The percentages of body water contained in various fluid compartments add up to total body water (TBW). This water makes up a significant fraction of the human body, both by weight and by volume. Ensuring the right amount of body water is part of fluid balance, an aspect of homeostasis. The extracellular fluid (ECF) includes all fluids outside the cells. This fluid can be divided into three fluid departments: interstitial (in the tissue spaces) fluid, blood plasma and lymph, and specialised compartments called transcellular fluid. The extracellular fluid surrounds all the cells in the body and is in equilibrium with the intracellular fluid. So, its composition must remain fairly constant even though substances are passing into and out of the cells. The interstitial fluid, though called a fluid, is in a reality a gel-like composition made up of: water, proteoglycan molecules and collagen. The extracellular fluid constitutes 40% of total body water, with intracellular fluid making up the remaining 60%. It is relatively rich in glucose.

Fragile X syndrome is a genetic condition that causes a range of developmental problems including learning disabilities and cognitive impairment. Usually, males are more severely affected by this disorder than females.Affected individuals usually have delayed development of speech and language by age 2. Most males with fragile X syndrome have mild to moderate intellectual disability, while about one-third of affected females are intellectually disabled. Children with fragile X syndrome may also have anxiety and hyperactive behaviour such as fidgeting or impulsive actions. They may have attention deficit disorder (ADD), which includes an impaired ability to maintain attention and difficulty focusing on specific tasks. About one-third of individuals with fragile X syndrome have features of autism spectrum disorder that affect communication and social interaction. Seizures occur in about 15 percent of males and about 5 percent of females with fragile X syndrome.Most males and about half of females with fragile X syndrome have characteristic physical features that become more apparent with age. These features include a long and narrow face, large ears, a prominent jaw and forehead, unusually flexible fingers, flat feet, and in males, enlarged testicles (macroorchidism) after puberty.

From the options mentioned here, the closest diagnosis is haemophilia. This is a mixed picture, as a purpuric rash on the buttocks does not correlate with this diagnosis. However, the most appropriate diagnosis is haemophilia.

Pulmonary surfactant is a mixture of lipids and proteins which is secreted by the epithelial type II cells into the alveolar space.

Recommended regimens3 NRTI (e.g., zidovudine, lamivudine, abacavir) OR2 NRTI (e.g., lamivudine + abacavir) AND1 NNRTI (e.g., efavirenz) OR1 PI (e.g., lopinavir) OR1 INI (e.g., raltegravir)

The clinical picture suggests a vitamin K deficiency haemorrhagic disease of the new-born and requires IV vitamin K and fresh frozen plasma. This usually presents with gastrointestinal bleeding, bleeding from the umbilical stump and bruising after 2–7 days.

Congenital adrenal hyperplasia is a common cause of virilisation in females that can present as ambiguous genitalia at birth. Deficiency of the 21-alphahydroxylase enzyme is implicated in excess mineralocorticoid and androgens produced by the adrenal gland. Virilisation occurs when excess androgens are converted to testosterone in a genetically female foetus, causing the genitalia to resemble male genitalia. A deficiency of 5-alpha hydroxylase would rather decrease the production of testosterone and lead to the presentation of external female genitalia in a genetically male foetus. Autoantibodies against glutamic acid are seen in type 1 diabetes mellitus, while defects in the AIRE gene and the FOXP3 affect components of the immune system.

Case control studies are used to determine the relationship between exposure to a risk factor and the resultant outcomes. It finds patients in the general population who have a certain condition and retrospectively searches for past exposure to possible risk factors for the disease. Controls are people who do not have the disease found in the general population. This type of study is useful for rare diseases, and is less time consuming to conduct. While cohort studies can be used to study rare diseases they measure the relative risk of developing the disease over time based on exposure. Ecological or cross-sectional studies attempt take a snapshot of a whole population, and thus are inappropriate for rare diseases as larger sample numbers are needed. A randomised control trial is better suited to determine the effect of an intervention.

Among the options provided, bradycardia is a feature of raised intracranial pressure.The features of raised intracranial pressure include relative bradycardia and hypertension, altered consciousness, focal neurology and seizures.All other options are signs of shock but not raised intracranial pressure.

