Basic Dermatology — MCQs

Basic Dermatology Indian Medical PG Practice Questions and MCQs

Question 291: Koebner's phenomenon is seen in all except

A. Psoriasis
B. Warts
C. Tinea corporis (Correct Answer)
D. Molluscum contagiosum

Explanation: ***Tinea corporis*** - **Koebner's phenomenon**, also known as the isomorphic response, is the appearance of skin lesions characteristic of a **pre-existing dermatosis** at sites of **trauma** to previously uninvolved skin. - **Tinea corporis**, a **superficial fungal infection**, does NOT exhibit true Koebner's phenomenon. - Its spread occurs through **direct fungal contact or autoinoculation**, not through an isomorphic response to non-specific trauma. *Psoriasis* - **Psoriasis** is the **classic example** of Koebner's phenomenon. - New psoriatic plaques can appear at sites of **skin trauma** such as scratches, surgical scars, burns, or tattoos within **10-20 days** of injury. - This occurs in approximately **25-50%** of psoriasis patients. *Warts* - **Warts** (verruca vulgaris), caused by **human papillomavirus (HPV)**, can show what is sometimes called **pseudo-Koebner's phenomenon**. - Trauma facilitates **viral inoculation** and seeding of HPV into the skin, leading to new wart formation along scratch lines. - However, this is technically **viral spread through trauma**, not a true isomorphic response of a pre-existing dermatosis. *Molluscum contagiosum* - **Molluscum contagiosum** can similarly demonstrate **pseudo-Koebner's phenomenon**. - Scratching spreads the **molluscum contagiosum virus** to adjacent areas, creating linear arrays of lesions. - Like warts, this represents **direct viral inoculation** rather than true isomorphic response, but is often grouped with Koebner's phenomenon in clinical practice.

Question 292: Phrynoderma is a cutaneous manifestation of severe deficiency of vitamin :

A. Vitamin D
B. Vitamin C
C. Vitamin B
D. Vitamin A (Correct Answer)

Explanation: ***Vitamin A*** - **Phrynoderma**, also known as **toad skin** or follicular hyperkeratosis, is a classic cutaneous manifestation of severe **vitamin A deficiency**. - This condition is characterized by **dry, scaly skin** with prominent **follicular papules** due to hyperkeratosis around hair follicles. *Vitamin D* - Deficiency of **vitamin D** is primarily associated with bone diseases like **rickets** in children and **osteomalacia** in adults. - While it can manifest with diffuse musculoskeletal pain and weakness, it does not typically cause the specific follicular hyperkeratosis seen in phrynoderma. *Vitamin C* - **Vitamin C deficiency** leads to **scurvy**, characterized by **gingivitis**, easy bruising, poor wound healing, and **perifollicular hemorrhages**. - Although it affects skin and hair follicles, the appearance of perifollicular hemorrhages is distinct from the hyperkeratotic papules of phrynoderma. *Vitamin B* - **Vitamin B complex deficiencies** can cause a wide range of dermatological issues, such as **pellagra** (niacin/B3 deficiency) with photosensitive dermatitis, or **cheilosis** and **glossitis** (riboflavin/B2 deficiency). - However, deficiencies in B vitamins do not typically present with phrynoderma or follicular hyperkeratosis as their primary cutaneous manifestation.

Question 293: Loss of lateral 1/3rd of eyebrow is seen in -

A. Tetanus
B. Tinea capitis
C. Lepromatous leprosy (Correct Answer)
D. Tuberculosis

Explanation: ***Lepromatous leprosy*** - **Loss of the lateral one-third of the eyebrow** (also known as **madarosis**) is a characteristic feature of **lepromatous leprosy** due to chronic inflammation and nerve damage affecting hair follicles. - This, along with diffuse skin infiltration and nodule formation, is part of the typical presentation of the **multibacillary form** of the disease. *Tetanus* - Tetanus is characterized by **muscle spasms** and **lockjaw** due to the action of tetanus toxin on inhibitory neurotransmitters. - It does not cause hair loss or specific dermatological lesions like eyebrow loss. *Tinea capitis* - Tinea capitis is a **fungal infection of the scalp** that causes scaling, itching, and patchy hair loss on the head. - It does not typically affect the eyebrows or cause isolated loss of the lateral one-third part. *Tuberculosis* - Tuberculosis primarily affects the **lungs** but can manifest in various extrapulmonary sites. - While systemic symptoms and skin lesions (e.g., **lupus vulgaris**) can occur, **eyebrow loss** is not a characteristic feature of tuberculosis.

