Albinism — MCQs
Arcuate field defect akin to glaucoma is seen in?
Which of the following is a specific sign of albinism?
Which one of the following is an autosomal recessive disorder?
Target or iris lesions are seen in:
Which one of the following is an autosomal dominant disorder?
A 76-year-old female presents with difficulty reading. Bilateral white opacifications consistent with cataract formation are observed. In which structure are these opacifications located?
A patient presents with the skin finding shown in the image. Identify the most likely diagnosis for this lesion.
What is the most common association with Acanthosis nigricans?
Defect seen in Vitiligo is:
An increased incidence of vitiligo is found in association with which of the following conditions?
Albinism Indian Medical PG Practice Questions and MCQs
Question 1: Arcuate field defect akin to glaucoma is seen in?
- A. Optic nerve lesion (Correct Answer)
- B. Pituitary adenoma
- C. Posterior cerebral artery infarct
- D. None of the options
Explanation: ***Optic nerve lesion*** - An **arcuate field defect** is a specific pattern of visual field loss that follows the course of nerve fibers in the retina and is characteristic of **optic nerve damage**, similar to what is seen in glaucoma. - This type of defect is due to damage to the **bundle of retinal nerve fibers** that arch above or below the macula, often causing a scotoma (blind spot) that respects the horizontal meridian. - Common causes include **anterior ischemic optic neuropathy (AION)**, **optic neuritis**, and other optic nerve pathologies that affect the nerve fiber layer. *Pituitary adenoma* - A pituitary adenoma typically causes a **bitemporal hemianopsia** due to compression of the optic chiasm. - This visual field defect involves the lateral halves of both visual fields, which is different from an arcuate defect. *Posterior cerebral artery infarct* - An infarct in the posterior cerebral artery typically leads to a **homonymous hemianopsia** (loss of half of the visual field on the same side in both eyes) or a quadrantanopsia. - This type of defect results from damage to the **visual cortex** or optic radiations, not the optic nerve itself in a glaucoma-like pattern. *None of the options* - This is incorrect because **optic nerve lesion** is a valid and correct answer. - Optic nerve pathologies are well-established causes of arcuate field defects similar to those seen in glaucoma.
Question 2: 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 3: Which one of the following is an autosomal recessive disorder?
- A. Albinism (Correct Answer)
- B. Marfan’s syndrome
- C. Neurofibromatosis-1
- D. Huntington's disease
Explanation: ***Albinism*** - **Albinism** is an **autosomal recessive disorder** characterized by a partial or complete lack of melanin pigment in the skin, hair, and eyes [1], [2]. - This condition is inherited when an individual receives **two copies of the defective gene**, one from each parent [1]. *Huntington's disease* - **Huntington's disease** is an **autosomal dominant disorder**, meaning only one copy of the mutated gene is sufficient to cause the disease. - It is characterized by progressive neurodegeneration, leading to uncontrolled movements, cognitive decline, and psychiatric problems. *Marfan's syndrome* - **Marfan's syndrome** is an **autosomal dominant disorder** affecting connective tissue, primarily impacting the skeletal, ocular, and cardiovascular systems. - It results from a mutation in the **FBN1 gene** which encodes for fibrillin-1, a component of elastic fibers. *Neurofibromatosis-1* - **Neurofibromatosis type 1 (NF1)** is an **autosomal dominant disorder** caused by a mutation in the NF1 gene, leading to the growth of tumors along nerves. - Clinical features include **café-au-lait spots**, neurofibromas, and Lisch nodules. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 150-151. [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. 119-120.
Question 4: Target or iris lesions are seen in:
- A. Erythema multiforme (Correct Answer)
- B. Urticaria
- C. Scabies
- D. Lichen planus
Explanation: ***Erythema multiforme*** - Erythema multiforme is characterized by **target lesions** (also known as iris lesions), which are concentric rings of color resembling a bull's-eye. - These lesions typically have a **dusky center**, a paler edematous ring, and an outer erythematous halo. *Urticaria (hives)* - Urticaria presents with **pruritic, transient wheals** (hives) that are typically erythematous and edematous, but they do not form target or iris patterns. - The lesions in urticaria are often **blanchable** and migrate rapidly. *Scabies (itch mite infestation)* - Scabies manifests as **intensely pruritic papules, vesicles, and burrows**, often found in web spaces of fingers, wrists, and genitalia. - It does not produce target lesions; burrows are a **pathognomonic sign**. *Lichen planus (inflammatory skin condition)* - Lichen planus characteristically presents with **pruritic, polygonal, purple, planar papules and plaques** (the 6 P's). - It may also show **Wickham's striae** (fine white lines on the surface), but it does not form target-like lesions.