Mild deficiencies of 21-hydroxylase or 3-beta-hydroxysteroid dehydrogenase activity may present in adolescence or adulthood with oligomenorrhea, hirsutism, and/or infertility. This is termed nonclassical adrenal hyperplasia.Late-onset or nonclassical congenital adrenal hyperplasia (NCAH) due to 21-hydroxylase deficiency is one of the most common autosomal recessive disorders. Reported prevalence ranges from 1 in 30 to 1 in 1000. Affected individuals typically present due to signs and symptoms of androgen excess. Treatment needs to be directed toward the symptoms. Goals of treatment include normal linear growth velocity, a normal rate of skeletal maturation, ‘on-time’ puberty, regular menstrual cycles, prevention of or limited progression of hirsutism and acne, and fertility. Treatment needs to be individualized and should not be initiated merely to decrease abnormally elevated hormone concentrations.Normal Ultrasound rules out Turner’s syndrome.

Febrile seizures are convulsions that can happen when a child, most often between the ages of six months and three years, has a fever. They usually last for less than five minutes and although the child may lose consciousness, they are relatively harmless. However, sometimes they can last for up to 15 minutes and when they are termed complex febrile seizures.

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.

The x-ray is suggestive of bronchiectasis. The most probable aetiology especially considering recurrent chest infections at such a young age is cystic fibrosis.

The sinus venosus is a large quadrangular cavity which precedes the atrium on the venous side of the chordate heart. It exists distinctly only in the embryonic heart (where it is found between the two venae cavae)| however, the sinus venosus persists in the adult. In the adult, it is incorporated into the wall of the right atrium to form a smooth part called the sinus venarum, which is separated from the rest of the atrium by a ridge of fibres called the crista terminalis. The sinus venosus also forms the SA node and the coronary sinus.

Stridor is a sign of upper airway obstruction. One of the most common causes of stridor in children is laryngomalacia. In the absence of laryngomalacia, stridor presenting with respiratory distress, few chest signs and no preceding coryza symptoms or fever all point to the inhalation of a foreign object. This is common in children, with a peak incidence between 1 and 2 years of age. This child did not present with a high temperature, usually indicative of epiglottitis . The incidence of epiglottis has decreased due to the H. Influenza type b vaccine. Additionally viral croup and bronchiolitis present with upper respiratory tract infection. Asthma rarely presents with stridor but is rather associated with a wheeze.

The combination of cholestasis, congenital heart disease (mainly affecting the pulmonary vasculature) and anterior-segment abnormalities (primarily posterior embryotoxon) suggests a diagnosis of Alagille syndrome. Clinical features:The facial features are characteristic and include a prominent forehead, deep-set eyes and a pointed chin. The most common skeletal manifestation is butterfly vertebrae, a clefting abnormality of the vertebrae most often seen in the thoracic spine and described in up to 87% of cases. Radio-ulnar synostosis and short phalanges have also been described in Alagille but less frequently. Note: Pectus excavatum is a feature of Noonan syndrome, one of the differential diagnoses of pulmonary valve disease.

Benign neonatal sleep myoclonus is a condition characterised by neonatal onset myoclonic jerks during NREM. Characteristic for this disorder is the absence of electroencephalographic findings.

A lucid interval, in which the patient portrays a temporary improvement in condition after a traumatic brain injury, is especially indicative of an epidural haematoma.

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.

The most probable diagnosis for this patient is bilateral retractile testes. This a normal phenomenon in some pre-pubertal boys. Rationale:Testicular descent can continue until about 3-months of age. The pre-pubertal testis is small enough that with activation of the cremasteric reflex, they can enter the inguinal canal. This in itself is a normal finding providing the testis can be brought into the scrotum without tension and does not require surgical correction. With time the testis will lie within the scrotum. Orchidopexy for true undescended testis can be performed from 6-months of age. It is also warranted if the testes remain undescended or intra-abdominally leading to infertility.Other options:- An ascending testis is one, typically, following hernia or orchidopexy surgery that was in the testis but with time is within the inguinal canal and cannot be brought into the scrotum. Orchidopexy is required for this.- No surgery is required as when the testis enlarges with puberty it will remain within the scrotum.- The testes can be brought into the scrotum. Therefore they are not undescended.- The testes are retractile not ascending| ascending testis cannot be brought into the scrotum and would require orchidopexy.

