Pediatrics: 12 practice questions

Acute otitis media. Signs of AOM include bulging or a lack of movement of the tympanic membrane from a puff of air — immobility indicates fluid under pressure in the middle ear, which redness alone does not establish.

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A chronic autoimmune disease, mainly affecting the small intestine, caused by an abnormal immune system response to gluten, a protein found in wheat and other grains. The immune attack flattens the villi, destroying absorptive surface area — which is why the consequences are those of malabsorption rather than of inflammation alone.

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Decreased lung volumes with a bell-shaped chest, and a small, discrete, uniform infiltrate of 0.5 to 1 mm involving all lobes of the lung — the ground-glass appearance — with air bronchograms. The uniformity is the point: patchy or asymmetric change suggests aspiration or infection rather than surfactant deficiency.

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One is a process, the other a measurement. IUGR is defined by clinical features of malnutrition and evidence of reduced growth regardless of an infant's birth weight percentile; it can result in a baby being small for gestational age, most commonly defined as a weight below the 10th percentile. A constitutionally small baby is SGA without IUGR, and a growth-restricted baby can sit above the 10th centile.

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Iron. Excessive cows' milk displaces iron-rich foods, is itself a poor iron source, and can cause occult gastrointestinal blood loss — producing microcytic anaemia with pallor, irritability, poor appetite and, if prolonged, developmental effects. A low serum ferritin confirms it, remembering that ferritin can be elevated by any chronic inflammation. The assessment is dietary before it is haematological.

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Type 1 diabetes. The major sign is very high blood sugar, which typically manifests in children as a few days to weeks of polyuria, polydipsia and weight loss — symptoms usually appearing within weeks to a few months. The underlying mechanism is autoimmune destruction of the insulin-producing beta cells in the pancreas, so the presentation is abrupt in a previously well child, unlike the insidious course of type 2.

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Cryptorchidism is the failure of one or both testicles to descend into the scrotum, affecting about 3% of full-term and 30% of premature infant boys — but about 80% of cryptorchid testes descend by the first year of life, giving a true incidence of around 1%. A retractile testis, which can be brought into the scrotum and stays briefly, is normal and must be distinguished from a truly undescended one.

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Damage to the barrier allows proteins such as albumin, antithrombin or the immunoglobulins to pass through and appear in urine. Losing albumin drops serum oncotic pressure, and lower serum oncotic pressure causes fluid to accumulate in the interstitial tissues — oedema. The same leak explains the other features: losing antithrombin gives thrombosis, losing immunoglobulins gives infection.

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In children, rotavirus is the most common cause of severe disease; bacteria cause about 15% of cases, most commonly Escherichia coli, Salmonella, Shigella and Campylobacter. The most accurate signs of moderate or severe dehydration in children are a prolonged capillary refill, poor skin turgor and abnormal breathing, with sunken eyes, decreased activity, lack of tears and dry mouth as supporting findings.

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The presence of all or part of a third copy of chromosome 21. Incidence increases with the age of the mother, from less than 0.1% for 20-year-old mothers to 3% at age 45 — but because most births are to younger women, most affected children are born to mothers under 35, which is why screening is offered universally rather than by age alone.

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Contraction of airway smooth muscle, swelling, thickening of the airway wall due to remodelling, increased mucus production and mucus plugs. Bronchospasm and swelling reverse with treatment; remodelling does not — which is why inflammation is treated continuously rather than only when the patient wheezes. Airway inflammation persists across all patients regardless of symptoms.

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Protein loss and its consequence. The definition is proteinuria above 3.5 g per 1.73 m2 per 24 hours with hypoalbuminaemia below 3.5 g/dl — protein in the urine, low blood albumin levels and swelling. Minimal change disease is the most common cause of nephrotic syndrome in children, and the first test will be a urinalysis, which is why biopsy is not routine in a child with a typical picture who responds to steroids.

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