Principles of Diagnosis in Dermatology — 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?
A child comes with a circular 3cm x 3cm scaly patchy hair loss with itching in the lesions. The investigation of choice is
Identify the diagnosis based on the dermatology immunofluorescence (IF) image provided.
A 7-year-old boy presented with painful boggy swelling of scalp, multiple sinuses with purulent discharge, easily pluckable hairs and lymph nodes enlarged in occipital region. Which one of the following would be most helpful for diagnostic evaluation?
Dyskeratosis refers to which of the following?
Comment on the image shown:
A 24-year-old male presents with a lesion at the site shown in the image for 4 years. He says it has increased in thickness over the years. Diagnosis is:
A 45-year-old Ulcerative colitis patient presents with multiple painful lesions on both legs. What is the diagnosis?
The following is an important feature of psoriasis:
A 35-year-old obese woman presents with recurrent lesions in both axilla in summer season. Wood lamp examination is shown. The diagnosis is:
Principles of Diagnosis in Dermatology 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: A child comes with a circular 3cm x 3cm scaly patchy hair loss with itching in the lesions. The investigation of choice is
- A. Tzanck smear
- B. Gram stain
- C. KOH mount (Correct Answer)
- D. Split skin smear
Explanation: ***Correct: KOH mount (Potassium Hydroxide mount)*** - A **KOH mount** is the investigation of choice for suspected **dermatophyte infections** (tinea capitis), which commonly present as circular, scaly patches of hair loss with itching in children. - It involves dissolving keratinous material to visualize **fungal hyphae** and spores directly under a microscope. - This is a quick, cost-effective, and highly specific first-line diagnostic test. *Incorrect: Tzanck smear* - A **Tzanck smear** is primarily used to diagnose **viral infections** like herpes simplex or varicella-zoster by identifying multinucleated giant cells. - It is not effective for detecting fungal elements responsible for scaly hair loss. *Incorrect: Gram stain* - A **Gram stain** is a technique used to classify **bacteria** based on their cell wall properties. - It would not reveal fungal hyphae or spores relevant to the described condition. *Incorrect: Split skin smear* - A **split skin smear** (or slit-skin smear) is typically used in the diagnosis of **leprosy** to identify acid-fast bacilli. - This technique involves scraping the dermis and is not suitable for diagnosing superficial fungal infections.
Question 3: Identify the diagnosis based on the dermatology immunofluorescence (IF) image provided.
- A. Pemphigus vulgaris
- B. Pemphigus foliaceus
- C. Bullous pemphigoid
- D. Dermatitis herpetiformis (Correct Answer)
Explanation: ***Dermatitis herpetiformis*** - The immunofluorescence image shows **granular IgA deposits** at the **dermal papillae region**, which is characteristic of dermatitis herpetiformis. - This condition is strongly associated with **celiac disease** and presents with intensely pruritic papules and vesicles. *Pemphigus vulgaris* - Immunofluorescence in pemphigus vulgaris typically shows a **fishnet pattern** of IgG deposits throughout the **epidermis**, reflecting antibodies against desmoglein 3 and 1. - This pattern is an intercellular deposition, not granular at the dermal papillae. *Pemphigus foliaceus* - Similar to pemphigus vulgaris, pemphigus foliaceus also exhibits **intercellular IgG deposits** in the epidermis, but it is usually more superficial, targeting desmoglein 1. - The image does not show this intercellular epidermal staining. *Bullous pemphigoid* - Bullous pemphigoid is characterized by **linear IgG and C3 deposits along the dermal-epidermal junction** (basement membrane zone). - The image distinctly shows granular IgA, not linear IgG/C3, and specifically in the dermal papillae.
Question 4: A 7-year-old boy presented with painful boggy swelling of scalp, multiple sinuses with purulent discharge, easily pluckable hairs and lymph nodes enlarged in occipital region. Which one of the following would be most helpful for diagnostic evaluation?
- A. Bacterial culture
- B. Biopsy
- C. KOH mount (Correct Answer)
- D. Patch test
Explanation: ***KOH mount*** - The symptoms described (painful boggy swelling of the scalp, multiple sinuses with purulent discharge, easily pluckable hairs, and occipital lymph nodes) are highly characteristic of **kerion celsi**, a severe inflammatory form of **tinea capitis**. - A **KOH mount** is the most direct and rapid method to confirm a fungal infection by visualizing fungal elements (hyphae and spores) from removed hairs or scalp scrapings. - It is the **first-line diagnostic test** for tinea capitis, providing results within minutes and having high specificity when positive. *Bacterial culture* - While there is purulent discharge, the primary pathology in kerion is fungal, not bacterial. Bacterial culture would likely show **secondary infection** rather than the underlying cause. - Antibiotics alone would not resolve the fungal infection, making a bacterial culture less helpful for the primary diagnosis. *Biopsy* - A biopsy would be more invasive and reveal an inflammatory reaction, but it is **not the first-line diagnostic test** for suspected tinea capitis. - While it can demonstrate fungal elements, a **KOH mount** is much quicker, less invasive, and equally effective for initial diagnosis. *Patch test* - A patch test is used to identify **allergic contact dermatitis** by applying specific allergens to the skin. - It is completely irrelevant for diagnosing a fungal infection like kerion celsi, which is an infection, not an allergic reaction.
