Genetics and Disease — MCQs

Genetics and Disease Indian Medical PG Practice Questions and MCQs

Question 251: Which of the following is a common genetic mutation leading to hypoxia-induced polycythemia in patients with chronic mountain sickness?

A. EGFR gene mutation
B. JAK2 V617F mutation
C. HIF1α gene mutation
D. VHL gene mutation (Correct Answer)

Explanation: ***VHL gene mutation*** - **Von Hippel-Lindau (VHL) gene mutations** are associated with **Chuvash polycythemia**, a form of **primary familial congenital polycythemia (PFCP)**, which mimics chronic mountain sickness at normoxia by causing overproduction of red blood cells due to impaired **HIF-1α degradation**. - The VHL protein is a component of the **ubiquitin ligase complex** that targets **HIF-1α** for degradation under normoxic conditions. Dysfunction of VHL leads to constitutive activation of HIF-1α, over-expression of **erythropoietin (EPO)**, and subsequent **polycythemia** even at normal oxygen levels. *EGFR gene mutation* - **EGFR mutations** are commonly found in non-small cell lung cancer and are associated with tumor growth and response to targeted therapies, but they are not directly involved in the pathogenesis of **polycythemia** or its response to hypoxia. - These mutations primarily affect **cell proliferation and survival** pathways in cancerous cells, rather than erythropoiesis. *JAK2 V617F mutation* - The **JAK2 V617F mutation** is a hallmark of **myeloproliferative neoplasms (MPNs)**, particularly **polycythemia vera (PV)**, leading to constitutive activation of the JAK-STAT pathway and uncontrolled erythropoiesis independent of erythropoietin. - While it causes **polycythemia**, this is typically considered a primary, acquired bone marrow disorder, not directly linked to the hypoxia-sensing pathway dysregulation seen in **chronic mountain sickness**. *HIF1α gene mutation* - While **HIF-1α** is central to the hypoxic response, direct activating mutations in the **HIF1α gene** itself are generally not the most common genetic cause of **hypoxia-induced polycythemia** in humans. - The dysregulation typically occurs upstream, often through mutations in the **VHL gene**, which controls HIF-1α stability.

Question 252: A 35-year-old woman presents with hepatomegaly and arthritis. Laboratory results show high serum ferritin and transferrin saturation. Which genetic defect is likely?

A. Wilson's disease
B. Hemochromatosis (Correct Answer)
C. α1-antitrypsin deficiency
D. Gaucher disease

Explanation: ***Hemochromatosis*** - **Hepatomegaly** and **arthritis** are classic clinical manifestations of hemochromatosis, caused by **excessive iron deposition** in various organs. - **High serum ferritin** (reflecting total body iron stores) and **high transferrin saturation** (indicating increased iron absorption) are key laboratory findings for diagnosing hemochromatosis, which is predominantly caused by genetic defects in the **HFE gene** [1]. *Wilson's disease* - Characterized by impaired copper metabolism, leading to **copper accumulation** in the liver, brain, and other organs [2]. - Laboratory findings typically include **low serum ceruloplasmin** and high urinary copper excretion, rather than high ferritin and transferrin saturation [2]. *α1-antitrypsin deficiency* - This genetic disorder primarily affects the lungs (leading to **emphysema**) and liver (causing **cirrhosis** or **hepatitis**) due to a deficiency of protective α1-antitrypsin. - It would not explain the high serum ferritin or transferrin saturation, nor is arthritis a common primary symptom. *Gaucher disease* - A lysosomal storage disorder resulting from a deficiency of the **glucocerebrosidase enzyme**, leading to accumulation of **glucocerebroside** in macrophages. - Clinically presents with **hepatosplenomegaly**, bone pain, and cytopenias, but not typically with high ferritin or transferrin saturation, nor inflammatory arthritis as a primary feature.

Question 253: A patient with hemochromatosis experiences joint pain and fatigue. Which genetic test would confirm the diagnosis?

