Basic Dermatology Practice Questions

Q: A 45-year-old man presents with multiple firm, yellowish nodules on his extensor surfaces. What is the most likely diagnosis?

Xanthomas. ***Xanthomas*** - **Xanthomas** are deposits of **cholesterol** and **lipids** in the skin, often appearing as firm, yellowish nodules. - They commonly occur on **extensor surfaces** such as elbows, knees, and Achilles tendons, and are associated with **hyperlipidemia**. *Lipomas* - **Lipomas** are benign tumors composed of **fat cells**, which are typically soft, movable, and painless. - While they can occur on extensor surfaces, they are generally **not yellowish** and do not indicate a systemic lipid disorder. *Seborrheic keratosis* - **Seborrheic keratoses** are common, benign skin growths that tend to be **waxy, 'stuck-on'** in appearance, and range in color from light tan to black. - They do not typically present as firm, yellowish nodules on extensor surfaces and are not associated with lipid abnormalities. *Erythema nodosum* - **Erythema nodosum** presents as tender, red, or violaceous nodules, primarily on the **shins**. - These lesions are painful and resolve with bruising-like discoloration, which is distinct from the firm, yellowish, non-tender nodules described.

Q: Which skin condition is characterized by a 'herald patch'?

Pityriasis rosea. ***Pityriasis rosea*** - A **herald patch** is the initial, solitary, larger lesion that precedes the generalized rash of pityriasis rosea. - The subsequent rash typically appears in a **Christmas tree pattern** on the trunk. *Psoriasis* - Characterized by well-demarcated, **erythematous plaques** with silvery scales, often on extensor surfaces. - It does not present with a "herald patch"; its onset is typically gradual with the development of multiple lesions. *Lichen planus* - Presents with **pruritic, polygonal, planar, purple papules and plaques** (the 6 P's), often affecting the skin, hair, nails, and mucous membranes. - Does not feature a herald patch as part of its typical presentation. *Eczema* - A broad term for several skin conditions characterized by **itchy, inflamed skin**, often with redness, dryness, and sometimes blistering or weeping. - It does not involve a herald patch; its lesions can be localized or widespread, varying by type (e.g., atopic, contact).

Q: A 30-year-old male presents with recurrent episodes of erythematous target-like lesions, primarily on the hands and forearms, often following herpes simplex outbreaks. What is the most likely diagnosis?

Erythema multiforme. ***Erythema multiforme*** - Erythema multiforme is characterized by **target-like lesions** with concentric rings of color, typically found on the **hands and forearms**. - It is frequently triggered by **herpes simplex virus (HSV) infection**, which aligns with the recurrent episodes following herpes outbreaks. *Urticaria* - Urticaria (hives) presents as **itchy, transient wheals** that are usually migratory and do not have the classic targetoid appearance. - While it can be recurrent, it is typically an allergic reaction and less commonly directly linked to HSV infections. *Fixed drug eruption* - This condition involves **solitary or a few well-demarcated, often pigmented, erythematous plaques** that recur at the same site(s) with re-exposure to a specific drug. - It does not present with target lesions or a clear association with HSV outbreaks. *Psoriasis* - Psoriasis typically presents with **well-demarcated, erythematous plaques covered by silvery scales**, commonly on extensor surfaces like elbows and knees. - It is a chronic inflammatory condition and does not manifest as acute target lesions or have a direct trigger by HSV outbreaks.

Q: Identify the skin condition shown in the image.

Ichthyosis Vulgaris. ***Ichthyosis Vulgaris*** - This condition is characterized by **fine, white-to-gray scales** and **dry skin**, particularly noticeable on the extensor surfaces of the limbs. - It often presents with **palmar hyperlinearity** and can worsen in dry, cold environments, matching the classic appearance for a common genetic skin disorder. *Syndromic Ichthyosis* - This category encompasses various forms of **ichthyosis associated with other systemic abnormalities** or symptoms beyond just skin manifestations. - Without additional clinical information or specific features of a recognized syndrome, it is a less likely diagnosis compared to the more common solitary presentation. *Leprosy (Hansen's Disease)* - **Leprosy** typically presents with **hypopigmented or reddish patches**, peripheral nerve involvement leading to sensory loss, and often **nodules or plaques**. - The appearance in this image does not show the characteristic nerve damage or inflammatory lesions associated with this infectious disease. *Sarcoidosis (Granulomatosis)* - **Sarcoidosis** is a multisystem **granulomatous disease** that can affect the skin, manifesting as **papules, nodules, plaques, or lupus pernio**. - The image does not display the typical granulomatous lesions or the characteristic morphology of sarcoidosis.

