Disorders of Pigmentation — MCQs
A 45-year-old man presents with the following skin changes (as shown in the image). What relevant history should be taken to diagnose this condition?
Patient with pigmented skin lesion shows pagetoid spread of atypical melanocytes. Diagnosis?
An infant presented with vomiting, malnutrition, blue eyes, blonde hair & fair skin. On investigation, Guthrie test was positive. All are true regarding this disease EXCEPT:
Wood's lamp is used in the diagnosis of:
A 35-year-old woman consulted a dermatologist due to a persistent facial rash. Physical examination revealed an erythematous rash, without blistering or ulceration, involving both cheeks and the nose, with the nasolabial folds relatively spared. The dermatologist also noted scattered erythematous, firm, maculopapular lesions on the face, neck, upper chest, and elbows, as well as focal alopecia on the scalp. The patient reported that the rash had been present for approximately six months, with exacerbation upon exposure to sunlight. Which autoimmune disease would MOST likely produce this patient's skin problems?
A 77-year-old man has a lesion on the right side of his face that has enlarged slowly over the past 5 years. On examination, the 3-cm lesion has irregular borders, irregular brown to black pigmentation, and a central 2-mm raised blue-black nodule. The lesion is resected and microscopically shows radial growth of large round malignant cells, some isolated and others in nests in the epidermis and superficial papillary dermis. The cells have prominent red nucleoli and dust-like cytoplasmic pigment. Which mutated gene is most likely to be present in the skin lesion of this man?
In alkaptonuria, deficiency is:
Langerhans cells in skin are :
Langerhans cells in skin fall under which category?
Which of the following genetic syndromes are associated with brain tumours? 1. Neurofibromatosis type 1 2. Neurofibromatosis type 2 3. Tuberous sclerosis 4. Wiskott-Aldrich syndrome Select the answer using the code given below.
Disorders of Pigmentation Indian Medical PG Practice Questions and MCQs
Question 1: A 45-year-old man presents with the following skin changes (as shown in the image). What relevant history should be taken to diagnose this condition?
- A. Dementia
- B. History of dietary pattern, dementia, and diarrhea (Correct Answer)
- C. Dietary history
- D. Depression
Explanation: ***History of dietary pattern, dementia, and diarrhea*** - The image displays skin changes consistent with a "Casal's necklace" pattern, characteristic of **pellagra**, a disease caused by **niacin (Vitamin B3) deficiency**. - Pellagra is classically associated with the "3 Ds": **dermatitis** (the observed skin changes), **diarrhea**, and **dementia**. A comprehensive history should therefore include questions about dietary patterns (especially corn-based diets lacking tryptophan and niacin), gastrointestinal symptoms like diarrhea, and neurological/psychiatric symptoms indicative of dementia. *Dementia* - While **dementia** is one of the classic "3 Ds" of pellagra (niacin deficiency), it is only one component of the presentation and insufficient on its own to guide a complete diagnostic history for this condition. - Focusing solely on dementia would miss crucial aspects like dietary intake and gastrointestinal symptoms that are integral to diagnosing pellagra. *Dietary history* - A **dietary history** is indeed very relevant for diagnosing pellagra, as it helps identify potential niacin deficiency, commonly associated with diets heavily reliant on corn without proper preparation. - However, pellagra is not only characterized by dermatological signs and dietary insufficiency but also by gastrointestinal and neurological symptoms. Limiting the history to diet alone would therefore be incomplete. *Depression* - **Depression** can be a symptom of various nutritional deficiencies and other medical conditions, but it is not one of the classic "3 Ds" of pellagra, which are dermatitis, diarrhea, and dementia. - While mood changes might be present in some patients with niacin deficiency, focusing solely on depression would not encompass the full clinical picture of pellagra and could lead to misdiagnosis.
Question 2: Patient with pigmented skin lesion shows pagetoid spread of atypical melanocytes. Diagnosis?