Question 5: Dyskeratosis refers to which of the following?
- A. Abnormal, premature keratinization within cells below the stratum granulosum. (Correct Answer)
- B. Discontinuity of the skin showing incomplete loss of epidermis.
- C. Keratinization with retained nuclei in the stratum corneum.
- D. Thickening of stratum corneum, often associated with a qualitative abnormality of keratin.
Explanation: ***Abnormal, premature keratinization within cells below the stratum granulosum.*** - **Dyskeratosis** is a histological term for **premature keratinization** of individual keratinocytes. - This typically occurs in cells that are *below* the **stratum granulosum**, often in the stratum spinosum, indicating abnormal differentiation. *Discontinuity of the skin showing incomplete loss of epidermis.* - This description refers to an **erosion** or **ulceration**, depending on the depth of the epidermal loss. - It does not specifically describe abnormal cellular keratinization. *Keratinization with retained nuclei in the stratum corneum.* - This is the definition of **parakeratosis**, which is a normal finding in mucous membranes but an abnormal finding in skin, often associated with disorders like **psoriasis**. - It indicates incomplete maturation of keratinocytes as they reach the stratum corneum. *Thickening of stratum corneum, often associated with a qualitative abnormality of keratin.* - This describes **hyperkeratosis**, which is an increase in the thickness of the **stratum corneum**. - While it can involve abnormal keratin, it refers to increased thickness, not premature individual cell keratinization.
Question 6: Comment on the image shown:
- A. Corn
- B. Callosity (Correct Answer)
- C. Warts
- D. Cutaneous horn
Explanation: ***Callosity*** - The image displays several **thickened, hyperkeratotic patches** on the palm, characteristic of callosities. - Callosities are caused by repeated friction and pressure, leading to **diffuse epidermal thickening** without a central core. *Corn* - A **corn** is a small, well-demarcated lesion with a **central core** that causes localized pain, unlike the diffuse thickening seen here. - They typically occur over bony prominences and are less spread out than the lesions in the image. *Warts* - **Warts** are caused by the **human papillomavirus (HPV)** and present as rough, elevated lesions with characteristic **black puncta** (thrombosed capillaries) upon paring, which are not visible in the image. - They often have a **papillomatous** or verrucous surface, different from the relatively smooth, thickened appearance here. *Cutaneous horn* - A **cutaneous horn** is a conical projection of **hyperkeratotic material** resembling an animal horn, typically developing on sun-exposed areas. - It is usually a solitary lesion and has a different morphology than the multiple, flat, thickened lesions shown.
Question 7: A 24-year-old male presents with a lesion at the site shown in the image for 4 years. He says it has increased in thickness over the years. Diagnosis is:
- A. Spitz nevus
- B. Hyper-melanosis of Ito
- C. Becker's nevus (Correct Answer)
- D. Congenital melanocytic nevus
Explanation: ***Becker's nevus*** - This lesion typically presents as a **unilateral, hyperpigmented patch** that often appears during childhood or adolescence, increasing in size and thickness with associated **hypertrichosis** (increased hair growth). The image shows a large, irregularly shaped, hyperpigmented area on the torso of a young male, consistent with this description. - The history of increasing thickness over four years further supports **Becker's nevus**, as it is known to progress in thickness and texture, often becoming more indurated and sometimes verrucous. *Spitz nevus* - Spitz nevus is a benign melanocytic nevus typically presenting as a **pink or red, dome-shaped papule or nodule**, commonly on the face or limbs. - It rapidly grows but does not typically present as a large, hyperpigmented patch with associated hypertrichosis like the lesion shown. *Hyper-melanosis of Ito* - Hypermelanosis of Ito (also known as incontinentia pigmenti achromians) is characterized by **streaky or whorled hypopigmented (lighter) skin lesions**, often present at birth or in early infancy. - The image clearly shows a **hyperpigmented (darker) lesion**, which directly contradicts the characteristic hypopigmentation of hypermelanosis of Ito. *Congenital melanocytic nevus* - Congenital melanocytic nevi are typically present **at birth** or become apparent shortly thereafter. While they can be large and hyperpigmented, they usually do not have the prominent feature of increasing thickness and hypertrichosis developing many years later in adolescence or early adulthood in the same way as Becker's nevus. - The description of a lesion appearing during adolescence and increasing in thickness and hairiness for four years makes Becker's nevus a more specific diagnosis than a general congenital melanocytic nevus.
