Carbon monoxide is a colourless gas, which is toxic to animals. It has a high affinity for haemoglobin (around 250 times greater than oxygen). It combines with haemoglobin forming carboxyhaemoglobin, which decreases the oxygen-carrying capacity of the blood, leading to a left-shift in the oxygen-dissociation curve. CO is produced endogenously in limited amounts (0.4ml per hour), but the toxic levels are higher.

The best answer is Polycystic Ovarian Syndrome (PCOS), supported by amenorrhea, obesity and acne. High insulin levels are indicative of PCOS and exclude Cushing syndrome (as this is associated with low insulin levels).

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).

This patient might have viral meningitis as he recently suffered viral parotitis(Mumps). Microscopy and culture of the CSF would show a CSF lymphocytosis.

Cases of neonatal infant ambiguous genitalia can be a great source of psychological stress for families. One of the most important next steps in managing the case is reassuring the parents that the best care will be given to the baby and then informing them about the investigations that will need to be performed before a sex can be assigned. The sex should not be guessed just by examination nor assigned by karyotyping. Thorough investigations must be completed with the help of endocrinologists for the best outcome.

90% of patients with meconium ileus have cystic fibrosis (CF). Indeed, in 10 – 15% of cases of CF, the patient presents with meconium ileus.

Precocious puberty is the attainment of normal pubertal biochemical and physical features at an abnormally early age. The age cut-offs commonly used to define precocious puberty are 8 years for females and 9 years for males. Precocious puberty may be central (true) or peripheral (false) based on the aetiology. Central precocious puberty is due to the premature activation of the hypothalamic-pituitary-gonadal axis, which in turn leads to the development of secondary sexual characteristics at an earlier than usual age. Central precocious puberty is mostly idiopathic, but other causes include congenital or prolonged, untreated hypothyroidism, congenital or acquired central nervous system pathologies, and several genetic syndromes like Silver-Russell syndrome. The other mentioned choices cause peripheral or false precocious puberty.

Answer: Torsion of a testicular hydatidThe appendix testis (or hydatid of Morgagni) is a vestigial remnant of the Müllerian duct, present on the upper pole of the testis and attached to the tunica vaginalis. It is present about 90% of the time. The appendix of testis can, occasionally, undergo torsion (i.e. become twisted), causing acute one-sided testicular pain and may require surgical excision to achieve relief. One third of patients present with a palpable blue dot discoloration on the scrotum. This is nearly diagnostic of this condition. If clinical suspicion is high for the serious differential diagnosis of testicular torsion, a surgical exploration of the scrotum is warranted. Torsion of the appendix of testis occurs at ages 0-15 years, with a mean at 10 years, which is similar to that of testicular torsion.Occasionally a torsion of the hydatid of Morgagni can produce symptoms mimicking those created by a testicular torsion| a torsion of the hydatid, however, does not lead to any impairment of testicular function.Absence of the cremasteric reflex is a sign of testicular torsion. This therefore confirms that the diagnosis is Torsion of a testicular hydatid.

Tuberous sclerosis is an autosomal dominant neurocutaneous condition associated with increased psychiatric co-morbidity. It results from the mutation of TSC1 or TSC2 tumour suppressor genes. Multiple benign tumours of the brain and other vital organs are characteristic of this disease. Important findings include subependymal nodules, bone cysts, cardiac rhabdomyoma, and learning difficulties. Lisch nodules of the iris occur in neurofibromatosis.

EPICure is a series of studies of survival and later health among babies and young people who were born at extremely low gestations – from 22 to 26 weeks.Boost II is a double-blind randomised controlled trial (RCT) comparing the effects of targeting arterial oxygen saturations between 85% and 89% versus 91% and 95% in preterm infants.OSCAR Xe is not the name of a study. Baby-OSCAR is an RCT to determine whether a confirmed large patent ductus arteriosus in very premature babies should be treated with ibuprofen within 72 hours of birth.SafeBoosC is a trial to examine if it is possible to stabilise the cerebral oxygenation of extremely preterm infants in the first 72 hours of life with the use of NIRS oximetry and a clinical treatment guideline. TOBY Xe is an RCT looking at the neuroprotective effects of hypothermia combined with inhaled xenon following perinatal asphyxia.

