Basic Dermatology Practice Questions

Q: Which of the following conditions is associated with acanthosis nigricans?

Type 2 Diabetes Mellitus. Acanthosis nigricans is characterized by velvety, hyperpigmented skin lesions, often in intertriginous areas, and is a common cutaneous marker for insulin resistance, which is central to Type 2 Diabetes Mellitus [1]. The elevated insulin levels stimulate epidermal keratinocytes and dermal fibroblast proliferation, leading to the characteristic skin changes. While malignant acanthosis nigricans is associated with internal malignancies, particularly adenocarcinomas of the gastrointestinal tract (like gastric), it is a less common cause than insulin resistance. This form is usually more extensive and rapidly progressing than the benign variant. Obesity is strongly associated with insulin resistance, making it an indirect cause of acanthosis nigricans. However, acanthosis nigricans is a direct indicator of insulin resistance, which can occur with or without significant obesity. While all listed conditions can be associated with acanthosis nigricans, Type 2 Diabetes Mellitus is the most direct and common condition explicitly linked to the underlying pathophysiology of insulin resistance [1]. Gastric adenocarcinoma causes a malignant form, and obesity is a risk factor for insulin resistance, but T2DM directly reflects the metabolic state responsible for the skin changes.

Q: All of the following regarding lichen planus are true except which of the following?

Does not involve mucous membrane. ***Does not involve mucous membrane*** - **Lichen planus** frequently involves mucous membranes, particularly the **oral mucosa**, where it can present as white reticular striae (Wickham's striae) or erosive lesions. - Mucous membrane involvement is a key diagnostic feature and can be painful, affecting eating and drinking. *Associated with Hepatitis 'C'* - There is a well-established association between **lichen planus** and **Hepatitis C virus** (HCV) infection, particularly in cases of oral lichen planus. - HCV infection can trigger or exacerbate immune-mediated conditions like lichen planus. *Topical steroids are the mainstay of therapy* - **Topical corticosteroids** are indeed the **first-line treatment** for many forms of lichen planus, especially localized cutaneous or oral lesions, to reduce inflammation and symptoms. - For more severe or widespread cases, systemic corticosteroids or other immunomodulators may be used. *Spontaneous remission occurs after 6 months to 2 years* - **Lichen planus** often undergoes **spontaneous remission**, typically within **6 months to 2 years** for cutaneous forms. - However, oral lichen planus tends to be more chronic and persistent.

Q: Which "P" describes the characteristic shape of lichen planus lesions?

Polygonal. ***Polygonal*** - Lichen planus lesions are classically described as having a **polygonal (angular) shape**, one of the "6 Ps" of lichen planus. - The papules have **distinct, angular borders** that create a geometric, many-sided appearance. - This is a key morphological feature used to identify lichen planus clinically. *Polyhedral* - **Polyhedral** refers to a three-dimensional solid figure with many faces (like a crystal or polyhedron). - This term does not describe the two-dimensional shape of skin lesions. - Not part of the classic "6 Ps" mnemonic. *Plane* - While lichen planus lesions are **planar (flat-topped)**, which IS one of the "6 Ps," this describes the **surface topography**, not the **shape** of the lesions. - "Plane/planar" refers to the flat surface when viewed from the side, whereas "polygonal" describes the angular outline when viewed from above. *Pruritus* - **Pruritic (itchy)** is indeed one of the "6 Ps" of lichen planus and a very common clinical feature. - However, pruritus describes a **symptom**, not the **shape** of the lesions. - The question specifically asks about shape characteristics.

Q: Which of the following statements about Pityriasis rosea is true?

It is a self-limiting condition.. ***It is a self-limiting condition.*** - **Pityriasis rosea** is characterized by a distinctive rash that typically resolves on its own within **6-8 weeks** without specific treatment. - Most patients experience complete resolution, and **recurrences are uncommon**. - Often preceded by a **herald patch** followed by smaller oval lesions in a **"Christmas tree" distribution** on the trunk. *It can lead to life-threatening infections.* - While the exact etiology is unknown, **Pityriasis rosea** is generally considered **benign** and does not typically lead to systemic complications or life-threatening infections. - The rash itself is a localized skin condition that does not compromise the immune system or predispose to severe secondary infections. *It is caused by dermatophytes.* - **Dermatophytes** are fungi that cause superficial fungal infections such as ringworm (**tinea** infections). - **Pityriasis rosea** is thought to be triggered by certain **viral infections**, particularly **human herpesvirus 6 (HHV-6)** and **HHV-7**, not fungal organisms. - This helps differentiate it from fungal conditions like tinea corporis. *It is a chronic relapsing condition.* - **Pityriasis rosea** is generally an **acute, self-limiting eruption** that resolves spontaneously, making it distinct from chronic, relapsing conditions such as **psoriasis** or **eczema**. - A single episode usually confers long-lasting immunity, and **recurrences are rare** (occurring in <2% of cases).

