Autoimmune Diseases Practice Questions
20 free Autoimmune Diseases practice questions for the Microbiology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Which of the following is the most sensitive screening test for Systemic Lupus Erythematosus (SLE)?
- A Anti-dsDNA antibodies
- B Anti-Smith (Sm) antibodies
- C Antinuclear antibodies (ANA)
- D Antiphospholipid antibodies (aPL)
Correct answer: Antinuclear antibodies (ANA)
ANA is positive in virtually all patients with SLE (95–99% sensitivity), making it the best screening tool. However, it lacks specificity as it can be positive in other autoimmune diseases and even healthy individuals.
The 'rim' or peripheral pattern of immunofluorescence for Antinuclear Antibodies (ANA) is most highly associated with antibodies against:
- A Centromere-associated proteins
- B Double-stranded DNA (dsDNA)
- C Core histone proteins
- D RNA polymerase III
Correct answer: Double-stranded DNA (dsDNA)
Anti-dsDNA antibodies typically produce a peripheral or rim-like staining pattern of the nucleus. This finding is highly specific for Systemic Lupus Erythematosus.
Which specific antibody is considered most diagnostic for Drug-Induced Lupus Erythematosus?
- A Anti-Sm
- B Anti-Ro (SSA)
- C Anti-histone
- D Anti-Jo-1
Correct answer: Anti-histone
Anti-histone antibodies are present in over 95% of drug-induced lupus cases (triggered by drugs like hydralazine or procainamide). Unlike idiopathic SLE, anti-dsDNA antibodies are usually absent in this variant.
What is the primary pathological mechanism in Myasthenia Gravis?
- A Destruction of the myelin sheath in the CNS
- B Antibody-mediated blockade of synaptic ACh receptors
- C T-cell mediated destruction of peripheral nerve axons
- D Fibrinoid necrosis of the neuromuscular junction
Correct answer: Antibody-mediated blockade of synaptic ACh receptors
Myasthenia Gravis is a Type II hypersensitivity disorder where autoantibodies bind to post-synaptic acetylcholine receptors. This leads to receptor internalization and impaired neuromuscular transmission, causing muscle weakness.
In Sjogren syndrome, the immune-mediated destruction primarily targets which of the following tissues?
- A Synovial membranes of joints
- B Lacrimal and salivary glands
- C Islets of Langerhans in the pancreas
- D Adrenal cortex and medulla
Correct answer: Lacrimal and salivary glands
Sjogren syndrome is a chronic disease characterized by lymphocytic infiltration (mainly CD4+ T-cells) of exocrine glands. This leads to the classic symptoms of dry eyes (keratoconjunctivitis sicca) and dry mouth (xerostomia).
Which histological feature is characteristic of the 'Libman-Sacks' endocarditis seen in SLE?
- A Large, irregular friable vegetations along the free valve edges
- B Small sterile vegetations on both valve leaflet surfaces
- C Perforation of the mitral valve cusp
- D Calcific stenosis of the aortic valve
Correct answer: Small sterile vegetations on both valve leaflet surfaces
Libman-Sacks endocarditis involves small, verrucous, non-bacterial vegetations. They are unique because they can develop on the undersurfaces of the valves, the chordae tendineae, or the endocardial surfaces.
Systemic Sclerosis (Scleroderma) is characterized by excessive fibrosis. Which cytokine is considered a major mediator of this fibrotic response?
- A IL-1
- B TGF-β
- C TNF-α
- D IFN-γ
Correct answer: TGF-β
TGF-beta is a potent profibrotic cytokine that stimulates the synthesis of collagen and other extracellular matrix proteins by fibroblasts. Its overproduction is central to the skin and visceral thickening seen in scleroderma.
Which of the following is a component of the CREST syndrome variant of Limited Scleroderma?
- A Erythema marginatum
- B Hepatosplenomegaly
- C Esophageal dysmotility
- D Diffuse glomerulonephritis
Correct answer: Esophageal dysmotility
CREST stands for Calcinosis, Raynaud phenomenon, Esophageal dysmotility, Sclerodactyly, and Telangiectasia. Esophageal dysfunction results from submucosal fibrosis and atrophy of the muscularis propria.
Patients with which of the following HLA alleles have a significantly higher risk of developing Ankylosing Spondylitis?
- A HLA-DR3
- B HLA-DR4
- C HLA-B27
- D HLA-DQ8
Correct answer: HLA-B27
The association between HLA-B27 and Ankylosing Spondylitis is one of the strongest known HLA-disease links. Approximately 90% of affected individuals carry this allele compared to less than 10% of the general population.
What is the characteristic histological finding in the joints of a patient with Rheumatoid Arthritis?
- A Thinning of the synovium and loss of lubrication
- B Pannus formation with chronic synovial hyperplasia
- C Urate crystal deposition with giant cell reaction
- D Extensive subchondral bone cysts without inflammation
Correct answer: Pannus formation with chronic synovial hyperplasia
Rheumatoid Arthritis involves a chronic proliferative synovitis. A 'pannus' is a mass of edematous synovium, inflammatory cells, granulation tissue, and fibroblasts that erodes the underlying articular cartilage.
