Genetics and Disease Practice Questions

Q: Revised Ghent criteria are used for the diagnosis of?

Marfan syndrome. Marfan syndrome - The Revised Ghent criteria are specifically designed for the clinical diagnosis of Marfan syndrome, evaluating major and minor criteria related to ocular, cardiovascular, skeletal, and dural manifestations. - These criteria provide a scoring system to assess the likelihood of the syndrome based on specific physical findings and genetic testing. Ehlers-Danlos syndrome - Ehlers-Danlos syndrome is diagnosed using its own specific clinical criteria, often focusing on skin hyperextensibility, joint hypermobility, and tissue fragility [1]. - There are multiple types of Ehlers-Danlos syndrome, each with distinct diagnostic features, but none rely on the Revised Ghent criteria [1]. Osteogenesis imperfecta - Osteogenesis imperfecta is primarily characterized by bone fragility and recurrent fractures, often with associated features like blue sclerae and hearing loss. - Its diagnosis is typically based on clinical presentation and confirmed by genetic testing for mutations in COL1A1 or COL1A2 genes, not the Ghent criteria. Duchenne muscular dystrophy - Duchenne muscular dystrophy is a X-linked recessive neuromuscular disorder characterized by progressive muscle weakness. - Diagnosis relies on clinical features like Gowers' sign, elevated creatine kinase (CK) levels, muscle biopsy findings, and genetic testing for mutations in the dystrophin gene.

Q: All are seen in Klinefelter syndrome, except which of the following?

Normal male phenotype. ***Normal male phenotype*** - Klinefelter syndrome (47, XXY) is characterized by a distinct phenotype that deviates from a normal male, including features such as **tall stature**, **gynecomastia**, and **small testes** [1]. - A normal male phenotype would imply the absence of these characteristic features. *Cognitive impairment* - While not severe, **mild cognitive and learning difficulties**, especially in language skills, are common in individuals with Klinefelter syndrome [1]. - This can manifest as problems with **expressive language** and **reading**. *Azoospermia* - **Azoospermia**, or the complete absence of sperm in semen, is a very common finding in Klinefelter syndrome due to testicular dysfunction and hypogonadism [1]. - This leads to **infertility**, which is a primary concern for affected individuals. *Elevated FSH level* - The **elevated FSH (follicle-stimulating hormone) level** is a hallmark of primary testicular failure in Klinefelter syndrome [1], [2]. - The damaged seminiferous tubules in the testes fail to produce inhibin, leading to a lack of negative feedback on the pituitary, thus increasing FSH [2].

Q: A patient diagnosed with an isolated increase in LDL, with a family history of the same disease in his father and brother, is likely to have a diagnosis of

LDL receptor mutation. ***LDL receptor mutation*** - An **isolated increase in LDL** with a strong **family history** (father and brother affected) is highly suggestive of **familial hypercholesterolemia**, which is most commonly caused by mutations in the **LDL receptor gene** [1]. - **LDL receptor mutations** lead to a reduced clearance of LDL from the blood, resulting in elevated LDL levels from birth [1]. *Familial type III hyperlipoproteinemia* - This condition is characterized by elevated levels of both **cholesterol and triglycerides**, specifically involving **remnant lipoproteins** (IDL), not an isolated increase in LDL [2]. - It is often associated with **palmar xanthomas** and **tuberous xanthomas**, which are not mentioned in the patient's presentation. *Abetalipoproteinemia* - This is a rare genetic disorder characterized by the **absence of apolipoprotein B**, leading to very low or undetectable levels of **LDL, VLDL, and chylomicrons**. - Patients typically present with **fat malabsorption, neurologic deficits**, and **retinitis pigmentosa**, which is contrary to an isolated increase in LDL. *Familial lipoprotein lipase deficiency* - This condition primarily causes a marked elevation in **chylomicrons and triglycerides** due to impaired clearance of triglyceride-rich lipoproteins. - It does not present as an isolated increase in LDL and is often associated with **eruptive xanthomas**, **pancreatitis**, and **hepatosplenomegaly**.

Q: What is the name of the treatment for type I tyrosinemia?

Nitisinone. ***Nitisinone*** - **Nitisinone** (NTBC) is the primary treatment for **tyrosinemia type I**, an inherited metabolic disorder. - It works by inhibiting **4-hydroxyphenylpyruvate dioxygenase**, an enzyme upstream in the tyrosine degradation pathway, preventing the formation of toxic metabolites. *No treatment* - Leaving **tyrosinemia type I** untreated leads to severe complications such as **liver failure**, **renal tubular dysfunction**, and **neurological crises**. - Without intervention, the disease is often **fatal** in infancy or early childhood. *Symptomatic treatment only* - While supportive care is important, **symptomatic treatment alone** is insufficient to prevent the progressive and severe organ damage associated with tyrosinemia type I. - The underlying metabolic defect producing toxic metabolites must be addressed directly to achieve positive outcomes. *Vitamin B complex* - **Vitamin B complex** is not an effective treatment for type I tyrosinemia. - While certain inborn errors of metabolism respond to specific vitamin cofactors, **tyrosinemia type I** requires specific inhibition of a metabolic pathway, which vitamins cannot provide.

