Prevalence:

This is the proportion of individuals in a population who have a specific condition, disease, or attribute at a given point in time or over a specific period.

Incidence:

This is the number of new cases of a specific condition, disease, or attribute that develop in a population during a specified period of time.

Specificity:

This refers to the ability of a test to correctly identify those without the condition (true negative rate).

Sensitivity:

This refers to the ability of a test to correctly identify those with the condition (true positive rate).

Probability:

This is a measure of the likelihood that an event will occur. In the context of diseases, it can refer to the likelihood of developing a condition.

A preterm with respiratory distress syndrome presents with the condition as a result of immature lungs and inadequate surfactant production. Management of RDS therefore includes surfactant therapy, oxygen administration and mechanical ventilation, as well as measures such maintaining acid base levels and blood haemoglobin in an intensive care unit. Dexamethasone is not shown to be particularly effective when given to a preterm, but can however be used to prevent or decrease RDS severity when given to the mother before delivery.

The T wave represents ventricular repolarization. Other options:- P wave:Depolarization that spreads from the SA node throughout the atria. The wave lasts 0.08 to 0.1 seconds (80-100 ms).The isoelectric period after the P wave represents the time in which the impulse is travelling within the AV node.- P-R interval:Time from the onset of the P wave to the beginning of the QRS complex. The wave ranges from 0.12 to 0.20 seconds in duration.Represents the time between the onset of atrial depolarization and the onset of ventricular depolarization- QRS complex:It represents ventricular depolarization. The duration of the QRS complex is normally 0.06 to 0.1 seconds.- ST-segment:The isoelectric period following the QRS. It represents the period in which the entire ventricle is depolarized and roughly corresponds to the plateau phase of the ventricular action potential- U wave: It is a small positive wave which may follow the T wave. It represents the last remnants of ventricular repolarization.- Q-T intervalIt represents the time for both ventricular depolarization and repolarization to occur, and therefore roughly estimates the duration of an average ventricular action potential.The interval ranges from 0.2 to 0.4 seconds depending upon heart rate.At high heart rates, ventricular action potentials shorten in duration, which decreases the Q-T interval. Therefore the Q-T interval is expressed as a corrected Q-T (QTc) by taking the Q-T interval and dividing it by the square root of the R-R interval (interval between ventricular depolarizations). This allows an assessment of the Q-T interval that is independent of heart rate.The normal corrected Q-Tc interval is less than 0.44 seconds.

Germinal matrix/intraventricular haemorrhage (GM/IVH) is a complication of premature delivery that can result in life-long medical and developmental consequences.Loss of autoregulation of cerebral blood flow is a pathophysiologic feature of germinal matrix/intraventricular haemorrhage (GM/IVH). Prematurity itself results in derangements in cerebral autoregulation. In some patients, a history of additional events that result in loss of autoregulation can be obtained. Furthermore, events that can result in beat-to-beat variability of cerebral blood flow may be identified in some patients.There may be no symptoms. The most common symptoms seen in premature infants include:- Breathing pauses (apnoea)- Changes in blood pressure and heart rate- Decreased muscle tone- Decreased reflexes- Excessive sleep- Lethargy- Weak suck- Seizures and other abnormal movements

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.

Based on the presentation, the patient is probably a case of Crohn’s disease. The first-line treatment of Crohn’s disease is exclusive enteral nutrition.Exclusive enteral nutrition (EEN)This involves drinking a protein-based formula exclusively for 6–8 weeks. It has been shown to have superior mucosal healing when compared with steroids. Furthermore, it is nutritionally advantageous when compared to steroids and does not have the side-effect profile of steroids.Other options:- Intravenous steroids: This is the first-line treatment for ulcerative colitis (UC) or Crohn’s disease if there is rectal disease (which is not the case here). Side-effects include adrenal suppression, behavioural effects, osteopenia and changes in adipose tissue distribution.- Oral steroids: This can be used if EEN is not possible. However, the side-effect profile is less favourable and is not as effective concerning mucosal healing.- Parental nutrition and surgery: They may be occasionally required in severe cases that have failed first-line therapy.