Q: Darier's disease is associated with:

ATP2A2 gene mutation and acantholytic dyskeratosis. ***ATP2A2 gene mutation and acantholytic dyskeratosis*** - This is the **correct association for Darier's disease** (keratosis follicularis), an autosomal dominant genodermatosis - Caused by mutation in the **ATP2A2 gene** on chromosome 12q23-24.1, which encodes **SERCA2** (calcium ATPase pump in endoplasmic reticulum) - Defective calcium signaling leads to impaired keratinocyte adhesion and differentiation - Results in **acantholytic dyskeratosis** - the hallmark histopathological finding showing abnormal keratinization and loss of cohesion between epidermal cells - **Clinical features:** greasy keratotic papules in seborrheic distribution, palmoplantar pits, nail abnormalities with V-shaped nicking *Autoimmune destruction of melanocytes* - This describes **vitiligo**, not Darier's disease - Vitiligo is characterized by autoimmune destruction of melanocytes leading to depigmented patches - Completely unrelated to the genetic and structural defects seen in Darier's disease *Vitamin A deficiency and night blindness* - **Vitamin A deficiency** causes ocular manifestations including **night blindness (nyctalopia)** and xerophthalmia - Also causes skin changes like **follicular hyperkeratosis (phrynoderma)** - Not associated with Darier's disease, which is a genetic disorder *Human papillomavirus infection and wart formation* - **HPV infection** causes **warts (verrucae)** - benign epithelial proliferations - Results from viral infection of keratinocytes, not genetic calcium pump dysfunction - Unrelated to Darier's disease pathophysiology

Q: What is the wavelength of ultraviolet (UV) rays used in a Woods lamp for dermatological examination?

360 nm. ***360 nm*** - A **Woods lamp** uses **long-wave ultraviolet A (UV-A)** radiation, which typically ranges from **320 to 400 nm**. - **360 nm** falls within this range and is the approximate peak wavelength used to induce fluorescence in various dermatological conditions. *460 nm* - This wavelength falls in the **visible blue light spectrum**, not the ultraviolet spectrum. - While visible light can be used for examination, it does not induce the characteristic fluorescence observed with a Woods lamp. *660 nm* - This wavelength is in the **visible red light spectrum**. - Red light is not used in a Woods lamp for dermatological diagnostic purposes, as it does not produce the necessary fluorescence. *760 nm* - This wavelength falls into the **near-infrared spectrum**, which is beyond visible light and the UV range. - Infrared radiation has different applications in medicine but is not used in a Woods lamp.

Q: What is the optimal wavelength of light emitted by a Wood's lamp for dermatological examinations?

365 nm. **365 nm** - A Wood's lamp primarily emits **long-wave UVA light** in the 320 to 400 nm range, with an optimal peak around **365 nm**. - This specific wavelength is ideal for inducing **fluorescence** in various dermatological conditions, making them visible. *400 nm* - While within the UVA range, **400 nm** is at the higher end and may not provide the optimal fluorescence yield for all diagnostic purposes compared to 365 nm. - Light at 400 nm is closer to the visible light spectrum and might offer less distinction for subtle fluorescence. *320 nm* - **320 nm** is at the lower end of the UVA spectrum, bordering on UVB. - While still capable of inducing some fluorescence, it is generally less effective than 365 nm for the conditions typically examined with a Wood's lamp. *200 nm* - **200 nm** falls into the **UVC range** (100-280 nm), which is harmful and not used for diagnostic purposes in a Wood's lamp. - This wavelength is absorbed by the atmosphere and epidermis and can cause significant **DNA damage**, making it unsafe for routine dermatological examination.

Q: Palpable purpura could occur in the following conditions, except:

Thrombocytopenia. ***Correct: Thrombocytopenia*** - In **pure thrombocytopenia**, bleeding manifests as **petechiae** (pinpoint, non-palpable red spots) and **ecchymoses** (bruises), which are typically **non-palpable** and result from extravasated blood **without inflammation**. - **Palpable purpura** requires inflammation of blood vessels (vasculitis), which is absent in simple platelet deficiency. *Incorrect: Small-vessel vasculitis* - **Palpable purpura** is the **classic hallmark** of small-vessel vasculitis (leukocytoclastic vasculitis). - Results from **immune complex deposition** in vessel walls, leading to inflammatory cell infiltration and palpable lesions. - Conditions like **Henoch-Schönlein purpura** and **hypersensitivity vasculitis** characteristically present with palpable purpura. *Incorrect: Disseminated gonococcal infection* - Can cause **septic vasculitis** with palpable purpuric lesions. - Presents with **papulopustular or hemorrhagic lesions** that may progress from macules/petechiae to palpable purpura. - Lesions are typically few in number and occur on distal extremities. *Incorrect: Acute meningococcemia* - Presents with rapidly progressive rash: **macules → papules → petechiae → purpura**. - Purpuric lesions become **palpable** due to thrombosis and vessel inflammation. - Severe purpura can coalesce into large ecchymoses with necrotic centers.

