Allergy And Immunology Flashcards
A 4-year-old boy has been brought into accident and emergency with breathing problems. He is assessed by the paediatric team and found to have inspiratory and expiratory stridor, audible wheeze, lip and tongue swelling, and an urticarial rash on his trunk and abdomen. His heart rate is 167 bpm and his respiratory rate is 40, BP 90/45 mmHg. What is the single most important management step?
A. Do not examine his throat as this may distress him
B. Give a normal saline fluid bolus
C. Give IV adrenaline 0.1 mg/kg of 1:10 000
D. Give IM adrenaline 0.01 mg/kg of 1:1000
E. Mobilize the paediatric anaesthetist as his airway is compromised
D. Give IM adrenaline 0.01 mg/kg of 1:1000
1 DHe has clear signs of anaphylaxis, with involvement of cardiovascular and respiratory systems. He is hypotensive and tachycardic and although a fluid bolus is required (B), adrenaline IM (D) is the most important initial step. Adrenaline is a catecholamine which in anaphylaxis should be given IM and not IV (C) (this is in contrast to a cardiac arrest protocol where it is given IV or through an endotracheal tube). IM adrenaline will cause vasoconstriction, bronchodilation and temporarily slow the anaphylactic process, which is histamine driven. A paediatric anaesthetist will also be required to assess and manage airway obstruction due to the enlarged tongue and upper airway soft tissues (E); however adrenaline must be given first to buy time for them to arrive. The effects of adrenaline are short lived and continued assessment is necessary. Once the reaction has settled there is a biphasic response, meaning the child may have a second reaction despite no contact with the allergen 6–12 hours later. Not examining the throat (A) refers to upper airway obstruction caused by epiglottitis or bacterial tracheitis and is not appropriate here.
A 12-year-old girl with a history of discitis in her lumbar spine was admitted following investigation at her tertiary centre. She was started on IV benzylpenicillin and clindamycin. She received 24 hours of medication and a rash appeared on her trunk and arms. There were discrete red lesions which outlined a central target lesion. They were non-blanching and itchy. What is the most likely diagnosis?
A. Erythema migrans
B. Erythema toxicum
C. Erythema marginatum
D. Erythema nodosum
E. Erythema multiforme
E. Erythema multiforme
2 E Erythema multiforme (E) is the rash described with target lesions with a surrounding red ring. The causes are numerous including: drugs (e.g. penicillin), infection (e.g. atypical pneumonia) or idiopathic. Erythema nodosum (D) can have similar categories of causes including drugs (e.g. sulphonamides), infection (e.g. streptococcal spp.), autoimmune and malignancy, but inflammatory bowel disease is also a well-known cause. Erythema migrans (A) is a rash due to Lyme’s disease. Erythema toxicum (B) is a benign rash (characteristically seen as small pustules or vescicles surrounded by an erythematous area) seen in newborns in the first 2 weeks of life. Erythema marginatum (C) in seen in rheumatic fever along with the other cardinal signs which include carditis, arthralgia, subcutaneous nodules and Sydenham’s chorea.
A 3-year-old boy is admitted to the children’s ward. He has been isolated in a cubicle as he is at risk of infections. He is awaiting a bone marrow transplant and has a brother with the same condition. His mother tells you they both have SCID. What are the likely immune function test results in SCID?
A. Normal B cells, normal T cells, normal immunoglobulins
B. Low B cells, low T cells, low immunoglobulins
C. Normal B cells, normal T cells, high immunoglobulin M subsets
D. Low B cells, normal T cells, low immunoglobulins
E. Normal B cells, low T cells, normal immunoglobulins
B. Low B cells, low T cells, low immunoglobulins
3 B SCID is a group of disorders caused by B and T cell dysfunction. SCID affects both B and T lymphocyte cell lines; therefore only (B) can be correct. Low B cell numbers result in reduced immunoglobulin production. (A) would be the result in an immunocompetent host. (C) may be due to hyper IgM syndrome, which is due to a defect in the CD40 ligand, resulting in defective class switching and T cell function and recurrent infections. (D) may be suggestive of Bruton’s agammaglobulinaemia, where lack of B cells results in low immunoglobulins and predisposition to respiratory and central nervous system (CNS) infections. (E) may result from thymic hypoplasia or absence as the T cells alone are affected with normal B cells and immunoglobulins; this may be associated with DiGeorge’s syndrome.
A 3-week-old baby attends accident and emergency with bloody diarrhoea. Mum says he has been having diarrhoea for the past 2 days since she started using formula milk. He was previously breastfed and mum was not having any dairy products due to lactose intolerance. He also has eczema on his cheeks and a strong family history or asthma and eczema. Mum is concerned that he may be allergic to milk too. What is the most likely diagnosis?