A. BRCA1 gene test
B. Lynch syndrome genetic test
C. HFE gene mutation test (Correct Answer)
D. MLH1 gene test

Explanation: ***HFE gene mutation test*** - **Hemochromatosis** is an iron overload disorder, and the most common hereditary form is caused by mutations in the **HFE gene**. - A positive **HFE gene mutation test**, particularly for C282Y and H63D mutations, is diagnostic for hereditary hemochromatosis in patients with compatible clinical findings [1]. *BRCA1 gene test* - The **BRCA1 gene test** is used to identify mutations associated with an increased risk of developing **breast cancer** and **ovarian cancer**, not hemochromatosis [2]. - This gene is a **tumor suppressor gene** involved in DNA repair [2]. *Lynch syndrome genetic test* - **Lynch syndrome genetic testing** identifies mutations in mismatch repair genes (like MLH1, MSH2, MSH6, PMS2) that predispose individuals to various cancers, particularly **colorectal cancer** and **endometrial cancer**. - It is not related to iron metabolism or hemochromatosis. *MLH1 gene test* - The **MLH1 gene test** is a specific component of **Lynch syndrome genetic testing**, looking for mutations in the **MLH1 gene**, which is a DNA mismatch repair gene. - Mutations in MLH1 are linked to increased cancer risk, not the iron overload seen in hemochromatosis.

Question 254: A patient presents with blue sclera and a history of frequent fractures. Which genetic disorder should be suspected based on these findings?

A. Marfan syndrome
B. Ehlers-Danlos syndrome
C. Osteogenesis imperfecta (Correct Answer)
D. Rickets

Explanation: ***Osteogenesis imperfecta*** - **Blue sclera** is a classic sign due to the thinness of the sclera revealing the underlying choroidal veins, and **frequent fractures** are caused by defective collagen synthesis. - This disorder is a group of genetic conditions primarily affecting **type I collagen**, which is crucial for bone and connective tissue formation. *Marfan syndrome* - Characterized by tall stature, **arachnodactyly**, long limbs, and abnormalities of the **cardiovascular system** (e.g., aortic dissection) and eyes (e.g., lens dislocation). - While it affects connective tissue, it does not typically present with blue sclera or bone fragility as primary symptoms. *Ehlers-Danlos syndrome* - Features include **skin hyperextensibility**, **joint hypermobility**, and tissue fragility, often leading to easy bruising and poor wound healing [1]. - Unlike osteogenesis imperfecta, **blue sclera** and recurrent fractures are not hallmark features [1]. *Rickets* - A condition caused by **vitamin D deficiency** leading to impaired bone mineralization, resulting in bone softening and deformities. - It does not involve blue sclera and is typically seen in children, while osteogenesis imperfecta is a genetic disorder presenting from birth.

Question 255: Which genetic syndrome is associated with hundreds of colorectal polyps and almost certain progression to colorectal cancer if left untreated?

A. Lynch syndrome
B. Peutz-Jeghers syndrome
C. Juvenile polyposis syndrome
D. Familial adenomatous polyposis (Correct Answer)

Explanation: ***Familial adenomatous polyposis*** - Characterized by the presence of **hundreds to thousands of colorectal polyps** [1], which invariably progress to **colorectal cancer** if untreated [1]. - Caused by mutations in the **APC gene** [1] and requires regular surveillance and early intervention. *Peutz-Jeghers syndrome* - Presents with **hamartomatous polyps** [1] and associated mucocutaneous pigmentations, but the polyp burden is typically much less than in familial adenomatous polyposis. - Although there is a **cancer risk** [1], it does not have the same near-certain progression to colorectal cancer as familial adenomatous polyposis. *Juvenile polyposis syndrome* - Involves multiple **juvenile polyps** [1], mostly in childhood, but they have a lower risk of cancer compared to familial adenomatous polyposis. - The associated cancer risk is not as high [1], with polyp formation typically seen as **benign**. *Lynch syndrome* - A hereditary condition associated with **non-polyposis colorectal cancer** [2] and endometrial cancer, but does not lead to numerous polyps. - Caused by mutations in **mismatch repair genes** [2] and includes a different cancer risk profile than familial adenomatous polyposis.

