Basic Dermatology — MCQs

Basic Dermatology Indian Medical PG Practice Questions and MCQs

Question 181: Which of the following statements is FALSE regarding Sweet's syndrome?

A. May be associated with high fever
B. Neutrophilia is not present (Correct Answer)
C. May be associated with hematological malignancy
D. Pseudovesication

Explanation: ***Neutrophilia is not present*** - **Neutrophilia** is actually a **hallmark feature** of Sweet's syndrome, making this statement false. - The condition is characterized by **dense neutrophilic infiltration** in the dermis and elevated **peripheral neutrophil count**. *May be associated with high fever* - **High fever** (>38°C) is a **major criterion** for diagnosing Sweet's syndrome. - Systemic symptoms including fever are present in approximately **80% of patients**. *May be associated with hematological malignancy* - **Acute myelogenous leukemia** is the most common associated malignancy in Sweet's syndrome. - Up to **20% of cases** are **malignancy-associated**, particularly with **hematological cancers**. *Pseudovesication* - **Pseudovesicles** are characteristic lesions that appear **vesicular** but lack true **intraepidermal fluid**. - This occurs due to **marked papillary dermal edema** causing separation at the **dermal-epidermal junction**.

Question 182: What is parakeratosis defined as?

A. Retained nuclei in stratum corneum cells (Correct Answer)
B. Elongation of rete ridges
C. Increased number of cells in stratum spinosum
D. Increased thickness of stratum corneum

Explanation: **Explanation:** **Parakeratosis** is a histopathological term defined as the **retention of nuclei in the cells of the stratum corneum** (the outermost layer of the epidermis). In normal skin, keratinocytes lose their nuclei as they migrate upward and mature into corneocytes. Parakeratosis signifies an accelerated or abnormal keratinization process where the turnover time of the epidermis is so rapid that the cells do not have sufficient time to lose their nuclei before reaching the surface. **Analysis of Options:** * **Option A (Correct):** This is the hallmark of parakeratosis. It is characteristically seen in diseases with high epidermal turnover, most notably **Psoriasis**. * **Option B (Incorrect):** Elongation of rete ridges is termed **Acanthosis** (specifically regular acanthosis when uniform). * **Option C (Incorrect):** An increase in the number of cells in the stratum spinosum (prickle cell layer) is also referred to as **Acanthosis**, leading to overall epidermal thickening. * **Option D (Incorrect):** Increased thickness of the stratum corneum is called **Hyperkeratosis**. While parakeratosis often coexists with hyperkeratosis, they are distinct processes. **NEET-PG High-Yield Pearls:** 1. **Psoriasis:** Shows "confluent parakeratosis" and a diminished or absent stratum granulosum. 2. **Munro’s Microabscess:** Collections of neutrophils within the parakeratotic stratum corneum (pathognomonic for Psoriasis). 3. **Granular Layer Relationship:** Generally, where there is parakeratosis, the underlying **stratum granulosum is thin or absent** (except in Granular Parakeratosis). 4. **Pityriasis Rosea:** Characterized by "mound-like" parakeratosis.

Question 183: Well-circumscribed, flat lesions that are inflamed or pigmented are known as which of the following?

A. Papule
B. Macule (Correct Answer)
C. Bullae
D. Pustule

Explanation: ### Explanation **Correct Answer: B. Macule** **1. Why Macule is Correct:** In dermatology, a **macule** is defined as a flat, circumscribed area of altered skin color that is **less than 1 cm** in diameter. Since it is flat, it is not palpable (you cannot feel a change in texture or height when closing your eyes). The change in color can be due to inflammation (erythema), hyperpigmentation (melanin), hypopigmentation, or vascular changes. If a flat lesion is larger than 1 cm, it is termed a **patch**. **2. Why Other Options are Incorrect:** * **A. Papule:** A papule is a solid, **elevated** (palpable) lesion less than 1 cm in diameter. The question specifies "flat" lesions, which excludes papules. * **C. Bullae:** These are circumscribed, **fluid-filled** elevations (blisters) greater than 1 cm in diameter. They are elevated and contain serous fluid, not just a change in color. * **D. Pustule:** A pustule is a small, elevated circumscribed cavity filled with **purulent exudate** (pus). It is palpable and typically has a yellow or white center. **3. Clinical Pearls for NEET-PG:** * **Size Threshold:** The "magic number" in primary skin lesions is **1 cm**. * Flat: Macule (<1 cm) vs. Patch (>1 cm). * Elevated (Solid): Papule (<1 cm) vs. Plaque (>1 cm). * Elevated (Fluid): Vesicle (<1 cm) vs. Bulla (>1 cm). * **High-Yield Example:** Vitiligo often starts as macules that coalesce into patches. Freckles (ephelides) are classic examples of pigmented macules. * **Nodule:** A solid, palpable lesion >1 cm with a significant dermal component (depth).