The most probable diagnosis for this patient would be Crohn’s disease.Crohn’s disease:An inflammatory bowel disease which can affect any part of the bowel from the mouth to the anus. Symptoms include abdominal pain, diarrhoea, pyrexia and weight loss. Extra-intestinal manifestations include arthritis, uveitis, fatigue, anaemia and rashes including pyoderma gangrenosum and erythema nodosum.Other options:- Anorexia nervosa is an important diagnosis to consider. There are no indicators in the description that she has a fear of gaining weight or a strong desire to be thin.- Diabetic ketoacidosis is incorrect because there is no polydipsia or polyuria. A patient in DKA is more likely to present with vomiting and not diarrhoea.- Recurrent aphthous stomatitis is not a correct answer because it does not explain all of the symptoms described, only the mouth ulcers.- Ulcerative colitis (UC) is also incorrect. UC is a form of inflammatory bowel disease that causes inflammation in the colon. The main symptom is bloody stools, which is not mentioned as a feature in history.

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

Syphilis is an infectious venereal disease caused by the spirochete Treponema pallidum. Syphilis is transmissible by sexual contact with infectious lesions, from mother to foetus in utero, via blood product transfusion, and occasionally through breaks in the skin that come into contact with infectious lesions. If untreated, it progresses through 4 stages: primary, secondary, latent, and tertiary. Primary and secondary syphilis are easy to treat with a penicillin injection. Penicillin is one of the most widely used antibiotics and is usually effective in treating syphilis. People who are allergic to penicillin will likely be treated with a different antibiotic, such as:doxycyclineazithromycinceftriaxone

Pubic lice are commonly referred to as ‘crabs’ because of their short, broad body (about 1 mm), and large front claws. Pubic lice infestation is diagnosed by finding a “crab” louse or eggs on hair in the pubic region or, less commonly, elsewhere on the body (eyebrows, eyelashes, beard, moustache, armpit, perianal area, groin, trunk, scalp). Although pubic lice and nits can be large enough to be seen with the naked eye, a magnifying lens may be necessary to find lice or eggs.Pubic lice are transmitted from person to person most-commonly via sexual contact, although fomites (bedding, clothing) may play a minor role in their transmission.

Unprotected anal or vaginal sexual intercourse with an infected individual is by far the most common (95%) route by which HIV is transmitted. Other options:- Blood transfusion is an extremely rare cause of HIV transmission in the UK. – While HIV can be transmitted from mother to baby either during birth or via breastfeeding, the transmission rate is only 5 – 20%.- Sharing contaminated needles does put individuals at risk of getting HIV, although public health measures are in place to reduce this risk. – Although HIV can be transmitted via this route, it is around ten times less likely to result in transmission than unprotected anal or vaginal intercourse with an infected individual.

In the first few years of life the developing sensory inputs are important. Hearing is essential for speech and language development and may be delayed when a child cannot hear. Therefore any child with a family history of hereditary deafness should be screened. From about 4-6months babies are able to laugh and babble when excited or unhappy. By the age of 9 months the child should be able to bring together groups of same sound syllables and be able to say one or two words by the 1st birthday. If a child is unable to babble by 10-12 years, it may indicate hearing impairment. By the age of 2 a child should be able to speak in 1 or 2 word phrases and often repeats phrases used by others, known as Echolalia.

Haemophilia A and haemophilia B are inherited in an X-linked recessive pattern. The genes associated with these conditions are located on the X chromosome, which is one of the two sex chromosomes. In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition.

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.

Among the options provided, a 1-year-old child will be able to understand object permanence e.g. understands that objects continue to exist even when they can’t be seen, e.g. looking for a fallen toy.At the age of 1 year, children should have developed an accurate pincer grip and be able to see and co-ordinate and manipulate fairly small objects such as a raisin.Gross motor development varies, but the average 1-year-old should be able to stand and cruise around furniture or walk with their hands held but not necessarily walk unaided.Drinking from a cup will become established at around 15 months and scribbling at 18 months.