Q: Identify the skin lesion shown in the image.

Becker nevus. ***Becker nevus*** - This image clearly shows a large, **hyperpigmented patch with overlying coarse terminal hairs**, characteristic of a Becker nevus. - Becker nevi typically develop in adolescence and are often found on the shoulder or upper trunk, as seen here. *Hypopigmented macule* - A **hypopigmented macule** would appear as an area of skin with **reduced pigmentation** (lighter than the surrounding skin), which is contrary to the darker lesion shown. - There would also be no indication of **increased hair growth** within a typical hypopigmented macule. *Spitz nevus* - A Spitz nevus is a benign melanocytic nevus often appearing as a **dome-shaped, pink or red papule or nodule**, commonly on the face or limbs. - It does not present as a large, hairy, **hyperpigmented patch** as depicted in the image. *Epidermal nevus* - An epidermal nevus is a **congenital lesion** formed by an overgrowth of epidermal cells, but its appearance is typically a **verrucous (wart-like) plaque** or linearly arranged papules. - While it can be hyperpigmented, it generally **lacks the prominent hypertrichosis** (excessive hair growth) seen in the image.

Q: A known case of diabetes develops annular orange skin lesions that disappear after a biopsy. What is the term used to describe this phenomenon?

Reverse Koebner's phenomenon. ***Reverse Koebner's phenomenon*** - This phenomenon describes the **improvement or disappearance of skin lesions** at sites of trauma or biopsy, in contrast to the typical Koebner phenomenon where trauma induces new lesions. - In **necrobiosis lipoidica diabeticorum**, a condition associated with diabetes, annular orange lesions may temporarily resolve after trauma, which is characteristic of the reverse Koebner's phenomenon. *Koebner's phenomenon* - Also known as the **isomorphic phenomenon**, it involves the development of **new skin lesions** characteristic of a dermatosis at sites of trauma (e.g., psoriasis, lichen planus, vitiligo). - This is the opposite of what is described in the question, where lesions disappear after biopsy. *Asboe-Hansen sign* - Refers to the **extension of a blister** into previously unaffected skin when pressure is applied to the top of the blister. - This sign is typically observed in **blistering skin conditions** such as pemphigus and bullous pemphigoid, and is unrelated to the resolution of lesions after biopsy. *Isotopic phenomenon* - Describes the manifestation of a **new skin disease** at the site of a prior, unrelated, and already healed skin disease (e.g., herpes zoster followed by lichen planus in the same dermatome). - This phenomenon is not characterized by the disappearance of existing lesions following trauma.

Q: Normal epidermal turnover time is?

4 weeks. ***4 weeks*** - The normal epidermal turnover time, from the basal layer to the shedding of **stratum corneum** cells, is approximately **28 to 30 days**, or roughly 4 weeks. - This duration reflects the time it takes for a keratinocyte to mature and migrate through all layers of the **epidermis**. *1 week* - This period is too short for normal epidermal turnover, as it would suggest a much faster rate of keratinocyte proliferation and differentiation. - A turnover time of 1 week is characteristic of conditions like **psoriasis**, where the epidermal cell cycle is significantly accelerated. *2 weeks* - This timeframe is also shorter than the normal epidermal turnover, implying an accelerated cell cycle, though not as rapid as in conditions like psoriasis. - While cells start migrating earlier, their full maturation and shedding take longer than two weeks. *3 weeks* - While closer to the normal range, 3 weeks still slightly underestimates the full duration of epidermal turnover. - The complete process, including migration through the **stratum granulosum** and formation of a competent stratum corneum, typically extends to 4 weeks.

Q: What is the typical duration for pityriasis rosea to resolve?

6-12 weeks. ***6-12 weeks*** - **Pityriasis rosea** is a self-limiting skin condition that typically resolves spontaneously within **6-8 weeks**, though it may take up to 12 weeks in some cases. - The disease progression involves a **herald patch** (present in 50-90% of cases) followed by a generalized secondary eruption that gradually fades over this timeframe. - Most authoritative dermatology texts cite this as the **standard duration** for complete resolution. *1-2 weeks* - This duration is **far too short** for pityriasis rosea, as the secondary rash typically takes 1-2 weeks just to fully develop after the herald patch. - Complete resolution in this timeframe would be extremely unusual and should prompt consideration of alternative diagnoses. *2-4 weeks* - This timeframe is still **too short** for typical resolution, as most patients are still in the active phase of the eruption at 4 weeks. - This might represent the time from herald patch to peak of eruption, not complete resolution. *4-8 weeks* - While some mild cases may begin to resolve around 6-8 weeks, this range is generally considered the **minimum duration** rather than the typical course. - Most standard dermatology references cite 6-8 weeks to 12 weeks as the expected timeframe for complete resolution.