Q: A young boy presented with a lesion over his right buttock, which had peripheral scaling and central scarring. What is the most appropriate investigation to confirm the diagnosis?

Biopsy. ***Biopsy*** - A lesion with **peripheral scaling** and **central scarring** strongly suggests conditions such as **discoid lupus erythematosus** or potentially **tinea profunda** (Majocchi's granuloma), making a biopsy the most definitive diagnostic tool. - A **biopsy** allows for histopathological examination, which can identify specific cellular and architectural changes characteristic of these dermatological conditions, differentiating between inflammatory, infectious, and autoimmune causes. *Tzank Smear* - A **Tzank smear** is primarily used to detect multinucleated giant cells seen in **herpes simplex** or **varicella zoster virus infections**. - This technique is not suitable for diagnosing lesions characterized by scaling and scarring, which point to chronic inflammatory or granulomatous processes. *KOH preparation* - A **KOH preparation** (potassium hydroxide) is used to identify **fungal elements** such as hyphae and spores in skin scrapings. - While it could rule out a superficial fungal infection, the presence of **central scarring** suggests a more chronic and deeper process not typically diagnosed by KOH alone. *Sabouraud's agar* - **Sabouraud's agar** is a culture medium specifically used for growing **fungi** from skin scrapings or biopsies. - While it can help confirm a fungal infection, a **biopsy** remains crucial for histological evaluation, especially when a lesion presents with scarring and atypical morphology.

Question 1

Which of the following conditions is associated with acanthosis nigricans?

Accepted Answer

Type 2 Diabetes Mellitus

Answer

Obesity

Answer

Gastric adenocarcinoma

Answer

All of the options

Question 2

Dyskeratosis refers to which of the following?

Accepted Answer

Abnormal, premature keratinization within cells below the stratum granulosum.

Answer

Discontinuity of the skin showing incomplete loss of epidermis.

Answer

Keratinization with retained nuclei in the stratum corneum.

Answer

Thickening of stratum corneum, often associated with a qualitative abnormality of keratin.

Question 3

All of the following regarding lichen planus are true except which of the following?

Accepted Answer

Does not involve mucous membrane

Answer

Associated with Hepatitis 'C'

Answer

Topical steroids are the mainstay of therapy

Answer

Spontaneous remission occurs after 6 months to 2 years

Question 4

Which "P" describes the characteristic shape of lichen planus lesions?

Accepted Answer

Polygonal

Answer

Polyhedral

Answer

Plane

Answer

Pruritus

Question 5

Which of the following statements about Pityriasis rosea is true?

Accepted Answer

It is a self-limiting condition.

Answer

It can lead to life-threatening infections.

Answer

It is caused by dermatophytes.

Answer

It is a chronic relapsing condition.

Question 6

Darier's disease is associated with:

Accepted Answer

ATP2A2 gene mutation and acantholytic dyskeratosis

Answer

Vitamin A deficiency and night blindness

Answer

Human papillomavirus infection and wart formation

Answer

Autoimmune destruction of melanocytes

Question 7

What is the wavelength of ultraviolet (UV) rays used in a Woods lamp for dermatological examination?

Accepted Answer

360 nm

Answer

460 nm

Answer

660 nm

Answer

760 nm

Question 8

What is the optimal wavelength of light emitted by a Wood's lamp for dermatological examinations?

Accepted Answer

365 nm

Answer

400 nm

Answer

320 nm

Answer

200 nm

Question 9

Palpable purpura could occur in the following conditions, except:

Accepted Answer

Thrombocytopenia

Answer

Disseminated gonococcal infection

Answer

Acute meningococcemia

Answer

Small-vessel vasculitis

Question 10

A young boy presented with a lesion over his right buttock, which had peripheral scaling and central scarring. What is the most appropriate investigation to confirm the diagnosis?

Accepted Answer

Biopsy

Answer

Tzank Smear

Answer

KOH preparation

Answer

Sabouraud's agar

Basic Dermatology — MCQs

Basic Dermatology — MCQs

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