The boy had a renal transplant, for which he needs immune suppression. For the exogenous immune suppression an exogenous steroid is needed, which in this case is responsible for the primary Cushing syndrome manifesting with short stature. The administration of steroids before the physiological fusion of the growth plate can lead to premature fusion with permanent cessation of bone growth.

The thymus is a lymphoid organ located in the anterior mediastinum. In early life, the thymus is responsible for the development and maturation of cell-mediated immunologic functions. The thymus is composed predominantly of epithelial cells and lymphocytes. Precursor cells migrate to the thymus and differentiate into lymphocytes. Most of these lymphocytes are destroyed, with the remainder of these cells migrating to tissues to become T cells.DiGeorge’s syndrome (DGS) is a developmental abnormality affecting the thymus. The classic triad of features of DGS on presentation is conotruncal cardiac anomalies, hypoplastic thymus, and hypocalcaemia (resulting from parathyroid hypoplasia).

Prevalence, sometimes referred to as prevalence rate, is the proportion of persons in a population who have a particular disease or attribute at a specified point in time or over a specified period of time.

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.

The main aim of randomisation in a clinical trial is to remove the bias and avoid any potential confounding variables. While in double blind studies both the investigators and the patients are not aware of which group they belong in, being blind is not essential in carrying out a randomized study, nor is it essential that the randomisation be done away from the study centre. A placebo also does not facilitate randomisation, which can be done in single centre and multi-centre trials.

Tanner stage two presents with the following: Downy hair, Breast bud palpable under areola (1st pubertal sign in females).Stage 1 (prepubertal) – elevation of papilla only – no pubic hairStage 2 – breast bud forms – sparse, slightly pigmented hair on labia majoraStage 3 – Breast begins to become elevated, extends beyond areola borders – hair becomes more coarse and curlyStage 4 – increased size and elevation. Areola and papilla form secondary mound – adult like, but sparing medial thighsStage 5 – final size, areola returns but papilla remains projected – hair extends to medial thighs

Topical benzoyl peroxide is used for the treatment of mild to moderate acne vulgaris. It is actually a peeling agent and it clears the pores and reduces the bacterial cell count.

The blood-brain barrier (BBB) is a term used to describe the unique properties of the microvasculature of the central nervous system (CNS). CNS vessels are continuous nonfenestrated vessels, but also contain a series of additional properties that allow them to tightly regulate the movement of molecules, ions, and cells between the blood and the CNS.Blood vessels are made up of two main cell types: Endothelial Cells (ECs) that form the walls of the blood vessels, and mural cells that sit on the abluminal surface of the EC layer. The properties of the BBB are largely manifested within the ECs, but are induced and maintained by critical interactions with mural cells, immune cells, glial cells, and neural cells, which interact in the neurovascular unit.Astrocytes are a major glial cell type, which extends polarized cellular processes that ensheath either neuronal processes or blood vessels.This includes regulating the contraction/dilation of vascular smooth muscle cells surrounding arterioles as well as PCs surrounding capillaries. Astrocytes have been identified as important mediators of BBB formation and function because of the ability of purified astrocytes to induce barrier properties.

The inferior alveolar nerve supplies all the teeth of the respective hemimandible. It transverses the inferior alveolar canal and is a branch of the trigeminal nerve’s mandibular division. Therefore, in this case, the teeth of the right hemimandible will be numb.