Q: Which of the following statements about alpha-1 antitrypsin deficiency is true?

May cause cholestatic jaundice. ***All of the above*** - All listed statements accurately describe aspects of **alpha-1 antitrypsin deficiency** [1], including its nature, genetic inheritance, and potential consequences. - This condition allows **proteolytic enzymes** to damage the lungs and liver [1], among other organs, confirming all options as true. *Deficiency of protease inhibitor* - While alpha-1 antitrypsin is a **protease inhibitor** [1], the wording can be confusing as it implies a more general condition rather than specifying the genetic aspect of **alpha-1 antitrypsin deficiency**. - This oes not encompass the full clinical implications of the deficiency, making it insufficient alone to describe the condition. *Autosomal recessive* - The inheritance pattern of alpha-1 antitrypsin deficiency is actually **autosomal co-dominant**, not strictly recessive. - This means that individuals can express both normal and abnormal alleles, which this option fails to capture accurately. *May cause cholestatic jaundice* - Though **cholestatic jaundice** can occur due to liver involvement in severe cases, it is not a defining feature of the deficiency and may be considered as a rare complication. - More commonly, the condition leads to **emphysema** [1][2] and liver cirrhosis, highlighting the insufficiency of this statement on its own.

Q: Which of the following is a single gene autosomal recessive disease?

Wilson's disease. ***Wilson's disease*** - This is an **autosomal recessive disorder** [1] characterized by excessive **copper accumulation** in the liver, brain, and other organs due to a mutation in the ATP7B gene. - Manifestations include **hepatic dysfunction**, neurological symptoms, and characteristic **Kayser-Fleischer rings** in the eyes [1]. *Tuberous sclerosis* - This is an **autosomal dominant disorder** caused by mutations in the TSC1 or TSC2 genes, leading to the formation of benign tumors in multiple organs. - Clinical features include **epilepsy**, intellectual disability, facial angiofibromas, and renal angiomyolipomas. *Huntington's disease* - This is an **autosomal dominant neurodegenerative disorder** caused by a CAG trinucleotide repeat expansion in the HTT gene. - It presents with **progressive chorea**, psychiatric symptoms, and cognitive decline, typically in mid-adulthood. *Schizophrenia* - This is a **complex psychiatric disorder** with a multifactorial etiology, involving a combination of genetic predisposition and environmental factors. - It is not a single gene disorder but rather involves many genes contributing to risk, indicating a **polygenic inheritance pattern**.

Q: Mutation in the NPHS1 gene causes which of the following disease?

Congenital Finnish type nephrotic syndrome. ***Congenital Finnish type nephrotic syndrome*** - This syndrome is caused by mutations in the **NPHS1 gene**, encoding **nephrin**, a key component of the **slit diaphragm** in glomerular podocytes. - The dysfunctional nephrin leads to severe **proteinuria** and nephrotic syndrome from birth. *Alport syndrome* - This syndrome is caused by mutations in genes encoding **Type IV collagen**, primarily **COL4A5 (X-linked)**, which is crucial for basement membrane integrity [3]. - Characterized by **hematuria**, progressive renal failure, **sensorineural hearing loss**, and ocular abnormalities. *Focal segmental glomerulonephritis* - While some forms can be genetic, **NPHS1 mutations** are not typically the primary cause of genetic [1]. - This condition involves scarring of specific parts of some glomeruli and has various primary and secondary causes [2]. *Nail patella syndrome* - This syndrome is caused by mutations in the **LMX1B gene**, which plays a role in early limb and kidney development. - It is characterized by **nail dysplasia**, absent or hypoplastic patellae, elbow abnormalities, and iliac horns, sometimes with renal involvement.

Q: Which one of the following is an autosomal dominant disorder?

Hereditary spherocytosis. ***Hereditary spherocytosis*** - It is characterized by **autosomal dominant inheritance** [1], leading to the destruction of red blood cells. - Mutations in proteins that maintain the **red blood cell membrane** integrity result in spherocyte formation [1]. *Cystic fibrosis* - This condition follows a **autosomal recessive inheritance pattern**, requiring two copies of the mutated gene for disease manifestation. - It is caused by mutations in the **CFTR gene**, affecting chloride transport and leading to thick secretions. *G-6PD deficiency* - This disorder is inherited in an **X-linked recessive manner** [2], primarily affecting males and transmitted through carrier females. - Characterized by **hemolytic anemia** triggered by certain medications or infections, it does not follow dominant inheritance [2]. *Sickle cell anemia* - Sickle cell anemia is also an **autosomal recessive disorder** [3], meaning affected individuals must inherit two copies of the sickle cell gene. - It results in a mutation in the **HBB gene**, leading to the production of abnormal hemoglobin (HbS) [3].