Question 184: An 18-year-old female presents with itchy erythema and swelling of her toes every winter season. What is the most likely diagnosis?

A. Raynaud's disease
B. Raynaud's phenomenon
C. Chilblains (Correct Answer)
D. Frostbite

Explanation: **Explanation:** **Correct Answer: C. Chilblains (Pernio)** Chilblains is a localized inflammatory lesion of the skin caused by an abnormal vascular response to **non-freezing cold and humidity**. It typically affects young females and presents as itchy, painful, erythematous, or cyanotic swellings on the acral areas (toes, fingers, ears). The hallmark is its **seasonal recurrence** during winter and spontaneous resolution in warmer weather. The underlying mechanism involves cold-induced vasoconstriction of small cutaneous arterioles followed by sudden vasodilation, leading to edema and inflammation. **Why other options are incorrect:** * **Raynaud’s Disease/Phenomenon (A & B):** These present with a classic **triphasic color change** (Pallor/White → Cyanosis/Blue → Rubor/Red) triggered by cold. While they affect the extremities, they are characterized by paroxysmal vasospasm rather than persistent inflammatory swelling and itching. * **Frostbite (D):** This involves actual **freezing of tissues** (ice crystal formation) due to exposure to temperatures below freezing point ($<0^\circ\text{C}$). It results in tissue necrosis and is much more severe than the inflammatory response seen in chilblains. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Presentation:** "Pernio" is the medical term; look for the "itchy-painful" combination in winter. * **Treatment:** The drug of choice for severe or refractory cases is **Nifedipine** (a Calcium Channel Blocker), which promotes vasodilation. * **Secondary Chilblains:** If lesions occur outside of winter or are persistent, suspect **Lupus Erythematosus** (Chilblain Lupus). * **Prevention:** Keeping extremities warm and dry is the primary management strategy.

Question 185: What is true about Erythema elevatum diutinum?

A. Chronic cutaneous fungal infection
B. Most common site of involvement is the trunk
C. A cutaneous marker of glucagonoma
D. Dapsone is the drug of choice (Correct Answer)

Explanation: **Erythema Elevatum Diutinum (EED)** is a rare, chronic form of localized cutaneous small-vessel vasculitis (leukocytoclastic vasculitis). ### **Explanation of Options** * **Dapsone is the drug of choice (Correct):** Dapsone is highly effective and considered the first-line treatment for EED. It works by inhibiting neutrophil chemotaxis and the deposition of antibodies, leading to rapid resolution of the lesions. * **Chronic cutaneous fungal infection (Incorrect):** EED is a **neutrophilic dermatosis** and a type of vasculitis, not an infection. It is often associated with underlying systemic conditions like IgA monoclonal gammopathy, HIV, or autoimmune diseases. * **Most common site is the trunk (Incorrect):** The hallmark of EED is its **symmetrical distribution over extensor surfaces** of the joints (knees, elbows, small joints of hands and feet). The trunk is rarely involved. * **Cutaneous marker of glucagonoma (Incorrect):** The cutaneous marker for a glucagonoma is **Necrolytic Migratory Erythema (NME)**. EED is instead a marker for plasma cell dyscrasias (specifically IgA paraproteinemia). ### **Clinical Pearls for NEET-PG** * **Morphology:** Presents as red-violet to yellowish-brown papules, plaques, or nodules that eventually become fibrotic. * **Histopathology:** Early lesions show **Leukocytoclastic Vasculitis (LCV)** with a "starry sky" appearance of nuclear dust. Older lesions show characteristic **concentric perivascular fibrosis** (onion-skinning). * **Key Association:** Always screen patients with EED for **IgA Monoclonal Gammopathy**, as this is the most common systemic association. * **Differential Diagnosis:** Sweet Syndrome (also a neutrophilic dermatosis but presents with fever and painful plaques) and Granuloma Faciale.

Question 186: What condition is characterized by "target lesions"?