Question 8: A 45-year-old Ulcerative colitis patient presents with multiple painful lesions on both legs. What is the diagnosis?
- A. Pyoderma gangrenosum (Correct Answer)
- B. Febrile neutropenic dermatosis
- C. Necrotizing fasciitis
- D. Granulomatosis with polyangiitis
Explanation: ***Pyoderma gangrenosum*** - This patient has **ulcerative colitis**, which is strongly associated with **pyoderma gangrenosum**, a neutrophilic dermatosis. - The image shows characteristic **painful, rapidly expanding ulcers** with violaceous, undermined borders, typical of pyoderma gangrenosum. *Febrile neutropenic dermatosis* - This condition (also known as **Sweet syndrome**) occurs in patients with **neutropenia** and **fever**, presenting with painful erythematous plaques or nodules. - While systemic illness like ulcerative colitis can predispose to skin conditions, the specific presentation and lack of mentioned neutropenia make this less likely. *Necrotizing fasciitis* - **Necrotizing fasciitis** is a rapidly progressive, life-threatening infection of the deep fascia and subcutaneous tissue, typically presenting with severe pain, erythema, swelling, and crepitus. - The lesions in the image appear to be chronic ulcers with specific borders rather than acute, rapidly spreading infection of necrotizing fasciitis. *Granulomatosis with polyangiitis* - Also known as **Granulomatosis with polyangiitis (GPA)**, formerly **Wegener's granulomatosis**, this is an autoimmune vasculitis primarily affecting the respiratory tract and kidneys, and can cause skin lesions such as palpable purpura, nodules, or ulcers. - While skin lesions can occur, the characteristic features of **pyoderma gangrenosum** and its strong association with inflammatory bowel disease make it a more probable diagnosis in this context.
Question 9: The following is an important feature of psoriasis:
- A. Erythematous macules
- B. Crusting
- C. Silvery Scaling (Correct Answer)
- D. Coarse bleeding
Explanation: ***Silvery Scaling*** - **Silvery scaling** is a hallmark clinical feature of **psoriasis**, resulting from the rapid turnover of skin cells. - These scales often appear on **erythematous plaques** and can be easily scraped off, sometimes revealing pinpoint bleeding underneath (**Auspitz sign**). *Erythematous macules* - While psoriasis does involve **erythema** (redness), the primary lesions are typically **plaques**, not macules (flat, discolored spots). - Macules are seen in other dermatological conditions such as drug eruptions or early viral exanthems, but not as the definitive feature of psoriasis. *Crusting* - **Crusting** is a feature of conditions involving exudation and drying of serum, blood, or pus, such as **impetigo** or **eczema** with secondary infection. - It is not a characteristic primary lesion of psoriasis, although secondary infection of psoriatic plaques could theoretically lead to crusting. *Coarse bleeding* - **Coarse bleeding** is not a primary feature of psoriasis; however, when psoriatic scales are removed, pinpoint bleeding known as the **Auspitz sign** can occur. - This is distinct from frank, coarse bleeding and is a diagnostic clue rather than a characteristic lesion in itself.
Question 10: A 35-year-old obese woman presents with recurrent lesions in both axilla in summer season. Wood lamp examination is shown. The diagnosis is:
- A. Ecthyma
- B. Erythrasma (Correct Answer)
- C. Impetigo contagiosa
- D. Bullous impetigo
Explanation: ***Erythrasma*** - Erythrasma is a superficial bacterial infection caused by **Corynebacterium minutissimum**, which commonly presents as red-brown patches in intertriginous areas like the axilla, especially in obese individuals and warm, humid conditions (summer season). - The distinctive **coral-red fluorescence under Wood's lamp** is due to porphyrin production by the bacteria, which is a classic diagnostic feature of erythrasma, as shown in the image. *Ecthyma* - Ecthyma is a deeper form of impetigo characterized by **ulcerative lesions with a thick, adherent crust** that extend into the dermis. - It is typically caused by *Streptococcus pyogenes* and sometimes *Staphylococcus aureus*, and would not exhibit coral-red fluorescence under Wood's lamp. *Impetigo contagiosa* - Impetigo contagiosa (non-bullous impetigo) presents with **honey-colored crusted lesions**, usually on the face and extremities. - While also a bacterial skin infection, it is typically caused by *Staphylococcus aureus* or *Streptococcus pyogenes* and does not show coral-red fluorescence under Wood's lamp. *Bullous impetigo* - Bullous impetigo is characterized by **flaccid bullae** (blisters) that rupture to form thin, varnish-like crusts, primarily caused by *Staphylococcus aureus* producing exfoliative toxins. - Similar to other forms of impetigo, it does not produce the coral-red fluorescence under Wood's lamp.
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