystic fibrosis is an autosomal recessive condition.- Duchenne Muscular Dystrophy is an example of an X-linked recessive condition.- Hypophosphataemic (Vitamin D resistant) rickets is an X-linked dominant condition.

Colonic Polyposis and neoplasia are often seen in Cowden Syndrome which is a hamartomatous polyposis syndrome. Patients with Cowden syndrome have an increased risk for colorectal cancer.

ADH primarily acts on the collecting ducts.Other options:- The juxtaglomerular apparatus is the site of renin production.- The proximal tubule conducts isosmotic reabsorption of about 60% of sodium chloride and volume. Most of the glucose, amino acids, potassium and phosphate are absorbed here.- The loop of Henle is the site of 25% of sodium reabsorption. Active Chloride transport provides the basis for the counter current multiplier aiding urinary concentration.- The distal convoluted tubule is impermeable to water and acts via active sodium chloride absorption to dilute urine.

The boy presented with mild hypoglycaemia and should be managed at home with fast-acting carbs. He should not sleep immediately. His parents should monitor his blood glucose every hour without letting him sleep in between.

The most common cause of iron deficiency anaemia in children in developing countries is parasitic infection (hookworm, amoebiasis, schistosomiasis and whipworm).

Diarrhoea is defined as having three or more loose or liquid stools per day, or as having more stools than is normal for that person. Severe diarrhoea, causing fluid loss and loss of bicarbonate, will result in marked dehydration and metabolic acidosis.

Broca’s area is usually supplied by branches from the middle cerebral artery and thus will be spared when the anterior cerebral artery is occluded.Note:The two internal carotid arteries and two vertebral arteries form an anastomosis known as the Circle of Willis on the inferior surface of the brain. Each half of the circle is formed by:1. Anterior communicating artery2. Anterior cerebral artery3. Internal carotid artery4. Posterior communicating artery5. Posterior cerebral arteries and the termination of the basilar arteryThe circle and its branches supply the corpus striatum, internal capsule, diencephalon and midbrain.

Human breast milk composition is best suited to meet all the growth and development requirements of a baby. It contains numerous biochemicals ranging from macronutrients, micronutrients, minerals, immunoglobulins, inflammatory markers, and growth factors. The major bioactive factors found in human breast milk are: immunoglobulins (IgA, IgG, and IgM), cells (macrophages and stem cells), growth factors (epidermal growth factor, tumour necrosis factor-alpha, transforming growth factor-beta, and vascular endothelial growth factor), cytokines, chemokines, hormones, metabolic hormones, glycans, and mucins.

The external aspect of the tympanic membrane is lined by stratified squamous epithelium. Clinical correlation: Following middle ear infections, this type of epithelium can migrate into the middle ear through a perforated tympanic membrane.The ear is composed of three anatomically distinct regions: – External ear: Auricle is composed of elastic cartilage covered by skin. The lobule has no cartilage and contains fat and fibrous tissue. External auditory meatus is variable in length, measuring approximately 2.5cm long in fully grown children. Lateral third of the external auditory meatus is cartilaginous, and the medial two-thirds is bony. The greater auricular nerve innervates the region. The auriculotemporal branch of the trigeminal nerve supplies most of the external auditory meatus and the lateral surface of the auricle. – Middle ear: It is the space between the tympanic membrane and cochlea. The aditus leads to the mastoid air cells is the route through which middle ear infections may cause mastoiditis. Anteriorly the eustachian tube connects the middle ear to the nasopharynx. The tympanic membrane consists of an outer layer of stratified squamous epithelium, a middle layer of fibrous tissue and an inner layer of mucous membrane continuous with the middle ear. The chorda tympani nerve passes on the medial side of the pars flaccida. The glossopharyngeal nerve and pain innervate the middle ear. Thus, pain may radiate to the middle ear following tonsillectomy. – Ossicles:Malleus attaches to the tympanic membrane (the Umbo). Malleus articulates with the incus (synovial joint). Incus attaches to stapes (another synovial joint). – Internal ear:It consists of the cochlea, semicircular canals, and vestibule. Organ of Corti is the sense organ of hearing and is located on the inside of the cochlear duct on the basilar membrane. Vestibule accommodates the utricle and the saccule. These structures contain endolymph and are surrounded by perilymph within the vestibule. The semicircular canals lie at various angles to the petrous temporal bone. All share a common opening into the vestibule.

The most appropriate action in this baby would be to perform HIV PCR and commence cART and PCP prophylaxis if HIV positive.Treatment guidelines for HIV-positive infants state that all should receive combination antiretroviral therapy (cART) and Pneumocystis jiroveci pneumonia (PJP) prophylaxis, irrespective of CD4 count or viral load.

According per the national guidelines, 5 inflation breaths should be given with a gas pressure of 30cmH2O for term babies. Each breath should be given for 2-3 seconds. Pre-term babies should be aerated with a lower pressure of 20-25cmH2O.