Question 294: Erythema nodosum is seen in all of the following except:

A. Tuberculosis
B. Pregnancy
C. Chronic pancreatitis (Correct Answer)
D. SLE

Explanation: ***Chronic pancreatitis*** - **Erythema nodosum** is a **panniculitis**, an inflammation of the subcutaneous fat. **Chronic pancreatitis** is generally NOT a recognized cause of erythema nodosum. - Pancreatic diseases, specifically **acute pancreatitis**, can sometimes cause a different type of panniculitis called **pancreatic panniculitis**, characterized by fat necrosis and enzymatic destruction of subcutaneous fat—this is distinct from erythema nodosum. - Chronic pancreatitis does not have this association with either condition. *Tuberculosis* - **Tuberculosis** is one of the most well-established infectious causes of erythema nodosum, especially in endemic regions. - The cell-mediated immune response to mycobacterial antigens triggers the characteristic tender, red subcutaneous nodules. *Pregnancy* - **Pregnancy** is a well-recognized physiological trigger for erythema nodosum due to hormonal changes and altered immune responses. - It typically occurs in the second trimester and is considered one of the common non-pathological causes. *SLE* - **Systemic lupus erythematosus (SLE)** has been reported in association with erythema nodosum, though this is relatively uncommon. - While SLE has numerous cutaneous manifestations (malar rash, discoid lesions, lupus panniculitis), erythema nodosum can occasionally occur as part of the systemic inflammatory response.

Question 295: On stretching the cheek the lesion disappears in:

A. White sponge nevus
B. Leukoedema (Correct Answer)
C. Focal hyperkeratosis
D. Leukoplakia

Explanation: **Leukoedema** - **Leukoedema** is a common, benign, opalescent whitish-gray lesion of the buccal mucosa that **disappears or becomes less noticeable upon stretching the cheek**. - This characteristic disappearance upon stretching is a key diagnostic feature, differentiating it from other white lesions. - It is a developmental variation seen in up to 90% of African Americans and less commonly in other populations. *White sponge nevus* - **White sponge nevus** is a rare hereditary condition presenting as white, thick, folded plaques on the buccal mucosa bilaterally. - Unlike leukoedema, the lesions **do not disappear on stretching** and persist throughout life. - It is caused by mutations in keratin genes and remains constant in appearance. *Focal hyperkeratosis* - **Focal hyperkeratosis** is a thickened white lesion often caused by chronic irritation or friction, and while it may appear whitish, it **does not disappear or diminish upon stretching** the oral mucosa. - The whiteness is due to an excess of keratin, making it a more fixed and persistent lesion. *Leukoplakia* - **Leukoplakia** is a clinical term for a white patch or plaque on the oral mucosa that **cannot be rubbed off** and **cannot be characterized clinically or pathologically as any other disease**. It does not disappear on stretching. - It is considered a potentially malignant disorder, and its persistence with stretching is a significant differentiator from leukoedema.

Question 296: Acrodermatitis enteropathica is seen with deficiency of?

A. Zinc (Correct Answer)
B. Copper
C. Vitamin A
D. Iron

Explanation: ***Zinc*** - **Acrodermatitis enteropathica** is a rare, inherited disorder characterized by a triad of **dermatitis**, **diarrhea**, and **alopecia**, primarily due to impaired zinc absorption. - **Zinc supplementation** is the cornerstone of treatment and typically leads to rapid resolution of symptoms. *Copper* - Copper deficiency can lead to **anemia**, **neutropenia**, and **neurological symptoms** like ataxia and peripheral neuropathy. - It does not cause the characteristic skin lesions of acrodermatitis enteropathica. *Vitamin A* - Vitamin A deficiency is associated with **xerophthalmia** (dry eyes), **night blindness**, and impaired immune function. - It does not present with acrodermatitis enteropathica. *Iron* - Iron deficiency causes **microcytic hypochromic anemia**, fatigue, and pica. - It does not manifest as the specific dermatological and gastrointestinal symptoms seen in acrodermatitis enteropathica.

Question 297: "Keratotic sandal" is seen in which of the following?

A. Tinea versicolor
B. Sezary syndrome
C. Reiter's disease
D. Pityriasis rubra pilaris (Correct Answer)

Explanation: ***Pityriasis rubra pilaris*** - "**Keratotic sandals**" refer to the characteristic **palmoplantar keratoderma** seen in pityriasis rubra pilaris, which gives the soles of the feet a thickened, yellowish appearance. - This condition also typically presents with **follicular papules**, **confluent erythematous plaques**, and often spared areas known as "islands of normal skin." *Tinea versicolor* - This is a **superficial fungal infection** characterized by **hypopigmented or hyperpigmented patches** with fine scaling, most commonly on the trunk and upper extremities. - It does not involve significant palmoplantar keratoderma or the formation of "keratotic sandals." *Sezary syndrome* - Sezary syndrome is an aggressive form of **cutaneous T-cell lymphoma** characterized by **erythroderma**, **lymphadenopathy**, and the presence of **Sezary cells** in the blood. - While skin involvement is extensive, the specific presentation of "keratotic sandals" is not a typical feature of Sezary syndrome. *Reiter's disease* - Reiter's disease, now known as **reactive arthritis**, is a seronegative spondyloarthropathy characterized by arthritis, urethritis, and conjunctivitis. - Skin manifestations can include **keratoderma blennorrhagicum**, which are papules and vesicles that become hyperkeratotic plaques, primarily on the palms and soles, but the term "keratotic sandals" is specifically associated with pityriasis rubra pilaris.