A. Lactose intolerance
B. Gastroenteritis
C. Cow’s milk protein intolerance
D. Fructose intolerance
E. Galactosaemia
C. Cow’s milk protein intolerance
4 CCow’s milk protein intolerance (C) is an allergic reaction secondary to allergens in cow’s milk. Babies may present with diarrhoea on introduction of cow’s milk based formula or breast milk if the mother takes dairy products. Cow’s milk protein intolerance may also be associated with eczema, commonly on the face. Lactose intolerance (A) can present similarly, but the congenital form is extremely rare (due to absolute lactase deficiency at the brush border) though lactase expression starts to reduce from 2 years of age in most people. Fructose intolerance (D) is a rare metabolic condition presenting with vomiting, hypoglycaemia, failure to thrive, hepatomegaly, jaundice, renal complications and severe metabolic acidosis. Gastroenteritis (B) should be considered, but in the presence of vomiting and fever which are absent here. Galactosaemia (E) is due to galactose-1-phosphate uridyl transferase deficiency, which can present with metabolic disturbances, sepsis, vomiting and collapse.
A 2-year-old child is brought to cardiology clinic due to a heart murmur heard by the GP after an examination when she was recently unwell. She was born at 40 weeks by normal vaginal delivery but was noted to have a cleft palate at birth. She was kept in hospital for establishment of feeding but during this time she had a seizure, noted later to be because her calcium was low. You hear a harsh, grade 3/6 pansystolic murmur, loudest at the left lower sternal edge, consistent with a ventral septal defect (VSD) as seen on echocardiogram. With this history and current examination finding, you wish to exclude DiGeorge’s syndrome. What is the best diagnostic test?
A. Karyotype
B. FISH (fluorescence in situ hybridization)
C. ELISA (enzyme-linked immunosorbent assay)
D. Geneticist review and diagnosis
E. Identification of specific mutation
B. FISH (fluorescence in situ hybridization)
5 B DiGeorge syndrome is due to a microdeletion on chromosome 22q11.2. It manifests as a collection of features including cleft palate, aortic arch and other cardiac abnormalities, thymic hypoplasia, typical facial features and hypocalcaemia. Microdeletions are best detected with FISH (B). Abnormalities in chromosome number or translocations can be seen with karyotyping (A) and known mutations can be identified (E), but since DiGeorge’s syndrome is not due to a specific mutation this is not appropriate. ELISA (C) is used for the identification of known proteins, e.g. autoantibodies, bacterial/viral detection. A geneticist review (D) may be helpful, particularly for planning of further pregnancies.
A 13-year-old girl is on the ward having a bone marrow transplant for acute leukaemia. She is noted to be profoundly anaemic with haemoglobin 5.9 g/dL and she is due to receive a transfusion of one unit of red blood cells. You are called to see her 5 minutes after starting the transfusion. She has come out in a rash, is looking frightened, with a heart rate of 120 bpm and respiratory rate of 30. As you arrive, you can see she has swollen lips and tongue and her blood pressure is measured as 90/45 mmHg. What is the best initial management step?
A. Repeat a full set of observations as it is likely to be anxiety resulting in the abnormal heart rate, respiratory rate and blood pressure. If still abnormal, stop transfusion
B. Stop the transfusion and return the unit of blood to blood bank
C. Stop the transfusion, take down the giving set, give IM adrenaline immediately
D. Give IM adrenaline, stop the transfusion, take down the giving set
E. Stop the transfusion, give IM adrenaline immediately and restart if the reaction settles
C. Stop the transfusion, take down the giving set, give IM adrenaline immediately
6 CThere are clear transfusion guidelines which you should be familiar with – see Handbook of Transfusion Medicine from the UK Blood Transfusion Services. There are multiple transfusion reactions, but this is an allergic/ anaphylactic reaction. The blood should be stopped and taken down first (removal of the allergen); therefore (A) and (D) are incorrect. The patient is in anaphylactic shock and therefore should be given IM adrenaline (C), not (B). This unit of blood should most certainly not be restarted (E) and should be returned to the blood bank for further analysis.
A couple are referred to a geneticist as they are planning on having their first child. There is a history of Wiskott–Aldrich syndrome on the woman’s side. The woman’s father and great grandfather have the condition (eczema, thrombocytopenia, recurrent infection) but she is unaffected. There is no history of the condition in the man’s family. What is the risk of having the condition if the child is a boy or a girl respectively?
A. Boy: 1/4; Girl: 1/4
B. Boy: 1/2; Girl: 0
C. Boy: 0; Girl: 0
D. Boy: 0; Girl: 1/2
E. Boy: 1; Girl: 0
B. Boy: 1/2; Girl: 0
7 B Wiskott–Aldrich syndrome is an X-linked condition due to defects in the WASp gene, affecting cell cytosketeton protein actin and associated with the above features. It presents with this triad in approximately one-third of cases, with the other having predominantly haematological complications such as petechiae and bruising. The woman’s father has the condition and therefore she is a carrier. The risk of her having a son with the condition is 1/2 and a daughter is 0 (she can only be a carrier) (B). (A) is based on an autosomal recessive condition, with both parents as carriers, and (C) occurs if the mother is a carrier and the father is not affected. (E) is based on the condition being X-linked dominant, but then the mother should have been affected.