Precocious puberty is the development of secondary sexual characteristics before the age of 8 in females, and 9 in males. The first sign of early puberty in females is breast enlargement, followed by the appearance of pubic and axillary hair, and finally menarche, 2-3 years after the onset of thelarche. Precocious puberty is caused by the premature activation of the hypothalamic-pituitary-gonadal axis where FSH and LH levels are raised. Less common is the gonadotrophin independent form, which is due to excess sex hormones, but low FSH and LH levels.

Erythema nodosum (EN) is an acute, nodular, erythematous eruption that usually is limited to the extensor aspects of the lower legs. Chronic or recurrent erythema nodosum is rare but may occur.Currently, the most common cause of erythema nodosum is streptococcal infection in children and streptococcal infection and sarcoidosis in adults.The eruptive phase of erythema nodosum begins with flulike symptoms of fever and generalized aching. Arthralgia may occur and precedes the eruption or appears during the eruptive phase. Most lesions in infection-induced erythema nodosum heal within 7 weeks, but active disease may last up to 18 weeks. In contrast, 30% of idiopathic erythema nodosum cases may last more than 6 months. Febrile illness with dermatologic findings includes abrupt onset of illness with initial fever, followed by a painful rash within 1-2 days.

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, the 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.

Umbilical vein catheterization utilizes the exposed umbilical stump in a neonate as a site for emergency central venous access up to 14 days old. Umbilical vein catheterization can provide a safe and effective route for intravenous delivery of medications and fluids during resuscitation.The indication for umbilical vein catheterization is when there is a need for IV access in a neonate for resuscitation, transfusions, or short-term venous access when otherwise unobtainable.

The CSF picture in bacterial meningitis has the following characteristics: several polymorphs, cells, protein that is maximum 5g/l, a few lymphocytes and glucose that accounts for the two thirds of the blood level.

Skin conditions resulting from excessive epidermal proliferation or inflammation, leading to a production of excessive scales, are referred to as papulosquamous disorders. These disorders can be generalized and localized. Localized causes of scaly lesions include tinea corporis, tinea cruris, tinea pedis, seborrheic dermatitis, psoriasis, pityriasis Versicolor, pityriasis alba, DLE, ichthyosis including Netherton syndrome (a severe form of ichthyosis which is autosomal recessive), and pellagra. Generalized causes include guttate psoriasis and pityriasis rosacea. Hand, foot, and mouth disease is a contagious viral illness that causes blisters in the mouth and on the extremities.

Iron deficiency anaemia has the following laboratory characteristics: low haemoglobin, a low serum iron, a low serum ferritin, a low transferrin saturation, and a high total iron-binding capacity.

Clinical signs of early pregnancy-Amenorrhoea-Nausea and vomiting -Breast enlargement and tenderness -Hyperpigmentation of the areola and formation of linea nigra: Most likely due to increased levels of melanocyte-stimulating hormone produced by the placenta -Increased urinary frequency-Fatigue-Cravings for or aversions to certain foods-Abdominal bloating and constipation

This patient has pulmonary renal syndrome which is most commonly due to an ANCA positive vasculitis. The history of recurrent epistaxis makes Wegener’s granulomatosis the most probable diagnosis. Wegener’s granulomatosis, microscopic polyangiitis, and idiopathic pauci-immune necrotizing crescentic glomerulonephritis (NCGN) are strongly associated with antineutrophil cytoplasmic autoantibodies (ANCAs) directed against either proteinase 3 (anti-PR3) or myeloperoxidase (anti-MPO).

Haemophilia B (also known as Christmas disease) is due to a deficiency in factor IX. Haemophilia A is due to a deficiency in factor VIII.