Question 5: Which one of the following is an autosomal dominant disorder?
- A. Cystic fibrosis
- B. Hereditary spherocytosis (Correct Answer)
- C. Sickle cell anemia
- D. G-6PD deficiency
Explanation: ***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].
Question 6: A 76-year-old female presents with difficulty reading. Bilateral white opacifications consistent with cataract formation are observed. In which structure are these opacifications located?
- A. Aqueous humor
- B. Cornea
- C. Lens (Correct Answer)
- D. Optic nerve
Explanation: ***Lens*** - **Cataracts** are defined by the **clouding of the natural lens** of the eye, which causes blurred vision and difficulty with activities like reading. - The condition is very common, especially among older adults, and affects the **bilateral vision** as described in the case. *Aqueous humor* - The **aqueous humor** is a clear fluid that fills the space between the cornea and the lens; it is not the structure that becomes opaque in cataracts. - Problems with aqueous humor are typically associated with glaucoma (due to increased intraocular pressure) rather than cataract formation. *Cornea* - The **cornea** is the transparent outer layer of the eye that helps focus light, but it does not develop cataracts. - Opacities in the cornea (e.g., from injuries or infections) would be described differently and produce different visual symptoms. *Optic nerve* - The **optic nerve** transmits visual information from the retina to the brain; it is a nerve, not a structure where light focuses or where cataracts develop. - Damage to the optic nerve typically leads to vision loss or blind spots, not blurred vision from opacification.
Question 7: A patient presents with the skin finding shown in the image. Identify the most likely diagnosis for this lesion.
- A. Vitiligo
- B. Contact leukoderma
- C. Piebaldism (Correct Answer)
- D. Albinism
Explanation: ***Piebaldism*** - The image shows a **localized patch of depigmentation** on the forehead, characteristic of **piebaldism**. - **Piebaldism** is a rare, congenital autosomal dominant disorder caused by a defect in melanocyte development and migration, resulting in stable, well-demarcated depigmented areas, often with a **white forelock**. *Vitiligo* - **Vitiligo** typically presents as **progressive, acquired macules and patches of depigmentation** that often enlarge over time. - While it can appear on the face, the sharply demarcated, congenital appearance seen here is more consistent with piebaldism. *Contact leukoderma* - **Contact leukoderma** is an **acquired depigmentation** resulting from exposure to chemicals (e.g., rubber, phenols). - It would usually present in areas of direct contact, and the congenital nature of the lesion in the image rules this out. *Albinism* - **Albinism** is a **generalized hypopigmentation** affecting the skin, hair, and eyes due to a defect in melanin production. - The image shows a localized patch of depigmentation, not a widespread lack of pigment characteristic of albinism.
Question 8: What is the most common association with Acanthosis nigricans?
- A. Hypertension
- B. Diabetes Mellitus
- C. Obesity (Correct Answer)
- D. Hypothyroidism
Explanation: **Explanation:** **Acanthosis Nigricans (AN)** is a common dermatological condition characterized by hyperpigmented, velvety plaques, typically found in intertriginous areas like the axilla and neck. **Why Obesity is the Correct Answer:** Obesity is the **most common** association and cause of Acanthosis Nigricans (Pseudo-acanthosis nigricans). The underlying mechanism is **Insulin Resistance**. In obese individuals, high levels of circulating insulin bind to **Insulin-like Growth Factor-1 (IGF-1) receptors** on keratinocytes and fibroblasts. This stimulates excessive proliferation of these cells, leading to the characteristic epidermal thickening and hyperpigmentation. **Analysis of Incorrect Options:** * **Diabetes Mellitus (B):** While AN is a strong cutaneous marker for Type 2 Diabetes, it usually precedes the clinical onset of diabetes. Obesity remains the primary driver and more frequent association. * **Hypertension (A) & Hypothyroidism (D):** These are often part of the "Metabolic Syndrome" or associated endocrinopathies (like PCOS), but they are not the primary or most common cause of the skin changes seen in AN. **High-Yield Clinical Pearls for NEET-PG:** * **Malignant Acanthosis Nigricans:** If AN appears suddenly, is very extensive, or involves the palms (**Tripe Palms**) and oral mucosa, it is highly suggestive of internal malignancy, most commonly **Gastric Adenocarcinoma**. * **Histopathology:** Shows hyperkeratosis and papillomatosis. Note that "acanthosis" (thickening of the stratum spinosum) is actually minimal despite the name. * **Common Sites:** Neck (most common), axilla, groins, and knuckles. * **Drug-induced AN:** Can be caused by Nicotinic acid, systemic corticosteroids, and OCPs.