Answer: Spontaneous bacterial peritonitisThe presence of periorbital and facial oedema with normal blood pressure in this toddler indicates that he has nephrotic syndrome. Nephrotic syndrome can be associated with a series of complications that can affect an individual’s health and quality of life:Spontaneous bacterial peritonitis can develop where there is ascites present. This is a frequent development in children but very rarely found in adults.Spontaneous bacterial peritonitis (SBP) is the development of a bacterial infection in the peritoneum, despite the absence of an obvious source for the infection. It is specifically an infection of the ascitic fluid – an increased volume of peritoneal fluid. Ascites is most commonly a complication of cirrhosis of the liver. It can also occur in patients with nephrotic syndrome. SBP has a high mortality rate.The diagnosis of SBP requires paracentesis, a sampling of the peritoneal fluid taken from the peritoneal cavity. If the fluid contains large numbers of white blood cells known as neutrophils (>250 cells/µL), infection is confirmed and antibiotics will be given, without waiting for culture results. In addition to antibiotics, infusions of albumin are usually administered.Signs and symptoms of spontaneous bacterial peritonitis (SBP) include fevers, chills, nausea, vomiting, abdominal pain and tenderness, general malaise, altered mental status, and worsening ascites. Thirteen percent of patients have no signs or symptoms. In cases of acute or chronic liver failure SBP is one of the main triggers for hepatic encephalopathy, and where there is no other clear causal indication for this, SBP may be suspected.These symptoms can also be the same for a spontaneous fungal peritonitis (SFP) and therefore make a differentiation difficult. Delay of diagnosis can delay antifungal treatment and lead to a higher mortality rate.

Distal renal tubular acidosis (dRTA) is characterised by a decreased hydrogen ion excretion from the alpha intercalated cells of the collecting duct of the distal nephron. The resultant acidosis causes calcium and phosphates to be released from bones to buffer the acidosis causing hypercalciuria. This precipitates calcium compounds in the kidney, predisposing it to renal stone formation. On the other hand, proximal renal tubular acidosis is characterised by an impairment in bicarbonate resorption. Both types lead to metabolic acidosis and electrolyte imbalances including potassium depletion. Children often present with failure to thrive. One way to differentiate between the two conditions is with an acid challenge test. In proximal RTA (type 2) administering an ammonium chloride load will decrease the urinary pH whereas in distal disease (type 1), the urine pH will not decrease below 5.3.

Although WPW syndrome is a type of supraventricular re-entrant tachycardia, CCBs are contraindicated in its management. This is because CCBs depress AVN conduction| the current then passes through the accessory pathway (bundle of Kent) instead, causing ventricular tachycardia.

The most probable diagnosis in this patient is Noonan syndrome.Noonan syndrome is an autosomal dominant condition characterised by short stature, heart defects (mainly pulmonary stenosis) and learning difficulties. An affected foetus can present with a significant increase in the nuchal thickness or a cystic hygroma of the neck. The condition is variable, and an affected parent is often only diagnosed after the diagnosis in the child.

Answer: Acute Epstein Barr virus infectionThe Epstein–Barr virus is one of eight known human herpesvirus types in the herpes family, and is one of the most common viruses in humans. Infection with Epstein-Barr virus (EBV) is common and usually occurs in childhood or early adulthood.EBV is the cause of infectious mononucleosis, an illness associated with symptoms and signs like:fever,fatigue,swollen tonsils,headache, andsweats,sore throat,swollen lymph nodes in the neck, andsometimes an enlarged spleen.Although EBV can cause mononucleosis, not everyone infected with the virus will get mononucleosis. White blood cells called B cells are the primary targets of EBV infection.Petechiae on the palate are characteristic of streptococcal pharyngitis but also can be seen in Epstein–Barr virus infection, Arcanobacterium haemolyticum pharyngitis, rubella, roseola, viral haemorrhagic fevers, thrombocytopenia, and palatal trauma.

Eight percentage of infantile haemangiomas are focal and solitary. Sixty percent of cutaneous haemangiomas occur on the head and neck, 25% on the trunk, and 15% on the extremities. Haemangiomas also can occur in extracutaneous sites, including the liver, gastrointestinal tract, larynx, CNS, pancreas, gall bladder, thymus, spleen, lymph nodes, lung, urinary bladder, and adrenal glands.Guidelines on the management of infantile haemangioma were released in December 2018 by the American Academy of Paediatrics stating that:Imaging is not necessary unless the diagnosis is uncertain, there are five or more cutaneous infantile haemangiomas present, or there is suspicion of anatomic abnormalities.