Normal QT interval in a 6 months old baby is < 0.44 seconds. A duration exceeding this value is referred to as QT interval prolongation, which is associated with some important congenital syndromes that include Brugada syndrome which is characterized by vasovagal syncope and sudden cardiac death, Jervell and Lange-Nielsen syndrome which is associated with congenital deafness, Andersen syndrome which is marked by bone deformities, and Timothy syndrome with associated heart disease and immunodeficiency. Romano-Ward syndrome is the commonest cause of congenital QT prolongation with no associated extra-cardiac manifestations. Lown-Ganong-Levine syndrome is characterized by a shortened PR interval and a normal QRS duration.

Alopecia areata is seen in 6-8.8% of patients with Down syndrome, but only 0.1% of patients with alopecia areata have Down syndrome. The high frequency of alopecia areata in patients with Down syndrome suggests that a genetic linkage for alopecia areata may exist on chromosome 21.

Breast feeding should be continued for babies with breast milk jaundice as this is a benign condition.

Breast milk jaundice is a type of jaundice associated with breast-feeding. It typically occurs one week after birth. The condition can sometimes last up to 12 weeks, but it rarely causes complications in healthy, breast-fed infants. The exact cause of breast milk jaundice isn’t known. However, it may be linked to a substance in the breast milk that prevents certain proteins in the infant’s liver from breaking down bilirubin. The condition may also run in families. Breast milk jaundice is rare, affecting less than 3 percent of infants. When it does occur, it usually doesn’t cause any problems and eventually goes away on its own. It’s safe to continue breast-feeding.

The most probable cause for the patient’s symptoms is intussusception.Intussusception is a condition in which part of the intestine folds into the section next to it. It most commonly involves the small bowel and rarely the large bowel. Intussusception doesn’t usually require surgical correction. 80% of cases can be both confirmed and reduced using barium, water-soluble or air-contrast enema. However, up to 10% of cases can experience recurrence within 24 hours after reduction, warranting close monitoring during this period.Other options:- Enteric duplication: a duplication cyst could give all these features, although it may contain sufficient gastric epithelium to produce a positive Meckel’s scan. However, this is comparatively rare. – Meckel’s diverticulum: Scintigraphy has poor sensitivity making the possibility of a bleed from a Meckel’s diverticulum a genuine differential for this patient. However, considering the presence of features of bowel obstruction in the patient, a Meckel’s diverticulum bleeding and obstructing at the same time would be a rare phenomenon. – Midgut volvulus: It is also a plausible differential in this patient. However, for the given age group, a midgut volvulus is relatively uncommon compared to intussusception. – Acute appendicitis: While it is true that appendicitis can present acutely with a palpable mass and bowel obstruction, it rarely presents with rectal bleeding.

Bitemporal hemianopia is a characteristic finding seen in patients with optic chiasm lesion.The pituitary gland is situated within the pituitary fossa. Just above the pituitary fossa is the optic chiasm and so any expanding masses from the pituitary gland commonly press on it, causing bitemporal hemianopia.Other options:- Compression of the optic nerve would not cause more severe, generalised visual loss. Also, the optic nerve is not anatomically related to the pituitary gland and so is unlikely to be directly compressed in the presence of a pituitary tumour.- The optic tract is again not closely anatomically related with the pituitary gland and so is unlikely to be directly compressed in the presence of a pituitary tumour. Also, damage to the optic tract on one side would cause homonymous hemianopia.- The lateral geniculate nucleus is a centre of cells in the thalamus and is unlikely to be compressed by a pituitary tumour. Its function is to convey sensory information from the optic tract to more central parts of the visual pathway.- The Edinger-Westphal nucleus is located at the level of the superior colliculus in the midbrain and so may not be compressed by an enlarging pituitary tumour.Other visual defects:- Left homonymous hemianopia: It is the visual field defect to the left, due to the lesion of the right optic tract.- Homonymous quadrantanopias are seen in parietal (inferior homonymous quadrantopia) and temporal lobe lesions (superior homonymous quadrantopia). Mnemonic: PITS (Parietal-Inferior, Temporal-Superior)A congruous defect means complete or symmetrical visual field loss, and conversely, an incongruous defect is incomplete or asymmetric.Incongruous defects suggest an optic tract lesion, while congruous defects suggest optic radiation or occipital cortex lesion.

Stevens-Johnson syndrome (SJS) is a type of severe skin reaction. The most common cause is certain medications such as lamotrigine, carbamazepine, allopurinol, sulphonamide antibiotics, and nevirapine.

Cortisol is secreted in a circadian pattern.The secretion of cortisol is regulated by the suprachiasmatic nucleus located in the hypothalamus.Other options:- FSH, LH, GH and prolactin are secreted in a pulsatile pattern, i.e. these hormones are secreted in an episodic manner rather than continuously.- Thyroxine is secreted in a continuous pattern, not pulsatile.- The secretion of ACTH is in response to stress.Secondary to stress, the hypothalamus secretes corticotrophin releasing hormones, which are transported to the pituitary gland via the hypophyseal-portal system. ACTH is then released by the pituitary gland and binds to its receptor on the adrenal gland, which releases cortisol.