A. Dermatitis herpetiformis
B. Sulpha drug reaction
C. Lichen planus
D. Erythema multiforme (Correct Answer)

Explanation: **Explanation:** **Erythema Multiforme (EM)** is the classic condition characterized by **target (iris) lesions**. These are pathognomonic, three-zoned concentric rings: a central dusky/blistering area, a middle pale edematous ring, and an outer erythematous halo. This hypersensitivity reaction is most commonly triggered by **Herpes Simplex Virus (HSV)**, though Mycoplasma pneumoniae and certain drugs can also be causative agents. **Analysis of Incorrect Options:** * **Dermatitis Herpetiformis:** Characterized by intensely pruritic, grouped (herpetiform) vesicles on an erythematous base, typically on extensor surfaces. It is strongly associated with **Celiac disease** and shows IgA deposits on direct immunofluorescence. * **Sulpha Drug Reaction:** While sulpha drugs can cause EM or Stevens-Johnson Syndrome (SJS), they are more classically associated with **Fixed Drug Eruptions (FDE)**, which present as recurrent, well-demarcated dusky red plaques at the same anatomical site. * **Lichen Planus:** Characterized by the "6 Ps": Planar (flat-topped), Purple, Polygonal, Pruritic, Papules, and Plaques. It features **Wickham striae** (whitish reticular lines) rather than target lesions. **High-Yield Clinical Pearls for NEET-PG:** * **Minor vs. Major:** EM Minor involves skin only; EM Major involves skin and at least one mucosal surface (usually oral). * **Atypical Targets:** Two-zoned lesions (lacking the middle pale ring) are seen in SJS/TEN, whereas **classic three-zoned targets** are specific to EM. * **Histology:** Look for "satellite cell necrosis" (individual keratinocyte death) and subepidermal edema.

Question 187: Hyperkeratosis is defined as:

A. Thinning of the stratum corneum
B. Thickening of the stratum corneum (Correct Answer)
C. Thinning of the stratum basale
D. Thickening of the stratum basale

Explanation: **Explanation:** **Hyperkeratosis** is a histopathological term defined as the **thickening of the stratum corneum** (the outermost layer of the epidermis). This occurs due to an increased production of keratinocytes or a delay in desquamation. It is a hallmark feature of many dermatological conditions, such as psoriasis, chronic eczema, and calluses. * **Option B is correct:** The stratum corneum consists of dead, keratinized cells. When this layer expands beyond its normal thickness, it is termed hyperkeratosis. It can be further classified into *orthokeratotic* (normal nuclei loss) or *parakeratotic* (retention of nuclei). * **Option A is incorrect:** Thinning of the stratum corneum is not a standard pathological term but may occur in certain atrophic skin conditions. * **Options C & D are incorrect:** The stratum basale is the deepest layer of the epidermis. Thickening of the overall viable epidermis (excluding the stratum corneum) is known as **Acanthosis**, not hyperkeratosis. **High-Yield Clinical Pearls for NEET-PG:** 1. **Acanthosis:** Thickening of the stratum spinosum (prickly cell layer). 2. **Parakeratosis:** Retention of nuclei in the stratum corneum (seen in Psoriasis). 3. **Hypergranulosis:** Thickening of the stratum granulosum (seen in Lichen Planus). 4. **Spongiosis:** Intercellular edema within the epidermis (characteristic of Eczema/Dermatitis). 5. **Munro’s Microabscess:** Neutrophils in the stratum corneum, specifically seen in Psoriasis.

Question 188: What is the primary function of Langerhans cells?

A. Phagocytosis
B. Antigen presentation (Correct Answer)
C. Associated with autoimmune conditions
D. Associated with chronic infections

Explanation: **Explanation:** **Langerhans cells (LCs)** are specialized dendritic cells located primarily in the **Stratum Spinosum** of the epidermis. Their primary function is **Antigen Presentation**. As the skin’s "sentinels," they capture exogenous antigens via their dendrites, process them, and migrate to regional lymph nodes. There, they present these antigens to naive T-cells, initiating an adaptive immune response (specifically Type IV hypersensitivity). **Analysis of Options:** * **Option B (Correct):** LCs are professional antigen-presenting cells (APCs). They express MHC Class II molecules and contain characteristic **Birbeck granules** (tennis-racket shaped), which are involved in endocytosis. * **Option A:** While LCs can internalize particles, their primary physiological role is not systemic clearance (phagocytosis), which is the domain of macrophages/neutrophils. * **Options C & D:** While LCs are involved in the immune milieu of various diseases, they are not specifically defined by an association with autoimmune conditions or chronic infections in a diagnostic sense. **High-Yield Clinical Pearls for NEET-PG:** * **Origin:** Derived from the **Bone Marrow** (monocyte-macrophage lineage). * **Markers:** Positive for **CD1a, S100, and Langerin (CD207)**. * **Electron Microscopy:** Pathognomonic **Birbeck granules** (tennis-racket appearance). * **Clinical Correlation:** **Langerhans Cell Histiocytosis (LCH)** is a proliferative disorder where these cells infiltrate various organs. On imaging, it may present as "punched-out" lytic bone lesions.

