Immunology - Diseases & Specific Findings

Question 1

SS-A (anti-Ro) / SS-B (anti-La)

Answer 1

Sjogren’s Syndrome

Question 2

Dermatomyositis - Clinical and Histological Findings

Answer 2

Malar / heliotrope rash
‘Shawl sign’
Gottron’s papules / ‘mechanic hands’

Histology shows perimysial CD4 inflammation

Question 3

Polymyositis - Histology

Answer 3

Histology shows endomysial CD8 inflammation

Question 4

Nitroblue tetrazolium (NBT) test

Answer 4

Negative in chronic granulomatous disease

Looks for production of superoxide anion which reduces the test indicator to produce blue color

Question 5

Catalase positive bacteria

Answer 5

Pseudomonas
Listeria
Aspergillus
Candida
E. Coli
S. aureus
Serratia

Question 6

Pathogens associated with Guillian-Barre Syndrome

Answer 6

Campylobacter jejuni

CMV

Question 7

Pathogens associated with Hyper-IgM syndrome

Answer 7

Pyogenic infections, especially:

Pneumocystis
Cryptosporidium
CMV

Question 8

Pemphigus Vulgaris - Antibody, IF, special sign

Answer 8

anti-demoglein

IF shows antibodies surrounding epithelial cells in a ‘reticular’ arrangement

Positive Nikolsky sign = separation of the epidermis with mechanical stroking

Question 9

Direct Coomb’s Test

Answer 9

Used to detect the presence of anti-RBC antibodies in a patient’s serum sample

RBCs from patient serum are incubated with anti-IgG antibodies; if RBCs agglutinate then RBCs were bound by antibody

Question 10

Indirect Coomb’s Test

Answer 10

Used to detect antibodies in patient serum, i.e. prior to blood transfusion

Patient’s serum is mixed with donor RBCs; if antibodies are present in the serum which bind donor RBCs then addition of anti-IgG to the solution causes agglutination

Question 11

Seronegative arthropathies - HLA association

Answer 11

HLA B27

Psoriatic Arthritis
Ankylosing Spondylitis
IBD-related arthritis
Reactive arthritis

Question 12

Celiac Disease - HLA Association

Answer 12

DQ2

DQ8

Question 13

Diabetes Mellitus Type 1 - HLA Associations

Answer 13

DR3

DR4

Question 14

Which cytokines are secreted by Th2s?

Answer 14

IL-4 - Enhances class switching to IgE and IgG

IL-5 - Enhances class switching to IgA; stimulates growth and differentiation of eosinophils

IL-10 - Inhibits differentiation of T cell progenitors into Th1

Question 15

Which cytokines are secreted by Th1s?

Answer 15

IL-2 - Provides 2nd signal for activation of CTLs

IFNy - Stimulates macrophages

Question 16

Rheumatoid Arthritis - HLA Association

Answer 16

HLA DR4

Question 17

SLE - HLA Association

Answer 17

HLA DR2

HLA DR3

Question 18

Edrophonium challenge test

Answer 18

Edrophonium is a short-acting AChEI used to diagnose Myasthenia Gravis; symptoms of myasthenia gravis improve with administration of edrophonium

Question 19

Anti-phospholipid antibody

Answer 19

AKA ‘Lupus anticoagulant’ - acquired anti-phospholipid antibody; bind to platelet phospholipids, making them accessible to clotting factors and leading to recurrent venous and arterial thrombosis

Inhibits the function of exogenous platelet phospholipids used in PTT assay causing false elevation (looks like a bleeding disorder)

Requires lifelong anti-coagulation therapy

Reacts with cardiolipin antigen used in syphylis serology, causing false positives for syphilis

Question 20

What antibodies are most specific for SLE?

Answer 20

anti-Smith

anti-double stranded DNA

Question 21

Which auto-antibody causes false positives in syphylis testing?

Answer 21

Anti-phospholipid antibody (Lupus)

Question 22

What antibodies are seen in Churg-Strauss Syndrome?

Answer 22

anti-MPO

p-ANCA

Question 23

ANCA-associated vasculitidies

Answer 23

Churg-Strauss Syndrome
Wegener’s Granuloamotosis
Microscopic polyangiitis

Question 24

Negatively Birefringent crystals

Answer 24

Crystals are yellow under parallel light, blue under perpendicular light

Characteristic of monosodium urate (MSU) crystals seen in Gout

Question 25

Gout

Answer 25

Inflammatory monoarthritis caused by precipitation of monosodium urate (MSU) crystals in joints, secondary to hyperuricemia (90% due to under-excretion of urate) Presents as asymmetric appearance of painful, red, swollen joint, classically the MTP of the big toe (Pedagra); 20% eventually develop Gouty Nephropathy due to MSU deposition in adrenal medulla, uric acid renal stones causing renal failure Findings: Needle-shaped, negatively birefringent crystals in joint fluid Acute treatment = NSAIDs / Colchicine, Glucocorticoids Chronic treatment = Xanthine Oxidase inhibitors (Allopurinol)

Question 26

Drug-Induced Lupus

Answer 26

Seen in men and women equally, associated with anti-nuclear antibody (ANA) and anti-histone; not associated with anti-DNA antibodies (anti-dsDNA, anti-Smith) ``` Caused by: Hydralazine Isoniazid Procainamide Phenytoin ```

Question 27

Lambert-Eaton myasthenic syndrome

Answer 27

Autoimmune production of antibodies directed against the pre-synaptic voltage-gated Ca2+ channel at the NMJ; often occurs as paraneoplastic syndrome of small cell lung cancer Presents as proximal muscle weakness, diplopia, decreased DTRs; muscle weakness improves with exercise due to accumulation of pre-synaptic Ca2+

Question 28

Kaposi Sarcoma

Answer 28

Neoplasm of vascular endothelial cells caused by HHV-8; seen in the setting of immunosuppression (AIDS, transplant) Presents as dark, flat or papular lesions on the skin; may also affect GI tract and lungs Treated with alpha interferon

Question 29

Chronic mucocutaneous candidiasis

Answer 29

T cell dysfunction resulting in deficient or absent T-cell proliferation response to Candida antigens Presents as recurrent oral / esophageal thrush, vulvovaginitis Treated with fluconazole / capsofungin (for oral/esophageal) and topical -azole (for vulvovaginitis)

Question 30

X-linked (Bruton's) hypogammaglobulinemia

Answer 30

X-linked defect in BTK tyrosine kinase causing failure of B cell maturation and immunoglobulin production Presents with recurrent pyogenic bacterial infections after 6 months (once maternal IgG is depleted) Labs: Normal CD19+ B cell count, decreased Ig of all classes, absent/scanty lymph nodes and tonsils

Question 31

Selective IgA deficiency

Answer 31

Most common primary immunodeficiency Majority asymptomatic but can see airway or GI infections, as well as anaphylaxis to IgA-containing blood products Labs: Low IgA with normal IgG, IgM

Question 32

Severe Combined Immunodeficiency (SCID)

Answer 32

Autosomal recessive defect in adenosine deaminase enzyme; accumulation of ATP and dATP imbalances nucleotide pool via feedback inhibition of ribonucleotide reducetase, preventing DNA synthesis and decreasing lymphocyte count Presents with failure to thrive, chronic diarrhea, thrush; repeated bacterial, viral, fungal, and parasitic infections Findings: Absent thymic shadow on CXR, absent germinal centers on lymph node biopsy, low IgG/IgM, low / absent T cells