Chapter 15 - Allergy & Immunology

Question 1

What are the presenting signs of anaphylaxis?

Answer 1

by definition, symptoms must appear within 30 minutes of exposure

• skin: pruritis, flushing, urticarial, angioedema
• respiratory: dyspnea and wheezing
• GI: n/v/d
• cardiovascular: hypotension ranging form mild to shock

Question 2

Allergic Rhinitis

Answer 2

• an IgE-mediated inflammatory response in the nasal mucosa to inhaled antigens
• seasonal is typically in response to tree, grass, or weed pollens; perennial to indoor allergens like dust mites and animal dander
• may present with sneezing, nasal congestion, rhinorrhea, nasal itching, pale nasal mucosa, allergic shiners, dennie’s lines, or allergic salute
• skin testing is the most effective method for diagnosing allergic rhinitis, but total IgE concentration and nasal smear cytology can also be used
• treatment involves avoidance, medications (intranasal steroids, antihistamines, intranasal cromolyn sodium, and decongestants), and immunotherapy

Question 3

What are allergic shiners, Dennie’s lines, and the allergic salute?

Answer 3

• allergic shiner: dark circles under the eyes caused by venous congestion in those with allergic rhinitis
• Dennie’s lines: crease under the eyes resulting from chronic edema
• allergic salute: patients use the palm of the hand to elevate the tip of the nose and relieve itching

Question 4

What is nasal smear cytology?

Answer 4

• a way of differentiating allergic rhinitis from other conditions
• more than 10% eosinophils suggests allergic rhinitis whereas predominately PMNs suggests an infectious cause

Question 5

What avoidance precautions are recommended for patients with severe rhinitis?

Answer 5

• remove pets from the home or keep them outdoors
• use plastic mattress covers, remove carpets, and remove stuffed animals to reduce dust mites
• reduce humidity to inhibit growth of dust mites and mold
• avoid open windows

Question 6

What is the most effective class of drugs for controlling allergic rhinitis?

Answer 6

intranasal steroids

Question 7

Name one first-generation antihistamine and three second-generation ones.

Answer 7

• diphenhydramine

- cetirizine, fexofenadine, loratadine

Question 8

Eczema (Atopic Dermatitis)

Answer 8

• a type I hypersensitivity reaction
• the skin is overly sensitive to many stimuli, producing pruritus, leading to scratching, causing the skin to become dry and undergo lichenification (thickening)
• presentation is usually in early infancy, before age 5, and in those with a family or personal history of atopy
• presents with pruritus; an acute erythematous, weeping, crusting rash, often complicated by secondary bacterial or viral infection with S. aureus or HSV; and a chronic lichenification with pigmentary changes
• typically begins on the face and the migrates to the antecubital fossa, affecting flexor surfaces more commonly than extensors
• managed with avoidance of triggers, low-to-medium-potency steroids, and antihistamines; patients should bath in tepid water, be blotted dry after, and apply skin lubricants

Question 9

Which foods most commonly cause allergic reactions?

Answer 9

egg, milk, peanut, soy, wheat, fish

Question 10

How does food allergy present and how is it diagnosed?

Answer 10

• presents with oral symptoms of itching and swelling, GI symptoms, respiratory symptoms, atopic dermatitis, and acute urticaria
• anaphylaxis is the most severe manifestation
• diagnosed based on a careful history, skin testing, radioallergosorbent tests (looking for serum IgE antibodies to specific food antigens), and provocative oral food challenge

Question 11

Chronic Urticaria

Answer 11

• a rash lasting more than 6 months
• described as circumscribed, raised, migratory areas of edema that are almost always pruritic
• may be idiopathic or associated with malignancy, SLE, RA, IgG antibodies to IgE receptors, and thyroid disease
• best treated with antihistamines and further evaluation for underlying systemic disease

Question 12

Which components of the immune system are considered innate?

Answer 12

• phagocytic cells
• NK cells
• TLRs
• mannose-binding protein
• the alternative pathway of complement

Question 13

Serum Sickness

Answer 13

• a type III hypersensitivity in which antibodies to foreign proteins are produced
• most cases caused by drugs acting as haptens
• presents with fever, urticaria, arthralgia, proteinuria, and lymphadenopathy 5-10 days after antigen exposure

Question 14

How does serum sickness compare to an arthus reaction?

Answer 14

• both are type III hypersensitivities mediated by IgG
• however, an arthus reaction has a more rapid onset because it is mediated by circulating IgG (the individual has already been sensitized)
• an arthus reaction is more localized than serum sickness

Question 15

IgA Deficiency

Answer 15

• the most common immune deficiency
• defined as serum IgA concentrations < 7 mg/dL but normal levels of other isotypes
• most often asymptomatic but with increased risk of airway and GI infections, autoimmune and rheumatic disease, and atopic disease
• since IgA cannot be replaced, treatment involves management of infections and other complications

Question 16

Common Variable Immunodeficiency

Answer 16

• a B cell or helper T cell defect, which impairs B cell differentiation, resulting in hypogammaglobulinemia
• often acquired in the 20s-30s, it presents with increased risk of autoimmune disease, bronchiectasis, lymphoma, and sinopulmonary infections
• diagnosed on the basis of hypogammaglobulinemia, a decrease in plasma cells, and diminished mitogen-induced T-cell proliferation in vitro
• treated with monthly IVIG, management of infections, and treatment of chronic diarrhea with nutritional support