Question 298: Erythematous ringworm like lesions parallel to the ribs, with hanging curtain sign and Christmas tree pattern is suggestive of:

A. Pityriasis rubra pilaris
B. Psoriasis
C. Pityriasis Rosea (Correct Answer)
D. Lichen planus

Explanation: ***Pityriasis Rosea*** - **Pityriasis rosea** classically presents with an initial **herald patch**, followed by smaller, erythematous, oval-shaped lesions that align along the **skin cleavage lines** (Langer's lines), creating a **"Christmas tree" pattern** on the back. - The **"hanging curtain sign"** refers to the way the scales may detach at the periphery, resembling a hanging curtain, often seen with the characteristic ringworm-like lesions. *Pityriasis rubra pilaris* - This condition is characterized by **follicular papules** and **confluent erythematous plaques** with prominent **keratotic plugs**, often forming areas of orange-red scaling. - It typically exhibits an **island of sparing** where small patches of healthy skin are untouched, which is not described by the patient's symptoms. *Psoriasis* - **Psoriasis** presents as well-demarcated, **erythematous plaques** covered with thick, silvery scales, often on extensor surfaces like elbows and knees. - It does not specifically show a "Christmas tree" pattern or a "hanging curtain sign"; instead, it's known for the **Auspitz sign** (bleeding upon scale removal). *Lichen planus* - **Lichen planus** is characterized by **pruritic, purple, polygonal, planar papules and plaques** (the "6 P's"), often with fine white lines called **Wickham's striae**. - It commonly affects the flexor surfaces of wrists, forearms, and ankles, and can involve the oral mucosa, but does not present with ringworm-like lesions in a "Christmas tree" pattern.

Question 299: The wavelength of a Wood lamp is:

A. 280-320
B. 450-500
C. 400-450
D. 360-385 (Correct Answer)

Explanation: ***360-385*** - This wavelength range (measured in nanometers) corresponds to **long-wave ultraviolet A (UVA) light**, which is emitted by a Wood lamp. - This specific UVA spectrum is used to cause **fluorescence** in certain dermatological conditions or metabolites, making them visible. *280-320* - This range corresponds to **UVB light**, which is known for causing sunburn and is used in phototherapy for conditions like psoriasis, but not for Wood lamp examination. - Exposure to this wavelength is primarily responsible for **DNA damage** and skin carcinogenesis. *450-500* - These wavelengths fall within the **visible blue light** spectrum. - While various light sources can emit light in this range, it does not correspond to the specific **UV** output of a Wood lamp. *400-450* - This range is at the boundary of **visible violet light** and UVA. - Although it includes some UVA, the primary and most effective range for Wood lamp examinations is slightly lower, specifically the **360-385 nm** range.

Question 300: Which of the following is not a component of sebum?

A. Wax
B. Glycerides
C. Propylene (Correct Answer)
D. Cholesterol

Explanation: ***Propylene*** - **Propylene** (or polypropylene) is a synthetic polymer used in plastics and fibers, not a naturally occurring component of human sebum. - Sebum is a complex mixture of lipids produced by the sebaceous glands to lubricate the skin and hair. *Wax* - **Waxes** (specifically wax esters) are a significant component of sebum, contributing to its protective and hydrophobic properties. - These esters are formed from fatty acids and long-chain alcohols. *Glycerides* - **Glycerides**, particularly triglycerides (esters of glycerol and fatty acids), are major components of sebum, making up a large percentage of its total lipid content. - They contribute to the skin's lipid barrier and emollient properties. *Cholesterol* - **Cholesterol** and its esters are also present in sebum, playing a role in maintaining the integrity and fluidity of the skin barrier. - It works alongside other lipids to prevent water loss and protect against external factors.

Practice by Chapter

Structure and Function of Skin

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Cutaneous Histopathology

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Dermatological Examination

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Skin Lesions: Morphology and Description

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Principles of Diagnosis in Dermatology

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Dermatological Procedures

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Wound Healing

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Cutaneous Immunology

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Genetics in Dermatology

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Cutaneous Manifestations of Systemic Diseases

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Geriatric Dermatology

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Pediatric Dermatology Basics

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