Question 189: Which of the following conditions does not show an isomorphic type of Koebner phenomenon?

A. Molluscum contagiosum (Correct Answer)
B. Vitiligo
C. Psoriasis
D. None of the above

Explanation: ### Explanation The **Koebner phenomenon** (isomorphic response) refers to the development of skin lesions characteristic of a pre-existing dermatosis at the site of trauma or injury to previously healthy skin. #### Why Molluscum Contagiosum is the Correct Answer While **Molluscum contagiosum** (MC) often shows lesions appearing in a linear pattern due to scratching (autoinoculation), this is termed **Pseudo-Koebner phenomenon**. The distinction lies in the underlying mechanism: * **True Koebner:** An isomorphic response in non-infectious inflammatory or metabolic skin diseases. * **Pseudo-Koebner:** Occurs in infectious conditions (e.g., MC, Viral Warts) where trauma physically spreads the infectious agent (virus) to a new site. #### Analysis of Incorrect Options * **B. Vitiligo:** This is a classic example of the **True Koebner phenomenon**. Trauma to the skin can trigger the destruction of melanocytes, leading to new depigmented patches in a linear or traumatic distribution. * **C. Psoriasis:** This is the most common and prototypical condition associated with the Koebner phenomenon. Approximately 25% of psoriasis patients exhibit this response following triggers like surgery, scratches, or sunburns. #### NEET-PG High-Yield Pearls * **Common True Koebner conditions:** Psoriasis, Lichen Planus, Vitiligo, Pityriasis Rubra Pilaris (PRP). * **Pseudo-Koebner conditions:** Molluscum contagiosum, Verruca plana (Warts), Impetigo. * **Reverse Koebner:** Disappearance of a lesion following trauma (e.g., Psoriasis, Granuloma annulare). * **Wolf’s Isotopic Response:** Occurrence of a new skin disease at the exact site of a previously healed, unrelated skin disease (most commonly post-Herpes Zoster).

Question 190: What is the most likely diagnosis for yellow nodules over the palm?

A. Implantation dermoid
B. Sebaceous cysts
C. Corn (Correct Answer)
D. Melanoma

Explanation: **Explanation:** **Corns (Clavus)** are localized areas of hyperkeratosis that develop due to chronic pressure or friction over bony prominences. Clinically, they present as well-circumscribed, painful, **yellowish-translucent nodules** with a central hard core (radix). While more common on the toes, they frequently occur on the palms in individuals performing manual labor or repetitive mechanical tasks. The yellow color is characteristic of the dense, compacted keratin. **Why other options are incorrect:** * **Implantation Dermoid:** These are subcutaneous cysts resulting from traumatic implantation of epidermal elements. They typically present as skin-colored, firm, non-tender nodules, usually lacking the yellowish hyperkeratotic surface of a corn. * **Sebaceous Cysts:** These are rare on the palms because the palmar skin is **glabrous** (lacks hair follicles and sebaceous glands). They are characterized by a central punctum and cheesy discharge. * **Melanoma:** Acral lentiginous melanoma is the most common subtype on palms/soles, but it typically presents as an irregular, darkly pigmented (black/brown) macule or nodule, not a yellow hyperkeratotic lesion. **High-Yield Clinical Pearls for NEET-PG:** * **Corn vs. Wart:** To differentiate, pare the surface. A **corn** shows a central translucent core and preservation of skin lines, whereas a **viral wart (verruca)** shows pinpoint bleeding (thrombosed capillaries) and disruption of skin lines. * **Hard Corns** are usually found on the dorsal aspect of toes; **Soft Corns** occur in interdigital spaces due to maceration. * **Treatment:** Salicylic acid (keratolytic), paring, or surgical excision.

Practice by Chapter

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