Hirsutism is the growth of excess hair in androgen dependent areas or in a male pattern. The phenomenon is found in conditions where there is abnormal androgen action. This can occur in adrenal lesions including congenital adrenal hyperplasia, and Cushing syndrome, or a failure to produce adequate female hormones such as PCOS and premature menopause. Similarly, drugs such as anabolic steroids, danazol and minoxidil can also cause hirsutism. Delayed puberty is unlikely to cause hirsutism.

Based on the history and clinical presentation, she most likely has iron toxicity.Iron can cause scarring of the gut mucosa. This explains her pyloric stenosis. This typically occurs at the pylorus as this is where iron tablets tend to pool and cause maximal tissue damage.Other options:- Citalopram: Selective serotonin reuptake inhibitors (SSRIs) ingestion rarely causes serious consequences. It can rarely lead to serotonin syndrome (autonomic instability, mental status change, and increased neuromuscular tone).- Ibuprofen: While it may cause gastritis, ibuprofen does not cause pyloric/intestinal stenosis.- Thyroxine: An overdose of thyroxine will cause features of hyperthyroidism which are not present in the patient in question.- Zinc: High doses of zinc can cause abdominal cramps, nausea, vomiting and diarrhoea.

The trigeminal nerve is responsible for the sensory innervation of the head, and the muscles of mastication. The nerve is divided into three branches, the ophthalmic nerve (V1) the mandibular nerve (V2) and the maxillary nerve (V3) which all exit the skull through their respective foramina. An easy way to remember these foramina is with the following mnemonic:Standing Room Only, for V1-V3 respectivelyV1- Superior orbital FissureV2- foramen RotundumV3 foramen Ovale

Precocious puberty is the attainment of normal pubertal biochemical and physical features at an abnormally earlier age. The age cut-offs commonly used to define precocious puberty are 8 years for females and 9 years for males. The onset of normal puberty is triggered by gonadotropic-releasing hormones from the hypothalamus.In most of the familial cases, the condition is transmitted by affected father. In boys, this makes up about 5% of the cases.Full adult height potential is not achieved in patients of precious puberty, although there is an advanced bone maturation.

Allergy: A history of a prior allergic-like reaction to contrast media is associated with an up to a 5-fold increase in the likelihood of experiencing a subsequent reaction. Also, any patient with a predilection to allergic reactions may predispose them to a reaction after the administration of contrast media. Given the increased risk of severe life-threatening anaphylaxis related to the administration of contrast media in the setting of the history of atopy, the risk versus benefits should be discussed before following through with the procedure. A premedication regimen may be used to reduce the risk of anaphylaxis.Asthma: A history of asthma may be indicative of a higher likelihood of developing a contrast reaction. Cardiac status: Attention must be turned to patients with significant cardiac disease (congestive heart failure, aortic stenosis, severe cardiomyopathy, and/or pulmonary hypertension), as higher volumes and osmolality of contrast material may result in an increased risk for a contrast reaction.Renal insufficiency: Contrast nephrotoxicity is defined as the rapid deterioration of renal function after the administration of contrast media when no other aetiology can be determined from the clinical records. The major predisposing risk factors include pre-existing renal insufficiency (defined as serum creatinine level >1.5 mg/dL) and diabetes. Other risk factors include dehydration, cardiovascular disease, the use of diuretics, advanced age (>70 years old), hypertension, and hyperuricemia. Obtaining multiple contrast-enhanced studies within 24 hours is also thought to increase the risk for contrast-induced nephrotoxicity. Miscellaneous: Relative contraindications to the use of high osmolality iodinated contrast media (HOCM) in patients with pheochromocytoma, sickle cell disease, and multiple myeloma have been reported. Although the administration of low osmolality or iso-osmotic contrast media may be beneficial in patients with pheochromocytoma and sickle cell disease, little evidence suggests that these agents mitigate the risks associated with multiple myeloma.