Coeliac disease is associated with the following conditions:- Dermatitis herpetiformis- Autoimmune disorders (e.g. thyroid disease, pernicious anaemia, diabetes)- IgA deficiency- Small-bowel malignancy, particularly lymphoma, if the gluten-free diet is not followed.Serology testing: The IgA tissue transglutaminase antibody is the most sensitive and specific, compared with the anti-endomysial antibody. However, false negatives will occur in children who are IgA-deficient, and IgA levels should be taken at the same time. Other options:Distal obstruction syndrome, meconium ileus, pancreatitis and rectal prolapse are all gastrointestinal manifestations of cystic fibrosis.

PARACHUTE REFLEX: This reflex occurs in slightly older infants when the child is held upright and the baby’s body is rotated quickly to face forward (as in falling). The baby will extend his arms forward as if to break a fall, even though this reflex appears long before the baby walks.Newborn reflexes are:Rooting reflex:This reflex starts when the corner of the baby’s mouth is stroked or touched. The baby will turn his or her head and open his or her mouth to follow and root in the direction of the stroking. This helps the baby find the breast or bottle to start feeding. This reflex lasts about 4 months.Suck reflex:Moro reflex:The Moro reflex is often called a startle reflex. That’s because it usually occurs when a baby is startled by a loud sound or movement. In response to the sound, the baby throws back his or her head, extends out his or her arms and legs, cries, then pulls the arms and legs back in. This reflex lasts until the baby is about 2 months old.Tonic neck reflex:When a baby’s head is turned to one side, the arm on that side stretches out and the opposite arm bends up at the elbow. This is often called the fencing position. This reflex lasts until the baby is about 5 to 7 months old.Grasp reflex:Stroking the palm of a baby’s hand causes the baby to close his or her fingers in a grasp. The grasp reflex lasts until the baby is about 5 to 6 months old. A similar reflex in the toes lasts until 9 to 12 months.Stepping reflex:This reflex is also called the walking or dance reflex because a baby appears to take steps or dance when held upright with his or her feet touching a solid surface. This reflex lasts about 2 months.

Among the given options, lipoatrophy takes time to develop as it is a long-term complication of insulin therapy. Since it has only been two weeks since the initiation of insulin therapy, it is unlikely to occur so early.The risk of lipoatrophy is reduced with newer insulins and also can be avoided by site rotation.However, anaphylaxis, allergic reactions, infection and abscesses at the site of an insulin pump can occur in this patient as a complication of insulin therapy.

The most appropriate next step would be to request for an EEG (electroencephalogram).The two primary differential diagnoses for the clinical scenario presented would be night terrors (hypnopompic hallucinations) due to underlying narcolepsy or frontal lobe epilepsy.Though occult airway obstruction and obstructive sleep apnoea can cause sleep disturbances, the clinical scenario presented is more suggestive of neurological disorders.The hyper-motor activity, along with arm posturing (often dystonic in appearance) and multiple occurrences per night would favour epilepsy. The daytime somnolence could be secondary to the nocturnal seizures.

Certain infections and medications cause characteristic skin lesions, which are the result of hypersensitivity reactions to these agents. A skin rash characterized by the eruption of macules, papules, and target-like circular lesions is referred to as erythema multiforme. The target or iris lesions appear rounded with a red centre surrounded by a pale ring, which in turn is surrounded by a dark red outer ring. These are acute and self-limiting with a propensity for distal extremities. The most common infectious cause is the infection with herpes simplex virus 1 and 2 to a lesser extent. Other notable infectious causes of erythema multiforme include Mycoplasma pneumoniae, cytomegalovirus, HIV, hepatitis c virus, varicella zoster virus, adenovirus, and some fungal infections. Norovirus infection has not been implicated in the aetiology of erythema multiforme.

The parotid duct (Stensen’s duct), which provides an exit for the gland’s secretions, passes through the anterior edge of the gland in the superficial lobe, turns medially at the anterior border of the masseter, penetrates the buccinator, then enters the oral cavity lateral to the second maxillary molar.

Intussusception is an urgent condition that must be excluded first as it may lead to life-threatening complications.

Risk factors for neonatal death and stillbirth (weak predictive value):- African American race- Advanced maternal age- History of fetal demise- Maternal infertility- History of small for gestational age infant- Small for gestational age infant- Obesity- Paternal age- Poverty and poor quality of careSo in this case the risk factor is the parental unemployment

The most possible diagnosis is SVT. The boy is suffering from hemodynamic instability, as indicated by his cold extremities. DC cardioversion is the treatment of choice.

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%.