Question 9: Defect seen in Vitiligo is:
- A. Absent melanosomes
- B. Absent melanocytes (Correct Answer)
- C. Reduction in melanin synthesis
- D. Reduction in number of melanocytes
Explanation: **Explanation:** **Vitiligo** is an acquired, chronic pigmentary disorder characterized by the selective destruction of melanocytes. **1. Why Option B is correct:** The hallmark of vitiligo is the **complete absence of functional melanocytes** in the affected skin. This is primarily due to an autoimmune-mediated destruction where T-cells target melanocyte-specific antigens. Histopathologically, a skin biopsy of a stable vitiligo lesion shows a total lack of melanocytes (DOPA-negative) and a consequent absence of melanin in the epidermis. **2. Why other options are incorrect:** * **Option A (Absent melanosomes):** This is seen in **Chediak-Higashi syndrome** or specific trafficking defects. In vitiligo, the "factory" (melanocyte) is gone, so melanosomes are naturally absent, but the primary defect is the cell loss itself. * **Option C (Reduction in melanin synthesis):** This describes **Albinism**, where melanocytes are present in normal numbers, but there is a genetic defect in the enzyme tyrosinase, leading to decreased melanin production. * **Option D (Reduction in number of melanocytes):** This describes **Nevus Depigmentosus** or **Pityriasis Alba**, where melanocytes are present but decreased in number or activity. In vitiligo, the loss is absolute in the lesion. **High-Yield Clinical Pearls for NEET-PG:** * **Most common association:** Autoimmune thyroid disease (Hashimoto’s). * **Koebner Phenomenon:** Vitiligo is Koebner positive (new lesions at sites of trauma). * **Segmental Vitiligo:** Does not follow the Koebner phenomenon and has a dermatomal distribution. * **Treatment of Choice:** Narrowband UVB (NB-UVB) is the gold standard for generalized vitiligo. * **Wood’s Lamp:** Lesions show a characteristic **"milky white"** fluorescence.
Question 10: An increased incidence of vitiligo is found in association with which of the following conditions?
- A. Psoriasis
- B. Nutritional deficiency
- C. Old age
- D. Diabetes mellitus (Correct Answer)
Explanation: **Explanation:** **Vitiligo** is a chronic autoimmune skin disorder characterized by the destruction of melanocytes. The key medical concept to understand for NEET-PG is that vitiligo is frequently associated with other **organ-specific autoimmune disorders**. **1. Why Diabetes Mellitus is correct:** Vitiligo is part of a spectrum of autoimmune polyendocrine syndromes. There is a statistically significant association between vitiligo and **Type 1 Diabetes Mellitus** (and occasionally Type 2) due to shared genetic susceptibility and autoimmune pathways. Other common associations include: * **Thyroid disorders** (most common association, especially Hashimoto’s thyroiditis). * Pernicious anemia. * Addison’s disease. * Alopecia areata. **2. Why the other options are incorrect:** * **Psoriasis (A):** While both are T-cell mediated inflammatory skin diseases, psoriasis is not classically associated with the systemic autoimmune cluster seen in vitiligo. * **Nutritional deficiency (B):** Vitiligo is an autoimmune process, not a nutritional one. While some studies suggest low Vitamin B12 or Vitamin D levels in vitiligo patients, deficiency is not a causative or strongly associated factor. * **Old age (C):** Vitiligo typically has an early onset; 50% of cases begin before age 20. It is not a degenerative condition of aging. **High-Yield Clinical Pearls for NEET-PG:** * **Most common association:** Thyroid dysfunction (check TSH in vitiligo patients). * **Koebner Phenomenon:** Vitiligo shows positivity (depigmentation at sites of trauma). * **Vogt-Koyanagi-Harada Syndrome:** Vitiligo associated with uveitis, meningitis, and auditory symptoms. * **Treatment of choice:** Narrowband UVB (NB-UVB) is the gold standard for generalized vitiligo.
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