Which antibody is most specific for the diagnosis of Rheumatoid Arthritis?
- A Antinuclear antibody (ANA, low titer)
- B Rheumatoid Factor (RF, IgM class)
- C Anti-CCP (anti-citrullinated protein)
- D Anti-smooth muscle antibody (ASMA)
Correct answer: Anti-CCP (anti-citrullinated protein)
While Rheumatoid Factor is common, Anti-CCP antibodies have a specificity of about 95% for Rheumatoid Arthritis. They are often detectable in the blood long before clinical symptoms appear.
In Hashimoto thyroiditis, what is the primary cause of follicular cell destruction?
- A CD8+ T-cell killing and ADCC via anti-thyroid antibodies
- B Excessive stimulation by TSH-receptor antibodies
- C Granulomatous inflammation due to chronic fungal infection
- D Ischemic necrosis from fibrinoid vasculitis
Correct answer: CD8+ T-cell killing and ADCC via anti-thyroid antibodies
Hashimoto thyroiditis involves a breakdown in self-tolerance to thyroid autoantigens. Destruction is mediated by cytotoxic T-cells, cytokines from Th1 cells, and the binding of antithyroid antibodies followed by ADCC.
Which of the following is a hallmark of 'Mixed Connective Tissue Disease' (MCTD)?
- A High titers of anti-U1 RNP antibodies
- B Absence of ANA on screening
- C Permanent absence of Raynaud phenomenon
- D Resistance to corticosteroid therapy
Correct answer: High titers of anti-U1 RNP antibodies
MCTD is a clinical 'overlap' syndrome with features of SLE, systemic sclerosis, and polymyositis. A high titer of anti-U1 RNP is the defining serological characteristic.
Which autoimmune disease is associated with 'heliotrope rash' and 'Gottron papules'?
- A Lupus (SLE)
- B Dermatomyositis
- C Polyarteritis
- D Psoriatic arthritis
Correct answer: Dermatomyositis
Dermatomyositis is an inflammatory myopathy with distinct cutaneous involvement. The heliotrope rash (lilac discoloration of the eyelids) and Gottron papules (scaling lesions over the knuckles) are diagnostic skin findings.
Anti-Jo-1 antibodies are most commonly found in patients with which condition?
- A Primary Sjogren syndrome
- B Polymyositis / Dermatomyositis
- C Primary biliary cholangitis
- D Antiphospholipid antibody syndrome
Correct answer: Polymyositis / Dermatomyositis
Anti-Jo-1 is an antibody against histidyl-tRNA synthetase. It is present in about 25% of patients with polymyositis or dermatomyositis, especially those with interstitial lung disease and 'mechanic's hands'.
What is the primary immunological defect in the development of Type 1 Diabetes Mellitus?
- A Autoantibody lysis of acinar cells
- B T-cell mediated pancreatic beta cell destruction
- C Immune complex deposition in pancreatic ducts
- D Overproduction of insulin-neutralizing autoantibodies
Correct answer: T-cell mediated pancreatic beta cell destruction
Type 1 Diabetes is a T-cell mediated autoimmune disease. Islet-infiltrating lymphocytes (insulitis), specifically CD8+ cytotoxic T-cells, destroy the insulin-producing beta cells in the islets of Langerhans.
Antiphospholipid Syndrome (APS) can occur in SLE patients and is characterized by which clinical triad?
- A Fever, joint pain, and unexplained weight loss
- B Thrombosis, pregnancy loss, and thrombocytopenia
- C Dry eyes, xerostomia, and bilateral parotid swelling
- D Hematuria, hemoptysis, and severe hypertension
Correct answer: Thrombosis, pregnancy loss, and thrombocytopenia
APS is a hypercoagulable state. The antibodies interfere with phospholipids in the coagulation cascade, paradoxically prolonging the PTT in vitro while causing clotting and pregnancy complications in vivo.
Which HLA alleles are most strongly associated with Systemic Lupus Erythematosus?
- A HLA-B27 and HLA-B8
- B HLA-DR2 and HLA-DR3
- C HLA-DR4 and HLA-DQ8
- D HLA-A3 and HLA-B7
Correct answer: HLA-DR2 and HLA-DR3
HLA-DR2 and HLA-DR3 are the MHC class II alleles most frequently linked to an increased susceptibility to SLE in Caucasian populations.
The presence of 'Aschoff bodies' is specific to which autoimmune-related condition?
- A Rheumatoid nodules
- B Acute Rheumatic Fever
- C Systemic Sclerosis
- D Goodpasture syndrome
Correct answer: Acute Rheumatic Fever
Aschoff bodies are pathognomonic myocardial lesions in acute rheumatic fever. They are areas of focal fibrinoid necrosis surrounded by lymphocytes, plasma cells, and large activated macrophages called Anitschkow cells.
Which mechanism of central tolerance involves the deletion of self-reactive T-cells in the thymus?
- A Anergy
- B Negative selection
- C Suppression by T-regulatory cells
- D Antigen sequestration
Correct answer: Negative selection
Central tolerance occurs during lymphocyte development. In the thymus, immature T-cells that recognize self-antigens with high affinity undergo apoptosis, a process known as negative selection.