Genetics and Disease Practice Questions

Q: A 25-year-old man presents for a routine examination and is found to have an early diastolic murmur on examination. Clinical findings suggest hypertrophic cardiomyopathy. The family pedigree shows affected individuals in three consecutive generations with both males and females affected, and no generation is skipped. What is the most likely mode of inheritance of this genetic condition?

AD. ***AD (Autosomal Dominant)*** - The presence of affected individuals in **three consecutive generations** without skipping generations is a hallmark of autosomal dominant inheritance [1]. - Both **males and females are affected** equally, indicating it is not X-linked [1]. *AR (Autosomal Recessive)* - **Autosomal recessive** conditions typically **skip generations** and affect siblings, as carriers can pass on the gene without expressing the disease. - Such conditions often show a **25% recurrence risk** in offspring of two carrier parents, which is not suggested here. *XLD (X-linked Dominant)* - **X-linked dominant** inheritance would show **affected fathers passing the trait to all their daughters** but none of their sons, which is not specified. - Affected mothers would have a **50% chance** of passing the trait to each child, regardless of sex. *XLR (X-linked Recessive)* - **X-linked recessive** conditions predominantly affect **males**, and affected fathers cannot pass the trait to their sons. - Females are typically carriers, and affected males often have unaffected parents, which would imply skipping generations.

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: 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: Which of the following conditions is characterized by the presence of telangiectasia?

Hereditary hemorrhagic telangiectasia. ***Hereditary hemorrhagic telangiectasia*** - This condition, also known as **Osler-Weber-Rendu disease**, is a **genetic disorder** resulting in abnormal blood vessel formation, leading to **telangiectasias** and arteriovenous malformations that can cause significant bleeding. - Key diagnostic criteria include spontaneous recurrent nosebleeds, multiple mucocutaneous telangiectasias, visceral organ involvement (e.g., pulmonary, hepatic, cerebral AVMs), and a family history. *Telangiectasia due to systemic sclerosis* - While telangiectasias can be a feature of **systemic sclerosis** (especially the limited cutaneous form, **CREST syndrome**), they are typically localized and are not the primary defining characteristic of the disease. - Systemic sclerosis is primarily characterized by **fibrosis of skin and internal organs**, and the telangiectasias are a secondary manifestation, not the fundamental underpinning of the condition as in HHT. *Telangiectasia due to rosacea* - **Rosacea** is a chronic inflammatory skin condition characterized by facial erythema, papules, pustules, and **telangiectasias**, particularly on the cheeks and nose. - However, rosacea-associated telangiectasias are localized to the face and are part of a broader inflammatory dermatological process, distinct from the systemic vascular abnormalities seen in HHT. *Acquired telangiectasia due to sun exposure* - **Sun exposure** can indeed cause **telangiectasias**, particularly on sun-damaged skin, due to chronic photodamage to dermal blood vessels. - These are generally localized, non-syndromic, and a result of environmental factors rather than a systemic or inherited disorder as seen in hereditary hemorrhagic telangiectasia.

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 mode of inheritance for the most common mutation in Alport syndrome, which is found in the COL4A5 gene?

X-linked inheritance, primarily affecting males. ***X-linked*** - The most common mutation in **Alport syndrome** occurs in the **COL4A5** gene, which is primarily associated with X-linked inheritance. - Males are more severely affected due to their single X chromosome, while females may present with milder symptoms. *Autosomal recessive* - Alport syndrome is not primarily transmitted through **autosomal recessive inheritance**, though there are rare forms that can be. - The typical inheritance pattern linked to **COL4A5 mutations** is X-linked rather than autosomal. *Variable, autosomal dominant or autosomal recessive* - This option suggests a **variable mode of inheritance**, which is misleading as the most common form related to COL4A5 is specifically X-linked. - Alport syndrome does exhibit some forms of **autosomal dominant transmission**, but it is not the most common. *Autosomal dominant* - While some forms of Alport syndrome can be autosomal dominant, the **predominant mutations** are X-linked, particularly in the COL4A5 gene. - Patients with autosomal dominant forms usually have a less severe disease course compared to those with X-linked forms.

Q: Which of the following conditions is least likely to be inherited in a familial manner?