- A. Lentigo maligna
- B. Superficial spreading melanoma (Correct Answer)
- C. Blue nevus
- D. Nodular melanoma
Explanation: ### Superficial spreading melanoma - This is the most common type of melanoma and is characterized by a **radial growth phase** where atypical melanocytes spread along the **dermo-epidermal junction** and into the epidermis (pagetoid spread) [1]. - **Pagetoid spread**, referring to the upward migration of atypical melanocytes into the spinous and granular layers of the epidermis, is a hallmark histological feature. *Lentigo maligna* - This is a melanoma subtype primarily affecting **chronically sun-damaged skin** in older individuals, typically on the face. - While it has a prolonged **radial growth phase**, the atypical melanocytes tend to be confined to the **basal layer** and do not typically exhibit prominent pagetoid spread like superficial spreading melanoma. *Blue nevus* - A blue nevus is a **benign melanocytic lesion** characterized by the presence of dermal melanocytes that produce melanin deep within the dermis, giving it a characteristic blue or blue-gray color [2]. - It does not involve **atypical melanocytes** or **pagetoid spread** (upward migration of cells into the epidermis). *Nodular melanoma* - This is an aggressive subtype of melanoma characterized by a rapid **vertical growth phase** and minimal or absent radial growth phase [1]. - It presents as a **dark, raised nodule** and typically lacks the prominent pagetoid spread seen in the superficial spreading type, as its growth is primarily downward into the dermis. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, pp. 1151-1152. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, p. 1146.
Question 3: An infant presented with vomiting, malnutrition, blue eyes, blonde hair & fair skin. On investigation, Guthrie test was positive. All are true regarding this disease EXCEPT:
- A. Phenyl acetate positive in urine
- B. Mental retardation is present
- C. Hypopigmentation due to tryptophan deficiency (Correct Answer)
- D. Due to PAH enzyme defect
Explanation: ***Hypopigmentation due to tryptophan deficiency*** - The characteristic **hypopigmentation** (fair skin, blonde hair, blue eyes) in **phenylketonuria (PKU)** is due to **tyrosine deficiency**, not tryptophan deficiency. - **Phenylalanine hydroxylase (PAH)** deficiency leads to accumulation of phenylalanine, which cannot be converted to **tyrosine**. - **Tyrosine** is the precursor for **melanin synthesis** via the enzyme **tyrosinase**, so tyrosine deficiency results in decreased melanin production and hypopigmentation. *Phenyl acetate positive in urine* - In **phenylketonuria (PKU)**, **phenylalanine** accumulates and is shunted to alternative metabolic pathways, leading to the production and excretion of **phenylacetate, phenylpyruvate, and phenyllactate** in the urine. - The presence of these metabolites gives the urine a characteristic **mousey or musty odor**. *Mental retardation is present* - If **phenylketonuria (PKU)** is left untreated, the accumulation of **phenylalanine** is neurotoxic and leads to severe, **irreversible intellectual disability** and **developmental delay**. - Early detection through newborn screening (the **Guthrie test** detects elevated blood phenylalanine) and dietary phenylalanine restriction are crucial to prevent this outcome. *Due to PAH enzyme defect* - **Phenylketonuria (PKU)** is primarily caused by a deficiency in the enzyme **phenylalanine hydroxylase (PAH)**, which is responsible for converting phenylalanine to tyrosine. - This **autosomal recessive genetic disorder** leads to the accumulation of phenylalanine in the blood and tissues, causing the clinical manifestations.
Question 4: Wood's lamp is used in the diagnosis of:
- A. P. versicolor
- B. Vitiligo
- C. Porphyria
- D. All of the options (Correct Answer)
Explanation: ***All of the options*** - Wood's lamp is a diagnostic tool that uses **ultraviolet light (UV-A at 365 nm)** to detect certain skin conditions by observing characteristic fluorescence patterns. - All three conditions listed show distinctive features under Wood's lamp examination, making this an important diagnostic tool in dermatology. **P. versicolor (Pityriasis versicolor)** - Shows characteristic **yellow-green to golden-orange fluorescence** under Wood's lamp - This fluorescence is due to metabolites produced by *Malassezia* yeast species - Helps confirm diagnosis and delineate the extent of lesions, especially on darker skin **Vitiligo** - Depigmented areas appear as **bright, stark white patches** with sharp borders under UV light - Wood's lamp accentuates areas of **complete melanin loss**, making subtle lesions more visible - Particularly useful for detecting vitiligo on fair skin where lesions may not be clinically apparent - Helps differentiate vitiligo from other hypopigmented conditions **Porphyria** - In **porphyria cutanea tarda (PCT)** and **congenital erythropoietic porphyria (CEP)**, Wood's lamp detects **coral-red to pink-orange fluorescence** - Fluorescence is seen in urine (containing porphyrins), teeth, and sometimes skin lesions - This occurs due to accumulation of **porphyrins**, which are photosensitive compounds that fluoresce under UV light - Useful screening tool for suspected porphyria cases
Question 5: A 35-year-old woman consulted a dermatologist due to a persistent facial rash. Physical examination revealed an erythematous rash, without blistering or ulceration, involving both cheeks and the nose, with the nasolabial folds relatively spared. The dermatologist also noted scattered erythematous, firm, maculopapular lesions on the face, neck, upper chest, and elbows, as well as focal alopecia on the scalp. The patient reported that the rash had been present for approximately six months, with exacerbation upon exposure to sunlight. Which autoimmune disease would MOST likely produce this patient's skin problems?