A 4-year-old boy with severe ezcema is brought to accident and emergency by his mother. His skin has been worse recently since the weather has become colder. He is scratching a lot more and now is very miserable and has a temperature of 38.6°C today. On examination of his skin he has multiple areas of erythematous, excoriated lesions on his elbow and knee flexures as well as his trunk and back. In addition they are hot, tender and slightly swollen with areas of broken skin. There are also some yellow fluid-filled vesicles on some of these lesions. You send some blood tests and commence him on IV flucloxacillin and aciclovir. Which are the two most likely organisms that can complicate eczema?
A. Gram-positive cocci and herpes simplex virus
B. Gram-negative cocci and herpes simplex virus
C. Gram-positive cocci and varicella zoster
D. Gram-negative bacilli and herpes zoster
E. Gram-positive bacilli and herpes simplex
A. Gram-positive cocci and herpes simplex virus
8 ACellulitis (bacterial superinfection) and eczema herpeticum (herpes simplex virus infection) are the two important complications of eczema. Gram-positive cocci (Staphylococcus spp. and Streptococcus spp.) are responsible for cellulitis. These occur due to breakage of the skin barrier in the eczematous areas allowing entry of bacterial into an already inflamed epidermis and dermis. These require aggressive treatment to prevent spread of the organisms into the blood. (B) is not correct as Gram-negative cocci (Neisseria meningitidis and N.gonorrhoeae) do not produce skin infections. Varicella zoster is the causative organism for chicken pox, and reactivation of the virus which lays dormant in the dorsal root ganglion is known as herpes zoster (shingles). They do not specifically cause infection of eczematous skin; therefore (C) and (D) are incorrect. (E) is incorrect as Gram-positive bacilli such as Clostridium spp., Bacillus spp. or Listeria spp. do not typically cause primary skin infections.
A 3-year-old boy has been admitted to hospital with a right-sided pneumonia and pleural effusion. The pleural fluid grew Gram-positive cocci. He is on IV ceftriaxone, oral azithromycin and has a chest drain in situ. On further questioning of Richard’s mother, you establish that he has had multiple chest infections since he was born (in the UK). He has been admitted three times before and also had a sinus wash out following an episode of sinusitis. He has no cardiac anomalies or dysmorphism. His mother also tells you about his older brother, who sadly died of meningitis aged 6 years old. He too had ‘more than his fair share of infections’. The two brothers had different fathers but his mother is HIV negative. What is the most likely underlying immunodeficiency in this family?
A. DiGeorge’s syndrome
B. Complement deficiency
C. X-linked agammaglobulinaemia
D. Subacute combined immunodeficiency disorder (SCID)
E. HIV
C. X-linked agammaglobulinaemia
9 CThis boy presents with recurrent respiratory tract infections and although these are common in childhood, the frequency, severity and causative organisms are important to consider. It is difficult to clearly differentiate immunodeficiencies, but it is a balance of probabilities as to the most likely cause. He is unlikely to have SCID (D) as this usually presents earlier in life and may have been fatal by 3 years of age if undiagnosed. Their mother is HIV negative which means vertical transmission of HIV is excluded and he is unlikely to have acquired HIV (E). He is lacking in other features which are suggestive of DiGeorge’s syndrome (A) (cleft palate, midfacial hypoplasia, cardiac anomalies (including Tetralogy of Fallot), VSD) and hypocalcaemia. Complement deficiency (B) can present in a spectrum of phenotypic characteristics, but commonly in meningococcal infections. The fact that two brothers both have the propensity to infections should raise the suspicion of an X-linked condition (irrespective of the paternity of the brothers). The lack of B cells, and therefore immunoglobulins, predisposes to bacterial infection, particularly of the respiratory tract but also the CNS, making (C) the most likely.
You are in immunology clinic and the first patient is a 2-year-old boy who has a complement deficiency. You know this involves a cascade of proteins involved with innate immunity but are unsure about the manifestations in children. The professor of immunology asks you which organism is this child at risk of being infected with. He gives you a clue by telling you the child has a late complement deficiency, meaning C5-C9. What is the most likely causative organism that infects these children?
A. Streptococcus pneumoniae
B. Neisseria meningitidis
C. Haemophilus influenzae
D. Mycobacterium tuberculosis
E. Pneumocystis jiroveci
B. Neisseria meningitidis
10 B The complement pathway is important in detecting and eradicating these organisms early on and, without effective complement systems, overwhelming infection may develop. The complement cascade involves a series of proteins which can opsonize and create and insert a membrane attack complex into the organism, which aims to eradicate it. Deficiencies along the pathway have been noted: protein C3 resulting in recurrent pyogenic infection, protein C1, C2 and C4 associated with autoimmunity and proteins C5–9 with a risk of getting infections with N. meningitidis (B). Children with sickle cell disease (functional asplenia) or other children without a functioning spleen are at risk of infection with encapsulated organisms such as (A) or (C). Patients who are immunocompromised (secondary to HIV or immunosuppressive therapy, e.g. steroids or chemotherapy), are at risk of (D) or (E).