Haemolytic uremic syndrome belongs to a heterogeneous group of disorders characterized by a triad of thrombocytopenia, microangiopathic haemolytic anaemia, and acute kidney injury. It is one of the most common causes of renal injury in children. The clinical findings are due to thrombotic microangiopathy, which leads to arterioles and capillary wall thickening along with endothelial swelling and detachment. The significant laboratory findings include increased white cell count, raised serum urea and creatinine, increased serum LDH, decreased platelet count, haematuria, and proteinuria.

Congenital duodenal atresia is one of the more common intestinal anomalies treated by paediatric surgeons, occurring 1 in 2500-5000 live births. In 25-40% of cases, the anomaly is encountered in an infant with trisomy 21 (Down syndrome).Presenting symptoms and signs are the results of high intestinal obstruction. Duodenal atresia is typically characterized by the onset of vomiting within hours of birth. While vomitus is most often bilious, it may be nonbilious because 15% of defects occur proximal to the ampulla of Vater. Occasionally, infants with duodenal stenosis escape detection of an abnormality and proceed into childhood or, rarely, into adulthood before a partial obstruction is noted. Nevertheless, one should assume any child with bilious vomiting has a proximal GI obstruction until proven otherwise, and further workup should be begun expeditiously.Once delivered, an infant with duodenal atresia typically has a scaphoid abdomen. One may occasionally note epigastric fullness from dilation of the stomach and proximal duodenum. Passing meconium within the first 24 hours of life is not usually altered. Dehydration, weight loss, and electrolyte imbalance soon follow unless fluid and electrolyte losses are adequately replaced. If intravenous (IV) hydration is not begun, a hypokalaemic/hypochloraemic metabolic alkalosis with paradoxical aciduria develops, as with other high GI obstruction. An orogastric (OG) tube in an infant with suspected duodenal obstruction typically yields a significant amount of bile-stained fluid.

Most cases of Trisomy 18, also called Edwards syndrome, are not inherited but occur as random events during the formation of eggs and sperm. An error in cell division called nondisjunction results in a reproductive cell with an abnormal number of chromosomes. For example, an egg or sperm cell may gain an extra copy of chromosome 18. If one of these atypical reproductive cells contributes to the genetic makeup of a child, the child will have an extra chromosome 18 in each of the body’s cells.Mosaic trisomy 18 is also not inherited. It occurs as a random event during cell division early in embryonic development. As a result, some of the body’s cells have the usual two copies of chromosome 18, and other cells have three copies of this chromosome.Partial trisomy 18 can be inherited. An unaffected person can carry a rearrangement of genetic material between chromosome 18 and another chromosome. This rearrangement is called a balanced translocation because there is no extra material from chromosome 18. Although they do not have signs of trisomy 18, people who carry this type of balanced translocation are at an increased risk of having children with the condition.Canavan disease is a type of leukodystrophy and a degenerative disorder that causes progressive damage to nerve cells in the brain. It is inherited in an autosomal recessive manner.Cystic Fibrosis is the most common lethal recessive disease of white people, with a carrier frequency of 1:25 and is inherited in an autosomal recessive manner.Galactosaemic is autosomal recessive and due to mutations in the GALT gene.Phenylketonuria is the most common inborn error of metabolism in the UK with an incidence of 1:10,000 and a carrier rate of 1:50.

Hereditary diseases follow specific inheritance patterns according to the type of gene involved. Mutations in the genes which are on the sex chromosome, chromosome X are called X-linked diseases. X-linked recessive conditions result when both the copies of X-chromosomes are defective, which happens in the case of females since males have only one X- chromosome. Thus, these conditions are more common among males, and examples include colour blindness, haemophilia, Lesch-Nyhan syndrome, and hunter’s syndrome, etc. Hunter’s syndrome is a type of lysosomal storage disease which is also known as mucopolysaccharidosis II. Vitamin D resistant rickets is a X-linked dominant disease. Neurofibromatosis type 1 and 2 are autosomal dominant conditions while Wilson’s disease is autosomal recessive.

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.