- A. Dermatomyositis
- B. Progressive systemic sclerosis
- C. Systemic lupus erythematosus (Correct Answer)
- D. Rheumatoid arthritis
Explanation: ***Systemic lupus erythematosus*** - The **malar rash** (sparing the nasolabial folds) and photosensitivity are classic dermatological findings in **systemic lupus erythematosus (SLE)**. - **Focal alopecia** and other **maculopapular lesions** are also characteristic skin manifestations of SLE. *Dermatomyositis* - While dermatomyositis can also present with photosensitive rashes, the typical facial involvement includes **heliotrope rash** around the eyes or **Gottron's papules** over bony prominences. - The description of a malar rash sparing nasal folds and scattered maculopapular lesions is less consistent with dermatomyositis. *Progressive systemic sclerosis* - This condition is primarily characterized by **skin thickening and hardening** (scleroderma), often starting in the extremities and face. - The described **erythematous rash** with separate maculopapular lesions and alopecia is not typical for progressive systemic sclerosis. *Rheumatoid arthritis* - Rheumatoid arthritis is a chronic inflammatory joint disease and does **not typically present with primary dermatological manifestations** like the facial rash, photosensitivity, or alopecia described. - While some skin findings can occur (e.g., rheumatoid nodules), they are not the prominent features described.
Question 6: A 77-year-old man has a lesion on the right side of his face that has enlarged slowly over the past 5 years. On examination, the 3-cm lesion has irregular borders, irregular brown to black pigmentation, and a central 2-mm raised blue-black nodule. The lesion is resected and microscopically shows radial growth of large round malignant cells, some isolated and others in nests in the epidermis and superficial papillary dermis. The cells have prominent red nucleoli and dust-like cytoplasmic pigment. Which mutated gene is most likely to be present in the skin lesion of this man?
- A. ATM
- B. BRAF (Correct Answer)
- C. NF1
- D. TYR
Explanation: ***BRAF*** - The presence of **irregular pigmentation** and characteristics of melanoma suggest an association with mutations, particularly in the **BRAF gene**, often seen in **cutaneous melanoma** [1,2]. - BRAF mutations are commonly involved in **cell proliferation** and survival pathways that contribute to the malignant behavior of melanoma cells [1]. *TYR* - TYR (tyrosinase) is primarily involved in **melanin synthesis** and is not directly implicated in melanoma pathogenesis. - Although mutations may affect pigmentation, they do not correlate with increased tumorigenicity seen in melanoma. *ATM* - ATM (Ataxia Telangiectasia Mutated) is related to **DNA repair mechanisms** and is more associated with predisposition to **other cancers** rather than directly involved with melanoma. - It does not account for the specific features of **BRAF mutation** in melanoma progression. *NF1* - NF1 (Neurofibromatosis type 1) mutations are associated with neurofibromas and possibly with a predisposition to certain types of **malignancies**, but not primarily to **melanomas**. - The clinical presentation does not support an NF1 mutation considering the distinct features of the lesion described. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, pp. 1150-1151. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, pp. 1152-1153.
Question 7: In alkaptonuria, deficiency is:
- A. Phosphofructokinase
- B. HMG CoA reductase
- C. Homogentisate oxidase (Correct Answer)
- D. Xanthine oxidase
Explanation: ***Homogentisate oxidase*** - **Alkaptonuria** is an autosomal recessive disorder caused by a deficiency of the enzyme **homogentisate 1,2-dioxygenase** (also known as homogentisate oxidase). - This enzyme is crucial in the **catabolic pathway of tyrosine**, specifically breaking down **homogentisic acid**. *Phosphofructokinase* - Deficiency of **phosphofructokinase** (PFK) causes **Tarui's disease** (Glycogen Storage Disease Type VII), affecting **glycolysis**. - Symptoms include exercise intolerance, muscle pain, and hemolysis, which are unrelated to alkaptonuria. *HMG CoA reductase* - **HMG-CoA reductase** is the rate-limiting enzyme in **cholesterol biosynthesis**, and its inhibitors (statins) are used to lower cholesterol levels. - Its deficiency is not associated with alkaptonuria. *Xanthine oxidase* - **Xanthine oxidase** is involved in the catabolism of **purines**, converting hypoxanthine to xanthine and then xanthine to uric acid. - Its deficiency causes **xanthinuria**, leading to kidney stones, and it is not associated with alkaptonuria.
