Genetic Eye Diseases in Children — MCQs
When should surgery be performed for congenital cataracts with visual disturbances?
Pattern of inheritance where mother transmits disease to all children -
Which of the following is a specific sign of albinism?
Which disease will show the mode of inheritance depicted in this pedigree?
A patient presents with headache, confusion, and a diagnosis of a brain tumor. The family history reveals brain and kidney tumors. What is the most likely diagnosis?
What is the cause of glaucoma in retinoblastoma?
What is the most common type of congenital cataract?
A 30-year-old female presents with night blindness and peripheral vision loss. Likely diagnosis?
Cataracts and PDA in a newborn suggests in utero infection with which viral family?
A 10-year-old child presents with inward turning of the right eye, and examination shows limited abduction of the affected eye. What is the most likely diagnosis?
Genetic Eye Diseases in Children Indian Medical PG Practice Questions and MCQs
Question 1: When should surgery be performed for congenital cataracts with visual disturbances?
- A. After 2 months
- B. After 4 months
- C. After 1 year
- D. As soon as possible (within 6-10 weeks) (Correct Answer)
Explanation: ***As soon as possible (within 6-10 weeks)*** - **Early surgical intervention** (within the first few weeks of life) is crucial for congenital cataracts to prevent **irreversible visual deficits**, such as **amblyopia**. - The brain's visual pathways develop rapidly in infancy, and prolonged visual deprivation from cataracts can lead to **permanent impairment**. *After 2 months* - This time frame represents a delay that can increase the risk of **amblyopia** and poorer visual outcomes. - The critical period for visual development is very early in life, making immediate intervention vital. *After 4 months* - A delay of four months significantly increases the likelihood of **dense amblyopia** and **strabismus**, making complete visual rehabilitation much more challenging. - At this age, the potential for achieving good vision post-surgery dramatically decreases due to entrenched abnormal visual processing. *After 1 year* - Performing surgery at one year or later for congenital cataracts is generally considered too late, often resulting in **profound and irreversible amblyopia**. - The visual system will have already established abnormal connections, making significant improvement in visual acuity unlikely.
Question 2: Pattern of inheritance where mother transmits disease to all children -
- A. Mitochondrial inheritance (Correct Answer)
- B. X-linked recessive
- C. Autosomal dominant
- D. Autosomal recessive
Explanation: ***Mitochondrial inheritance*** - Mitochondrial DNA (mtDNA) is exclusively inherited from the **mother**, meaning all children of an affected mother will inherit the mitochondrial disease. - Fathers do not pass on their mtDNA to their offspring, so an affected father's children will not inherit mitochondrial conditions from him. *X-linked recessive* - In X-linked recessive inheritance, sons have a 50% chance of being affected if their mother is a carrier, and daughters have a 50% chance of being carriers. - It does not guarantee that **all children** will inherit the disease from an affected mother; affected mothers would pass the X-linked gene to all sons (who would be affected) and all daughters (who would be carriers or affected depending on the other X chromosome). *Autosomal dominant* - In autosomal dominant inheritance, an affected parent has a 50% chance of passing the allele to **each child**, regardless of sex. - This pattern means not all children will necessarily inherit the disease, and both sexes are affected equally. *Autosomal recessive* - For autosomal recessive diseases, both parents must be carriers or affected for a child to inherit the disease, and even then, there is only a 25% chance for each child to be affected if both parents are carriers. - This pattern does not result in **all children** inheriting the disease from an affected mother, as it requires contributions from both parents.
Question 3: Which of the following is a specific sign of albinism?
