EM A n I

Question 1

rash shown in the picture is urticaria. Urticaria following use of a drug, especially penicillin, is often due to

Answer 1

IgE-mediated reactions.
IgE is fixed to mast cells and with cross-linking by a specific antigen, potent vasodilator substances like histamine and leukotrienes are released. The result is urticaria, swelling and edema in the epidermis. Angioedema, edema and swelling at the dermoepidermal junction and subcutaneous tissues, results from the same mechanism. This type of reaction is often called a Type I hypersensitivity.

Question 2

Type II hypersensitivity is mediated by

Answer 2

cytotoxic antibodies. These antibodies are formed in response to an environmental antigen or a self-antigen. Upon subsequent exposure, the antigen may attach to a cell and result in binding of the antibody to the attached antigen. Complement activation begins, resulting in cell damage or destruction. An example of a Type II mediated response is a drug-induced hemolytic anemia.

Question 3

These immune complexes lodge in small vessels and tissues, primarily skin, joints, and lung. This activates the serum complement cascade, releasing enzymes and prostaglandins. Serum sickness is the classic example of a

Answer 3

Type III hypersensitivity. An IgG-mediated response occurs mostly with injected antigens or occasionally with ingested substances. It is also called a Type III hypersensitivity and results from antigen-antibody immune complex formation.

Question 4

A deficiency of C1 esterase inhibitor results in

Answer 4

hereditary angioedema. This is an autosomal dominant condition. The deficiency leads to spontaneous complement activation and can have life-threatening consequences due to laryngeal edema. The diagnosis is made by measurement of C1 esterase inhibitor levels.

Question 5

A cell-mediated reaction (Type IV hypersensitivity) does not involve antibody; rather, it involves

Answer 5

T-lymphocytes. The cell has a specific receptor for an antigen, and after the initial exposure, the cells will proliferate and change into natural killer cells and/or recruiting cells. Examples of this type of hypersensitivity include graft-versus-host response and tuberculin skin tests.

Question 6

Treatment of immunocompromised patients with primary varicella infections due to the high risk of disseminated disease and complications from infection.

Answer 6

High doses of IV acyclovir (500 mg/m2 IV every 8 hours)

Question 7

To prevent primary varicella infection in susceptible patients who have been exposed to the virus,

Answer 7

varicella zoster immune globulin (VZIG) needs to be administered within 96 hours of exposure and sooner, if possible, for maximum effectiveness.

Question 8

Varicella vaccination should not be administered to

Answer 8

persons receiving high dose systemic steroids and should not be given concurrently with VZIG

Question 9

13-year old child has recurrent pulmonary infections. All childhood immunizations have been received as scheduled. Results of laboratory studies, including blood counts, plasma immunoglobulins, and sweat test, are within normal limits. Intradermal injection of 1:5 dilution of tetanus toxoid does not lead to an erythematous, indurated lesion during the next 3 days.

Answer 9

Impaired T cell function which needs further investigation

Question 10

Recurrent pulmonary infections warrant thorough laboratory investigation, including blood counts, sedimentation rate, plasma immunoglobulins, and sweat test. In addition, skin test responses are helpful in

Answer 10

assessing T lymphocyte function.

Question 11

Delayed hypersensitivity, a type IV hypersensitivity reaction, depends on the

Answer 11

the intact functioning of T cells. A variety of antigens, to which most older children and adults have been exposed, can be used for testing: purified protein derivative (PPD), histoplasmin, candidin (most people have been exposed to this yeast antigen), and mumps antigen. Intradermal injection of tetanus toxoid is particularly useful. Positive test is indicated by an erythematous, indurated lesion that peaks after 48 hours.

Question 12

Patients with complement deficiencies have

Answer 12

normal white blood cell and neutrophil counts and function.

Question 13

Deficiency of the membrane attack complex or properdin, which stabilizes the alternative C3 convertase, tend to manifest in

Answer 13

recurrent Neisseria infections.

Question 14

teenager shows typical symptoms of allergic rhinitis, a type I immediate hypersensitivity reaction. IgE is only 0.004% of total serum immunoglobulins, but binds with high affinity to mast cells and basophils through a site in the Fc region. In the phase of sensitization, allergen specific IgE binds to high-affinity Fc receptors on mast cells and basophils. Production of IgE antibodies is driven by the production of IL-4 by helper CD4 T cells (TH2 cells). The symptoms are caused by

Answer 14

a re-exposure release of active mediators, following antigens reacting with mast cell bound IgE. Antibody reaction with cell-bound antigen is a type II hypersensitivity reaction. Immune-complex disease is a local tissue damage caused by antigen-antibody complexes. Hypersensitivity disorder, caused by the presence of persistent antigen within macrophages, is a typical type IV delayed hypersensitivity reaction.

Question 15

Antihistamines, like diphenhydramine,

Answer 15

block histamine mediator binding to target tissue.

Question 16

Corticosteroids

Answer 16

stabilize granules and cell membranes. Particularly, topical corticosteroids are highly effective and rapidly metabolized. They have minimal systemic effect.

Question 17

Cromolyn sodium, a highly effective preventive pharmacologic agent, acts through

Answer 17

inhibiting calcium influx.

Question 18

inhibits phosphodiesterase conversion of cAMP to AMP and also increases the intracellular amount of cAMP.

Answer 18

theophylline

Question 19

stimulates adenylate cyclase and, therefore, increases the conversion of ATP to cAMP.

Answer 19

Epinephrine

Question 20

_______consists of thymic hypoplasia and hypoparathyroidism. There will be a T-cell deficiency because of the thymic hypoplasia, which would result in viral and fungal infections.