Question 8: Langerhans cells in skin are :
- A. Antigen presenting cells (Correct Answer)
- B. Sensory neurons
- C. Pigment producing cells
- D. Keratin synthesizing cells
Explanation: ***Antigen presenting cells*** - Langerhans cells are specialized **dendritic cells** found in the epidermis, functioning as crucial **antigen-presenting cells (APCs)** [1], [2]. - They **phagocytose antigens** in the skin, process them, and then migrate to lymph nodes to present the antigens to **T lymphocytes**, initiating an immune response [1]. *Keratin synthesizing cells* - **Keratinocytes** are the primary cells responsible for synthesizing **keratin** and forming the protective barrier of the epidermis [2]. - Langerhans cells originate from the bone marrow and are not involved in structural protein synthesis. *Sensory neurons* - **Merkel cells** and **free nerve endings** are the primary sensory structures found in the skin, responsible for touch, pressure, temperature, and pain sensation [2]. - Langerhans cells are immune cells, not nerve cells. *Pigment producing cells* - **Melanocytes** are the cells responsible for producing **melanin**, the pigment that provides skin color and protects against UV radiation [2]. - Langerhans cells do not produce melanin. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, p. 200. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, p. 1144.
Question 9: Langerhans cells in skin fall under which category?
- A. Keratin synthesising cell
- B. Sensory neurons
- C. Pigment producing cells
- D. Antigen presenting cell (Correct Answer)
Explanation: ***Antigen presenting cell*** - **Langerhans cells** are specialized **dendritic cells** found in the epidermis of the skin and play a crucial role in the immune system [1], [3]. - Their primary function is to capture and process antigens from the skin environment and present them to **T lymphocytes**, initiating an immune response [1], [2]. *Keratin synthesising cell* - **Keratinocytes** are the primary cells responsible for synthesizing **keratin**, providing structural integrity to the epidermis [3]. - Langerhans cells originate from bone marrow and are not involved in keratin production. *Sensory neurons* - **Sensory neurons** (e.g., Merkel cells and nerve endings) are responsible for transmitting sensations like touch, pressure, and pain [3]. - Langerhans cells are immune cells and do not have neuronal functions. *Pigment producing cells* - **Melanocytes** are the cells responsible for producing **melanin**, the pigment that gives skin, hair, and eyes their color [3]. - Langerhans cells do not produce pigment; their role is immune surveillance [3]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, p. 200. [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. 174-175. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, p. 1144.
Question 10: Which of the following genetic syndromes are associated with brain tumours? 1. Neurofibromatosis type 1 2. Neurofibromatosis type 2 3. Tuberous sclerosis 4. Wiskott-Aldrich syndrome Select the answer using the code given below.
- A. 1, 2 and 3 (Correct Answer)
- B. 1, 3 and 4
- C. 1 and 2 only
- D. 2, 3 and 4
Explanation: ***1, 2 and 3*** - **Neurofibromatosis type 1 (NF1)**, **Neurofibromatosis type 2 (NF2)**, and **Tuberous sclerosis (TSC)** are all well-established genetic syndromes associated with an increased risk of developing various brain tumors [1]. - NF1 is linked to **optic pathway gliomas**, NF2 to **schwannomas** and **meningiomas**, and TSC to **subependymal giant cell astrocytomas (SEGAs)** [1], [2]. *1 and 2 only* - This option is incomplete as it correctly identifies NF1 and NF2 but omits Tuberous sclerosis, which is also strongly associated with brain tumours [1]. - While NF1 and NF2 are major genetic risk factors for brain tumors, excluding TSC would be an inaccurate representation of conditions linked to these abnormalities [1]. *1, 3 and 4* - This option incorrectly includes **Wiskott-Aldrich syndrome (WAS)**, which is an **immunodeficiency disorder** and not typically associated with primary brain tumours. - Although WAS can lead to an increased risk of lymphomas, these are generally not considered primary brain tumors [1] in the context of genetic syndromes predisposing to such growths. *2, 3 and 4* - This option again incorrectly includes **Wiskott-Aldrich syndrome** while omitting **Neurofibromatosis type 1**, a significant genetic syndrome linked to brain tumors [1]. - Omitting NF1, a condition known for an increased risk of gliomas, renders this option incomplete and inaccurate. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 724-725. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1318-1319.
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free