Question 256: A 40-year-old woman with a family history of early-onset breast cancer undergoes genetic testing and is found to have a BRCA1 mutation. What is the most appropriate management option for her?

A. Annual mammography
B. Prophylactic mastectomy (Correct Answer)
C. Tamoxifen therapy
D. Ovarian cancer screening

Explanation: ***Prophylactic mastectomy*** - For a woman with a **BRCA1 mutation** and a family history of early-onset breast cancer, prophylactic mastectomy significantly **reduces the risk of developing breast cancer** by over 90%. - This aggressive preventive measure is considered appropriate due to the **high lifetime risk** of breast cancer associated with BRCA1 mutations [1]. *Annual mammography* - While important for surveillance, **mammography is a screening tool**, not a preventive measure, and may not be sufficient on its own for individuals with a high genetic risk like BRCA1 mutation carriers [1]. - BRCA1-associated cancers can be **aggressive and develop quickly**, making early detection challenging even with annual imaging, and mammography has limitations in dense breasts. *Tamoxifen therapy* - **Tamoxifen** is a **selective estrogen receptor modulator (SERM)** used for breast cancer prevention, but it's more effective for **estrogen receptor-positive (ER+) breast cancers**. - **BRCA1-associated breast cancers** are often **triple-negative (ER-/PR-/HER2-)** and therefore less likely to respond to tamoxifen's mechanism of action. *Ovarian cancer screening* - While BRCA1 mutations also increase the risk of ovarian cancer, and ovarian cancer screening is important, the question specifically asks for the most appropriate management *for her*, implying a focus on breast cancer given the context. - **Ovarian cancer screening**, typically involving transvaginal ultrasound and Ca-125, has **limited effectiveness** for early detection and is not a primary preventive measure for breast cancer.

Question 257: Which is the most reliable method for diagnosing genetic disorders?

A. Blood tests
B. Family history assessment
C. Genetic testing (Correct Answer)
D. Clinical evaluation

Explanation: ***Genetic testing*** - **Genetic testing** directly analyzes DNA, RNA, or chromosomes to identify specific genetic variants or abnormalities responsible for a disorder [1]. - This method is highly **specific and sensitive** for confirming a genetic diagnosis, particularly when specific mutations or chromosomal changes are suspected [1]. *Blood tests* - While blood tests can sometimes indirectly suggest a genetic disorder (e.g., elevated enzyme levels), they don't directly analyze the **genetic material**. [2] - They are often used for **screening or monitoring** but are not definitive for diagnosing the underlying genetic cause. *Family history assessment* - **Family history** is crucial for identifying patterns of inheritance and assessing risk but does not provide a definitive diagnosis [1]. - It guides decisions for further testing but cannot confirm the presence of a specific **genetic mutation**. [1] *Clinical evaluation* - A **clinical evaluation** involves assessing symptoms, physical signs, and medical history, which can suggest a genetic disorder. - While essential for initial assessment and guiding diagnostic pathways, it does not confirm the **underlying genetic cause** without further specific testing.

Question 258: A 25-year-old with Gaucher disease type 1 and a GBA mutation, exhibiting significant residual β-glucocerebrosidase activity, what is the best initial treatment?

A. BMT
B. SRT with eliglustat (Correct Answer)
C. Chaperone tx with miglustat
D. ERT with imiglucerase

Explanation: **SRT with eliglustat** - *Eliglustat* is a **substrate reduction therapy (SRT)** that inhibits glucosylceramide synthase, reducing the production of glucocerebroside. - It is particularly effective for patients with **Gaucher disease type 1 (GD1)** who have certain *GBA mutations* and **residual β-glucocerebrosidase activity**, as indicated in the patient scenario. *ERT with imiglucerase* - **Enzyme replacement therapy (ERT)** using *imiglucerase* replaces the deficient enzyme, β-glucocerebrosidase. - While effective for GD1, *SRT* is often preferred as a first-line oral treatment for patients with an eligible genotype and **residual enzyme activity**, avoiding intravenous infusions. *Chaperone tx with miglustat* - *Miglustat* is another *SRT*, but it is typically used for patients with **Gaucher disease type 1** who cannot receive *ERT* or as an adjunct. - It has a less favorable side effect profile, including *gastrointestinal disturbances* and *peripheral neuropathy*, compared to *eliglustat*. *BMT* - **Bone marrow transplantation (BMT)** is a curative, but highly invasive and risky, treatment option for Gaucher disease. - It is generally reserved for severe cases, especially those with **neuropathic forms (type 2 or 3)**, or in patients unresponsive to other therapies, given its significant *morbidity and mortality risks*.