- A. Iris transillumination (Correct Answer)
- B. Sensitivity to light (photophobia)
- C. Involuntary eye movements (nystagmus)
- D. Decreased visual acuity
Explanation: ***Iris transillumination*** - This is a highly **specific sign** of albinism, resulting from the severe reduction or absence of pigment in the iris. - When light shines through the pupil, it passes through the unpigmented iris, creating a visible red reflex, indicating the lack of pigment that normally blocks the light. *Sensitivity to light (photophobia)* - While common in albinism due to the lack of pigment in the iris and retina allowing more light to enter the eye, **photophobia is not specific** to albinism. - It can be a symptom of various other ocular conditions like uveitis, corneal abrasions, or migraines. *Involuntary eye movements (nystagmus)* - **Nystagmus is frequently associated with albinism** due to foveal hypoplasia and impaired visual development but is **not specific**. - It can also be caused by neurological disorders, inner ear problems, or other ocular conditions. *Decreased visual acuity* - **Reduced vision is a characteristic feature of albinism** resulting from foveal hypoplasia and abnormal optic nerve pathways, but it is **not specific** to the condition. - Numerous eye conditions, such as refractive errors, cataracts, and retinal diseases, can lead to decreased visual acuity.
Question 4: Which disease will show the mode of inheritance depicted in this pedigree?
- A. Achondroplasia (Correct Answer)
- B. Prader-Willi syndrome
- C. Wilson disease
- D. Wiskott-Aldrich syndrome
- E. Hemophilia A
Explanation: ***Achondroplasia*** - This pedigree shows an **autosomal dominant** inheritance pattern, characterized by affected individuals in every generation, affected offspring with at least one affected parent, and direct transmission from father to son (which **rules out X-linked**). Achondroplasia is an autosomal dominant disorder. - The presence of **affected individuals (shaded squares/circles)** in each successive generation and the 1:1 ratio of affected to unaffected offspring from affected parents mating with unaffected individuals supports autosomal dominant inheritance. *Prader-Willi syndrome* - This syndrome is caused by **genomic imprinting** or a chromosomal deletion on chromosome 15, typically inherited from the father. It does not follow a simple Mendelian dominant or recessive inheritance pattern. - While it has a genetic basis, its inheritance pattern is **complex** and involves specific parental origin of the genetic defect, unlike the clear autosomal dominant pattern shown. *Wilson disease* - Wilson disease is an **autosomal recessive** disorder, meaning affected individuals inherit two copies of the mutated gene (one from each parent). - This pedigree does not show skipped generations or unaffected parents having affected offspring, which would be characteristic of **autosomal recessive** inheritance. *Wiskott-Aldrich syndrome* - Wiskott-Aldrich syndrome is an **X-linked recessive** disorder. This means it primarily affects males, and affected fathers cannot pass the trait to their sons. - The pedigree shows **affected females** (shaded circles) and **father-to-son transmission** (e.g., father in second generation to son in third generation, assuming the leftmost branch is the paternal line), which rules out X-linked inheritance. *Hemophilia A* - Hemophilia A is an **X-linked recessive** disorder affecting the Factor VIII gene, predominantly affecting males. - Similar to Wiskott-Aldrich syndrome, the presence of **father-to-son transmission** in the pedigree rules out X-linked inheritance patterns, as affected fathers cannot pass X-linked traits to their sons.
Question 5: A patient presents with headache, confusion, and a diagnosis of a brain tumor. The family history reveals brain and kidney tumors. What is the most likely diagnosis?
- A. Neurofibromatosis
- B. Li-Fraumeni syndrome
- C. VHL syndrome (Correct Answer)
- D. Churg-Strauss syndrome
Explanation: ***VHL syndrome*** - **Von Hippel-Lindau (VHL) syndrome** is an inherited disorder characterized by the growth of tumors and cysts in various parts of the body, including the **brain (hemangioblastomas)** and **kidneys (renal cell carcinoma)**. - The presentation of a brain tumor, kidney tumors, and a positive family history for both organs strongly points to VHL syndrome. *Neurofibromatosis* - **Neurofibromatosis (NF)** typically presents with **cafe-au-lait spots**, neurofibromas, optic gliomas, and Lisch nodules. - While it involves brain tumors, kidney tumors are not a primary feature of NF. *Li-Fraumeni syndrome* - **Li-Fraumeni syndrome** is associated with an increased risk of various cancers, including **sarcomas**, **breast cancer**, **adrenocortical carcinomas**, and **leukemia**. - While brain tumors can occur, the specific combination of brain and kidney tumors with a clear family history is less characteristic of Li-Fraumeni than VHL syndrome. *Churg-Strauss syndrome* - **Churg-Strauss syndrome (Eosinophilic Granulomatosis with Polyangiitis)** is a systemic vasculitis characterized by **asthma**, **eosinophilia**, and **granulomatous inflammation**. - It does not involve the development of brain or kidney tumors.