Question 17

Severe Combined Immunodeficiency Disease

Answer 17

• a group of inherited disorders affecting T- and B-cell functioning
• can be X-linked due to an IL-2R gamma chain mutation or autosomal recessive due to an ADA deficiency
• presents with early infection with opportunistic organisms, chronic diarrhea, and failure to thrive
• diagnosed based on severe hypogammaglobulinemia and the absence of a thymic shadow, germinal centers, and T cells
• treated with antibiotics, nutritional intervention, use of irradiated blood products to prevent GvHD, monthly IVIG, P. caring pneumonia prophylaxis with TMP-SMX
• bone marrow transplant can be curative

Question 18

Ataxia Telangiectasia

Answer 18

• autosomal recessive ATM gene mutations on chromosome 1, which impair repair of DNA double strand breaks
• presents with a triad of cerebellar defects, spider angiomas, and IgA deficiency leading to sinopulmonary infections
• patients also have a high risk of malignancy and should avoid ionizing radiation
• AFP is elevated in serum; IgA, IgG, and IgE are all reduced; and there is lymphopenia, T-cell anergy, and cerebellar atrophy
• monitor for malignancies, avoid ionizing radiation, and treat infections

Question 19

DiGeorge Syndrome

Answer 19

• a 22q11 deletion causing failure of the 3rd and 4th pharyngeal pouches to develop, leaving the thymus and parathyroids absent
• presents with cardiac anomalies, abnormal facies, thymic aplasia, cleft palate, and hypocalcemia
• there is a measurable reduction in T cells, PTH, and calcium as well as an absent thymic shadow

Question 20

Wiskott-Aldrich Syndrome

Answer 20

• an X-linked recessive mutation of the WAS gene, which impairs actin reorganization and TCR signaling
• presents with “WATER”: Wiskott Aldrich, Thrombocytopenia with small platelets, Eczema, and Recurrent Intections with encapsulated organisms
• bleeding is a major cause of mortality
• diagnosed based on thrombocytopenia, platelet size, decreased IgM, diminished antibody response to polysaccharide antigens, and anergy despite near-normal numbers of T cells
• treated with bone marrow transplant, IVIG, splenectomy, and prophylactic antibiotics or IVIG

Question 21

X-Linked Agammaglobulinemia

Answer 21

• an X-linked mutation of the BTK gene, which prevents maturation of B cells from pre-B cells to mature cells
• characterized by severe hypogammaglobulinemia, few mature B cells, and normal T-cell number and function
• presents with bacterial and enteroviral infections after 6 months of age
• diagnosed based on diminished levels of all immunoglobin isotypes, absent B cells, and present T cels
• treated with monthly IVIG replacement

Question 22

Chronic Granulomatous Disease

Answer 22

• X-linked recessive NADPH oxidase deficiency limits oxidative burst in neutrophils
• increased susceptibility to catalase positive organisms
• abnormal dihydrorhodamine test and no reaction to nitro blue tetrazolium dye
• treat with prophylactic TMP-SMX, itraconazole, and interferon-y
• bone marrow transplant is currative

Question 23

Which organisms are encapsulated?

Answer 23

Please SHINE my SKiS

• P. aeruginosa
• Streptococcus pneumoniae
• H. influenza type b
• N. meningitidis
• E. coli
• Salmonella spp.
• Klebsiella pneumoniae
• Group B Strep

Question 24

Which organisms are catalase positive?

Answer 24

Cats Need PLACESS to Belch their Hairballs

• Cat = catalase positive
• Nocardia
• Pseudomonas cepacia
• Listeria
• Aspergillus
• Candida
• E. Coli
• Staph
• Serratia
• B cepacia
• H pylori

Question 25

Schwachman-Diamond Syndrome

Answer 25

• an autosomal recessive condition
• characterized by decreased neutrophil chemotaxis, cyclic neutropenia, and pancreatic exocrine insufficiency
• often presents with recurrent soft tissue infections, chronic diarrhea, and failure to thrive

Question 26

Chediak-Higashi Syndrome

Answer 26

• autosomal recessive defect in the lysosomal trafficking regulator LYST which results in a microtubule defect that impairs fusion of phagosomes with lysosomes
• increases one’s risk for pyogenic infections by Staph and Strep
• presents with pancytopenia because the microtubule defect impairs mitosis and leads to intramedullary death
• giant granules in leukocytes because they can’t be distributed and accumulate at the golgi instead
• presents with defective primary hemostasis due to abnormal dense granules in platelets
• albinism because melanocytes can’t hand off pigment to keratinocytes
• peripheral neuropathy because axonal and dendritic transport are impaired

Question 27

How does an early complement deficiency differ from a late complement deficiency?

Answer 27

• early component deficiency is associated with autoimmune disease
• late component deficiency is associated with meningococcal and gonoccal infections

Question 28

C1 Esterase Inhibitor Deficiency

Answer 28

• an AD disorder known as hereditary angioedema resulting form loss of the complement regulator
• there is unregulated activation of kallikrein, leading to increased levels of bradykinin, as well as accumulation of anaphylatoxins, which results in swelling
• ACE inhibitors are contraindicated because they can lead to bradykinin accumulation