Question 259: Which condition is characterized by excessive copper accumulation in the liver and brain?

A. Hemochromatosis
B. Wilson's disease (Correct Answer)
C. Menkes disease
D. Alzheimer's disease

Explanation: ***Wilson's disease*** - This is an **autosomal recessive disorder** characterized by the inability to excrete copper, leading to its accumulation in organs like the **liver, brain, eyes, and kidneys**. [1] - Clinical manifestations include **hepatitis**, cirrhosis, **neurological symptoms** (tremors, dysarthria), and **Kayser-Fleischer rings** in the cornea. [1] *Hemochromatosis* - This condition involves **excessive iron accumulation**, primarily in the liver, heart, and pancreas, not copper. [2] - It leads to symptoms such as **fatigue**, joint pain, **diabetes mellitus**, and **cardiac dysfunction**. *Menkes disease* - This is a rare, **X-linked recessive disorder** characterized by **copper deficiency** due to impaired copper absorption and transport, despite sufficient dietary intake. - It results in neurological degeneration, **distinctive kinky hair**, and connective tissue abnormalities. *Alzheimer's disease* - This is a neurodegenerative disorder characterized by the accumulation of **amyloid-beta plaques** and **neurofibrillary tangles** (tau protein) in the brain. - It primarily causes progressive **memory loss** and cognitive decline, and is not directly related to copper accumulation.

Question 260: A 40-year-old man presents with liver disease and neurological symptoms. His serum ceruloplasmin levels are low. Which condition is most likely?

A. Hemochromatosis
B. Wilson disease (Correct Answer)
C. Acute intermittent porphyria
D. Primary biliary cirrhosis

Explanation: ***Wilson disease*** - **Wilson disease** is characterized by impaired copper metabolism, leading to copper accumulation in the liver, brain, and other organs, causing **liver disease** and **neurological symptoms** [1]. - **Low serum ceruloplasmin** is a hallmark finding, as ceruloplasmin is the primary copper-carrying protein in the blood, and its synthesis is defective in Wilson disease [4]. *Hemochromatosis* - **Hemochromatosis** is an iron overload disorder, not copper, and would present with elevated **ferritin** and **transferrin saturation**, not low ceruloplasmin [2]. - While it can cause liver disease, it is not associated with the distinct neurological symptoms seen in Wilson disease, and ceruloplasmin levels would typically be normal [2]. *Acute intermittent porphyria* - **Acute intermittent porphyria** is a genetic disorder affecting heme synthesis, leading to neurological and psychiatric symptoms, and acute abdominal pain [3]. - It does not involve copper metabolism, and **liver disease** is not a primary feature, nor are ceruloplasmin levels affected. *Primary biliary cirrhosis* - **Primary biliary cirrhosis** (now often called primary biliary cholangitis) is an autoimmune disease causing destruction of bile ducts within the liver, leading to **cholestatic liver disease**. - While it can cause liver damage, it is typically associated with **antimitochondrial antibodies (AMA)** and does not primarily cause neurological symptoms or low ceruloplasmin levels.

Practice by Chapter

Principles of Medical Genetics

Practice Questions

Genetic Testing and Counseling

Practice Questions

Single Gene Disorders

Practice Questions

Chromosomal Disorders

Practice Questions

Mitochondrial Diseases

Practice Questions

Pharmacogenomics

Practice Questions

Cancer Genetics

Practice Questions

Genetics of Common Diseases

Practice Questions

Epigenetics and Disease

Practice Questions

Genetic Basis of Developmental Disorders

Practice Questions

Ethical Issues in Medical Genetics

Practice Questions

Gene Therapy and Precision Medicine

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free