Question 6: What is the cause of glaucoma in retinoblastoma?
- A. Neovascularisation (Correct Answer)
- B. Mass effect of the tumour
- C. Blockage of trabecular network
- D. Lysis of the lens
Explanation: ***Neovascularisation*** - Retinoblastoma leads to **neovascularization of the iris (NVI)** and **angle structures** due to tumor necrosis, ischemia, and release of **angiogenic factors (VEGF)**. - The **neovascular membrane** grows over and obstructs the **trabecular meshwork** and anterior chamber angle, causing **secondary neovascular glaucoma**. - This is the **most characteristic and common mechanism** of glaucoma in advanced retinoblastoma. - Neovascular glaucoma in retinoblastoma is typically **refractory to medical treatment** and indicates poor prognosis. *Blockage of trabecular network* - While tumor cells can directly seed into the anterior chamber and block the trabecular meshwork, this mechanism is **less common** than neovascularization. - This option is also **less specific** as it doesn't identify the underlying pathophysiological process (neovascularization) that is characteristic of retinoblastoma-associated glaucoma. - Direct trabecular blockage by tumor cells typically occurs in advanced disease and often coexists with neovascularization. *Mass effect of the tumour* - The tumor mass itself rarely causes glaucoma through direct mechanical compression of outflow pathways. - Retinoblastoma causes glaucoma primarily through **secondary mechanisms** such as inflammation, neovascularization, or cellular seeding, not simple bulk effect. - Massive tumors may cause angle closure, but this is uncommon compared to neovascular mechanisms. *Lysis of the lens* - **Phacolytic glaucoma** from lens protein leakage is rare in retinoblastoma. - While lens damage can occur with advanced tumors, it is **not a typical or characteristic cause** of glaucoma in retinoblastoma. - The primary mechanisms involve the **tumor-angle-trabecular meshwork axis**, not lens pathology.
Question 7: What is the most common type of congenital cataract?
- A. Blue dot (Correct Answer)
- B. Capsular
- C. Coralliform
- D. Zonular
Explanation: ***Blue dot*** - **Blue dot (punctate) cataracts** are the **most common type of congenital cataract overall**. - They appear as **multiple small, blue-white opacities** scattered throughout the lens cortex. - These cataracts are typically **bilateral, non-progressive, and asymptomatic**, rarely affecting visual acuity. - Often considered **physiological variants**, they usually do not require surgical intervention. *Zonular (Lamellar)* - **Zonular (lamellar) cataracts** are the **most common visually significant** congenital cataract. - They feature **opacities arranged in layers or lamellae** within the lens, classically with alternating clear and opaque zones. - Unlike blue dot cataracts, these **often require surgical intervention** due to visual impairment. *Capsular* - **Capsular cataracts** involve the anterior or posterior lens capsule and are relatively uncommon. - They appear as **small, well-circumscribed opacities** on the lens capsule. - Visual impact depends on size and location relative to the visual axis. *Coralliform* - **Coralliform cataracts** are a rare type characterized by **coral-like branching opacities**. - This distinctive morphology makes them one of the less common congenital cataract types.
Question 8: A 30-year-old female presents with night blindness and peripheral vision loss. Likely diagnosis?