Q: What specific hand abnormalities are associated with Marfan syndrome?

Arachnodactyly. ***Arachnodactyly*** - This term refers to **long, slender fingers and toes**, resembling a spider's appendages, which is a classic musculoskeletal manifestation of **Marfan syndrome**. - It results from the generalized connective tissue disorder affecting the deposition of **fibrillin-1**, leading to excessive bone growth. *Syndactyly* - This condition involves the **fusion of adjacent digits**, either soft tissue or bone, rather than unusually long fingers. - It is typically a congenital anomaly not specifically associated with Marfan syndrome. *Clinodactyly* - This describes the **curving or deviation of a digit**, usually the fifth finger, due to an abnormally shaped bone [1]. - While a digital anomaly, it is not a hallmark feature of Marfan syndrome, which is characterized by digit length. *Brachydactyly* - This condition is characterized by **unusually short fingers and toes**, which is the opposite of the digital characteristic seen in Marfan syndrome. - It can be a feature of various genetic disorders but not Marfan syndrome.

Q: Which of the following laboratory findings is the MOST characteristic of Wilson's disease?

Increased urinary copper excretion. ***Low ceruloplasmin and high urinary copper*** - In Wilson's disease, there is decreased **ceruloplasmin** due to impaired copper metabolism, leading to low levels in the serum [1]. - The condition results in **increased urinary copper excretion**, which is a hallmark feature and confirms the diagnosis [2]. *Low urinary copper* - Wilson's disease presents with **high urinary copper** levels due to excessive copper being expelled by the kidneys. - **Low urinary copper** would suggest a different condition, such as **Chronic liver disease** or **renal tubular disorders**. *High ceruloplasmin* - Patients with Wilson's disease have **low ceruloplasmin levels** rather than high, indicating ineffective copper transport [1]. - **High ceruloplasmin** levels are typically associated with conditions like **inflammation** or **pregnancy** rather than Wilson's disease. *Low serum copper* - In Wilson's disease, serum copper levels are typically **normal or elevated**, not low. - The primary defect is in the transport of copper, resulting in accumulation in tissues, not a deficiency in serum levels [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Liver and Gallbladder, pp. 855-856. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 132-133.

Question 1

Revised Ghent criteria are used for the diagnosis of?

Accepted Answer

Marfan syndrome

Answer

Osteogenesis imperfecta

Answer

Duchenne muscular dystrophy

Answer

Ehlers-Danlos syndrome

Question 2

All are seen in Klinefelter syndrome, except which of the following?

Accepted Answer

Normal male phenotype

Answer

Azoospermia

Answer

Cognitive impairment

Answer

Elevated FSH level

Question 3

A patient diagnosed with an isolated increase in LDL, with a family history of the same disease in his father and brother, is likely to have a diagnosis of

Accepted Answer

LDL receptor mutation

Answer

Abetalipoproteinemia

Answer

Familial type III hyperlipoproteinemia

Answer

Familial lipoprotein lipase deficiency

Question 4

What is the name of the treatment for type I tyrosinemia?

Accepted Answer

Nitisinone

Answer

No treatment

Answer

Vitamin B complex

Answer

Symptomatic treatment only

Question 5

Which of the following statements about alpha-1 antitrypsin deficiency is true?

Accepted Answer

May cause cholestatic jaundice

Question 6

Which of the following is a single gene autosomal recessive disease?

Accepted Answer

Wilson's disease

Answer

Tuberous sclerosis

Answer

Huntington's disease

Answer

Schizophrenia

Question 7

Mutation in the NPHS1 gene causes which of the following disease?

Accepted Answer

Congenital Finnish type nephrotic syndrome

Answer

Alport syndrome

Answer

Focal segmental glomerulonephritis

Answer

nail patella syndrome

Question 8

Which one of the following is an autosomal dominant disorder?

Accepted Answer

Hereditary spherocytosis

Answer

Cystic fibrosis

Answer

Sickle cell anemia

Answer

G-6PD deficiency

Question 9

What specific hand abnormalities are associated with Marfan syndrome?

Accepted Answer

Arachnodactyly

Answer

Brachydactyly

Answer

Clinodactyly

Answer

Syndactyly

Question 10

Which of the following laboratory findings is the MOST characteristic of Wilson's disease?

Accepted Answer

Increased urinary copper excretion

Answer

Elevated serum copper

Answer

Low serum copper

Answer

Low ceruloplasmin

Genetics and Disease — MCQs

Genetics and Disease — MCQs

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