Answer 20

DiGeorge syndrome

Question 21

_______is characterized by a defect in both cellular and humoral immunity. There would be a decrease in the lymphocyte count.

Answer 21

Severe combined immunodeficiency

Question 22

______ would present with a low level of immunoglobulins.

Answer 22

X-linked agammaglobulinemia is also called Bruton’s agammaglobulinemia. X-linked agammaglobulinemia

Question 23

Characteristics of _____ include eczema, infections, small platelet size, and a low platelet count. It is X-linked recessive.

Answer 23

Wiskott-Aldrich syndrome

Question 24

chronic diarrhea, failure to thrive, and cutaneous manifestations of vesiculobullous eczematous symmetrical eruptions in the perioral areas, cheeks, knees and elbows, and perineal regions, with delayed milestones and growth retardation. stomatitis, glossitis, paronychia, and dystrophy of nails.

Answer 24

Acrodermatitis enteropathica is an autosomal recessive disorder caused by inability to absorb sufficient zinc from the diet. The genetic defect is in the intestinal zinc specific transporter gene. Genetic mutation is on chromosome 8q24. Initial signs and symptoms appear during the first few months of life especially after weaning from breast to top milk. The dermatitis is mainly periorificial (around the natural orifices) and acral (over the limbs).

Question 25

Acrodermatitis enteropathica.
Oral zinc therapy is the treatment of choice. For infants 50mgm of zinc sulphate, acetate or gluconate daily, and 150mgm/day for older children is adequate. Signs and symptoms are rapidly abolished after zinc therapy.

Answer 25

t is diagnosed by low plasma zinc concentration. The wide variety of manifestations are perhaps due to the fact that zinc plays an important role in numerous metabolic pathways including those of proteins, copper, essential fatty acids, and prostaglandins.

Question 26

Urticaria lasting fewer than 6 weeks is considered acute, and almost 60% of cases result from a proven or probable viral infection. A history will reveal recent nonspecific symptoms such as fever, sore throat, dysuria, or a sick contact. Treatment consists of

Answer 26

reassurance and symptomatic care (local and oral antihistamines).

Question 27

Urticaria lasting longer than 6 weeks is termed chronic and has an average duration of 12 to 36 months. Chronic urticaria (CU) is less prevalent than acute urticaria for all ages. Recent studies show that 30% to 50% of cases are autoimmune, involving circulating autoantibodies that lead to degranulation and mediator release from mast cells and basophils. Serum or skin IgE food testing is thus not recommended; although, an autologous serum skin test (ASST) may be helpful. The presence of a 1.5 mm or greater wheal than the control is considered positive. Treatment

Answer 27

Non-sedating second-generation H1 antihistamines are considered first line therapy. First-generation sedating H1 antihistamine can be used as a ‘rescue’ medication for ‘breakthrough’ symptoms or severe cases .

Question 28

recurrent bacterial infections of the skin, mouth, and respiratory tract, There is delayed detachment of the umbilical cord. The leukocyte count is elevated. If the neutrophil count is persistently elevated in the absence of any sign of infection, then a

Answer 28

leukocyte adhesion defect should be suspected.

Question 29

______ anomaly arises due to defects in embryogenesis of the 3rd and 4th pharyngeal pouches; it is characterized by atypical facies (hypertelorism antimongoloid slant, low set ears, micrognathia, short philtrum of the upper lip, bifid uvula) hypocalcemic tetany, an aortic arch anomaly, and an absent thymus. In addition, these children have a variable T-cell defect, resulting in an increased susceptibility to infection.

Answer 29

DiGeorge

Question 30

SCID can be detected at birth by the identification of ______?
Infants commonly present with recurrent or persistent diarrhea, pneumonia, otitis media, sepsis, and skin infections. Growth is normal initially, but marked wasting ensues when diarrhea and infections begin. Infections due to opportunistic organisms, including candida albicans, Pneumocystis jiroveci, respiratory syncytial virus (RSV), rotavirus, cytomegalovirus(CMV), Epstein-Barr virus, varicella zoster, measles, and MMR-vaccine virus, can be fatal.

Answer 30

lymphopenia (absolute lymphocyte count

Question 31

____ presents as severe and repetitive vomiting, which is sometimes accompagnied by diarrhea, and it may lead to dehydration and lethargy or failure to thrive

Answer 31

Food Protein-Induced Enterocolitis Syndrome (FPIES) is also a non-IgE-mediated food allergy; it presents in infancy and is caused by cow milk, soy formulas, as well as solid foods.

Question 32

2-month-old female infant presents after passing small amounts of bloody-appearing stool 3 times. Her bowel movements have not been hard or dry, and she has otherwise been well. She was a full-term infant born by Cesarean section due to breech presentation. She transitioned well, and the mother is almost exclusively breastfeeding, with occasional formula 1 to 2 times a week. She does have some mild reflux, but it has been gradually improving with reflux precautions, and she has been gaining weight well. There is no significant family history of allergic disease.

Answer 32

a food protein-induced proctitis/colitis and enteropathy in infancy, causing bloody stools.
This condition appears to be induced by food protein in the absence of IgE anti-food antibodies. An orally ingested protein induces an inflammatory response that is limited to the rectum and distal sigmoid colon. 50% of infants studied were breastfed and determined to have symptoms attributed to maternal ingestion of cow’s milk followed by egg, corn, and soy. These infants are generally healthy, but they pass blood tinged stools and mucus. The condition typically presents between 2 and 8 weeks of age. With complete elimination of the offending protein from the mother’s diet, clinical bleeding clears within 3 days.