- A. Retinitis pigmentosa (Correct Answer)
- B. Macular degeneration
- C. Glaucoma
- D. Cataract
Explanation: ***Retinitis pigmentosa*** - This condition is characterized by **progressive degeneration of photoreceptor cells**, particularly **rods**, leading to **night blindness (nyctalopia)** and gradual **peripheral vision loss**. - Often leads to a characteristic **'tunnel vision'** due to the progressive loss of the outer visual field. *Macular degeneration* - Primarily affects **central vision**, leading to difficulty with tasks like reading and recognizing faces, rather than night blindness or peripheral loss. - It involves the **degeneration of the macula**, which is responsible for sharp, detailed central vision. *Glaucoma* - Causes gradual **peripheral vision loss** and can lead to **tunnel vision**, but typically does not cause night blindness as its primary symptom. - Results from **damage to the optic nerve**, often due to increased intraocular pressure. *Cataract* - Causes **clouding of the eye's natural lens**, leading to blurry vision, glare, and dulled colors. - It does not typically present with specific night blindness or peripheral vision loss but rather a general decrease in visual acuity.
Question 9: Cataracts and PDA in a newborn suggests in utero infection with which viral family?
- A. Togavirus (Correct Answer)
- B. Adenovirus
- C. Paramyxovirus
- D. Picornavirus
Explanation: ***Togavirus*** is the correct answer. **Congenital rubella syndrome**, caused by the **rubella virus** (family Togaviridae), is classically associated with the triad of **cataracts**, **patent ductus arteriosus (PDA)**, and **sensorineural hearing loss**. The virus crosses the placenta and can cause widespread damage to the developing fetus, particularly during the first trimester when organogenesis occurs. *Adenovirus* is incorrect. Adenoviruses typically cause respiratory tract infections, conjunctivitis, and gastroenteritis in newborns, but are not known to cause congenital abnormalities like cataracts and PDA. While they can infect newborns, their presentation does not include the specific congenital malformations seen with rubella. *Paramyxovirus* is incorrect. The Paramyxovirus family includes viruses like measles and mumps, which can cause severe infections but are not typically associated with congenital cataracts and PDA. Measles can lead to complications in pregnancy such as preterm birth or miscarriage, but not the specific triad of congenital rubella syndrome. *Picornavirus* is incorrect. The Picornavirus family includes enteroviruses (like poliovirus, coxsackievirus) and rhinovirus. While some enteroviruses can cause severe systemic infections in newborns (e.g., myocarditis with coxsackievirus), they are not primarily associated with cataracts and PDA as congenital anomalies.
Question 10: A 10-year-old child presents with inward turning of the right eye, and examination shows limited abduction of the affected eye. What is the most likely diagnosis?
- A. Concomitant strabismus
- B. Paralytic squint (Correct Answer)
- C. Exotropia
- D. Hypertropia
Explanation: ***Paralytic squint*** - The key finding is an **inward turning of the right eye** (**esotropia**) combined with **limited abduction** of that eye, strongly suggesting paralysis or weakness of the **lateral rectus muscle**. - A paralytic squint is characterized by an **underacting extraocular muscle**, leading to a deviation that varies with the direction of gaze and often results in **diplopia** (double vision) and a compensatory head turn. *Concomitant strabismus* - In concomitant strabismus, the **degree of ocular deviation is constant** in all directions of gaze, and there is no limitation of eye movement. - It typically results from an **imbalance in the binocular visual system** rather than a muscle paralysis. *Exotropia* - **Exotropia** refers to an **outward turning of the eye**, which is the opposite of the inward turning (**esotropia**) described in the clinical presentation. - While it is a type of strabismus, its direction of deviation does not match the patient's symptoms. *Hypertropia* - **Hypertropia** is an **upward deviation of one eye**, meaning the affected eye is higher than the other. - This condition is also not consistent with the reported inward turning of the eye.
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