Factor V Leiden mutation. ***Thalassemia*** - Thalassemia is a **genetic blood disorder** caused by mutations in hemoglobin genes [1], but biomarkers for diagnosis can sometimes arise **de novo**. - It exhibits **incomplete penetrance** and variable expressivity, meaning not all family members may express the trait despite sharing genes. *Hemophilia* - Hemophilia is a **X-linked recessive** disorder predominantly affecting males, passed from carrier mothers to sons [2]. - The condition leads to **deficiencies in blood clotting factors**, which are inherited in a recognizable familial pattern, though about 30% of patients have no family history due to new mutations [2]. *Factor V Leiden mutation* - Factor V Leiden is an **autosomal dominant** genetic mutation leading to increased clotting risk, often inherited from affected parents. - It presents as a familial tendency towards **venous thromboembolism**, clearly identifying its transmission. *Sickle cell anemia* - Sickle cell anemia is an **autosomal recessive** disorder, requiring two copies of the mutated gene for expression, commonly inherited within families [1]. - It leads to characteristic **sickle-shaped red blood cells**, with a clear familial pattern of inheritance [1]. It is important to distinguish that **hereditary disorders** are by definition transmitted through generations and are therefore **familial**.

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 is a characteristic feature of Werner's syndrome?

Accelerated aging. ***Premature ageing*** - Werner's disease is characterized by **accelerated aging** and the appearance of age-related diseases at a much younger age [1]. - Patients often present with **sclerosis**, hair graying, and other features associated with advanced age [1]. *Multiple cancer* - While patients with Werner's may have **increased cancer risk**, it is not a direct hallmark of the disease. - The primary feature focuses on **premature aging** rather than a significant predisposition to multiple cancers [1]. *Intestinal polyps* - Intestinal polyps are not typically associated with Werner's disease but are more characteristic of conditions like **Familial adenomatous polyposis (FAP)**. - The main pathology of Werner's lies in the **genetic mechanisms** behind aging, not specifically in gastrointestinal manifestations [1]. *Lax joints* - Although some connective tissue disorders can present with lax joints, this is not a feature of Werner's disease. - Werner's disease primarily involves **age-related changes** rather than joint laxity or hypermobility [1].

Q: Which inheritance pattern is associated with adult polycystic kidney disease?

Autosomal dominant. ***Autosomal dominant*** - Adult polycystic kidney disease (**APKD**) is primarily inherited in an **autosomal dominant** manner, meaning a single copy of the mutated gene can cause the disease [1]. - It is commonly associated with **bilateral renal cysts** and can lead to chronic kidney disease owing to the progressive nature of the cysts [1]. *X-linked dominant* - X-linked conditions predominantly affect **males**, and the characteristics of APKD do not align with X-linked inheritance patterns. - There are no known mechanisms or mutations related to APKD that operate through an **X-linked dominant** inheritance. *Autosomal recessive* - Autosomal recessive conditions require two copies of the mutated gene for expression, which is not the case in APKD. - This option is more characteristic of **infantile polycystic kidney disease**, which is rare and different from APKD. *X-linked recessive* - Similar to , X-linked recessive traits primarily affect **males**, which contradicts the established inheritance pattern of APKD. - The condition does not show linkage to **X chromosome** mutations, making this option incorrect.

Question 1

A 25-year-old man presents for a routine examination and is found to have an early diastolic murmur on examination. Clinical findings suggest hypertrophic cardiomyopathy. The family pedigree shows affected individuals in three consecutive generations with both males and females affected, and no generation is skipped. What is the most likely mode of inheritance of this genetic condition?

Accepted Answer

AD

Answer

AR

Answer

XLD

Answer

XLR

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

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 4

Which of the following conditions is characterized by the presence of telangiectasia?

Accepted Answer

Hereditary hemorrhagic telangiectasia

Answer

Telangiectasia due to systemic sclerosis

Answer

Telangiectasia due to rosacea

Answer

Acquired telangiectasia due to sun exposure

Question 5

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 6

What is the mode of inheritance for the most common mutation in Alport syndrome, which is found in the COL4A5 gene?

Accepted Answer

X-linked inheritance, primarily affecting males

Answer

Variable inheritance patterns

Answer

Autosomal dominant inheritance

Answer

Autosomal recessive inheritance

Question 7

Which of the following conditions is least likely to be inherited in a familial manner?

Accepted Answer

Factor V Leiden mutation

Answer

Hemophilia

Answer

Sickle cell anemia

Answer

Acquired thrombotic thrombocytopenic purpura (TTP)

Question 8

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 9

Which of the following is a characteristic feature of Werner's syndrome?

Accepted Answer

Accelerated aging

Answer

Joint laxity

Answer

Multiple cancers

Answer

Intestinal polyps

Question 10

Which inheritance pattern is associated with adult polycystic kidney disease?

Accepted Answer

Autosomal dominant

Answer

Autosomal recessive

Answer

X-linked recessive

Answer

X-linked dominant

Genetics and Disease — MCQs

Genetics and Disease — MCQs

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