Q: Harlequin ichthyosis is caused by mutation of which gene?

ABCA12. ***ABCA12*** - **Harlequin ichthyosis** is a severe, life-threatening genetic skin disorder caused by mutations in the **ABCA12 gene**. - The **ABCA12 gene** encodes an ATP-binding cassette (ABC) transporter protein essential for lipid transport in keratinocytes, critical for epidermal barrier formation. - Mutations lead to defective lamellar granule lipid secretion, resulting in thick, plate-like scales and severe skin abnormalities present at birth. *FAD* - **FAD (Flavin Adenine Dinucleotide)** is a coenzyme, not a gene, making this an inappropriate option. - While FAD is involved in various metabolic redox reactions, it has no direct association with genetic causes of ichthyosis. *Keratin 1* - Mutations in **Keratin 1 (KRT1)** cause **epidermolytic hyperkeratosis** (epidermolytic ichthyosis), characterized by blistering and hyperkeratosis. - This is a different keratinization disorder with a distinct clinical presentation from harlequin ichthyosis. *ALOXE3* - Mutations in **ALOXE3** (arachidonate lipoxygenase 3) cause **autosomal recessive congenital ichthyosis (ARCI)**, also known as **lamellar ichthyosis**. - This presents with collodion membrane at birth and generalized scaling, but is less severe than harlequin ichthyosis.

Q: Patients with which of the following conditions are at greatest risk of pernio

Raynaud's phenomenon. ***Raynaud's phenomenon*** - Patients with **Raynaud's phenomenon** have an underlying **vasospastic disorder** where small arteries, especially in the fingers and toes, constrict in response to cold or stress. - This predisposition to **vasoconstriction** makes them more susceptible to developing pernio (chilblains), which is also a localized inflammatory lesion triggered by exposure to cold in susceptible individuals. *Kawasaki disease* - **Kawasaki disease** is a form of **vasculitis** primarily affecting children, characterized by fever, rash, conjunctivitis, and changes in the oral mucosa and extremities. [1] - While it affects blood vessels, its pathology and clinical manifestations are distinct from pernio, and it does not predispose individuals to chilblains. *Henoch-Schönlein purpura* - **Henoch-Schönlein purpura** (HSP) is a **small-vessel vasculitis** characterized by a classic tetrad of palpable purpura, arthritis, abdominal pain, and renal disease, predominantly affecting children. [1] - The mechanism of HSP involves IgA deposition in vessel walls and is not associated with an increased risk of pernio. *Hepatitis C infection* - **Hepatitis C infection** is a viral infection that primarily affects the liver but can have various **extrahepatic manifestations**, including mixed cryoglobulinemia, which causes vasculitis. [1] - While cryoglobulinemic vasculitis can lead to skin lesions, it is distinct from pernio, and hepatitis C infection itself does not directly increase the risk of developing pernio.

Question 1

A 45-year-old man presents with multiple firm, yellowish nodules on his extensor surfaces. What is the most likely diagnosis?

Accepted Answer

Xanthomas

Answer

Lipomas

Answer

Seborrheic keratosis

Answer

Erythema nodosum

Question 2

Which skin condition is characterized by a 'herald patch'?

Accepted Answer

Pityriasis rosea

Answer

Psoriasis

Answer

Lichen planus

Answer

Eczema

Question 3

A 30-year-old male presents with recurrent episodes of erythematous target-like lesions, primarily on the hands and forearms, often following herpes simplex outbreaks. What is the most likely diagnosis?

Accepted Answer

Erythema multiforme

Answer

Urticaria

Answer

Fixed drug eruption

Answer

Psoriasis

Question 4

Identify the skin condition shown in the image.

Accepted Answer

Ichthyosis Vulgaris

Answer

Syndromic Ichthyosis

Answer

Leprosy (Hansen's Disease)

Answer

Sarcoidosis (Granulomatosis)

Question 5

Identify the skin lesion shown in the image.

Accepted Answer

Becker nevus

Answer

Hypopigmented macule

Answer

Spitz nevus

Answer

Epidermal nevus

Question 6

A known case of diabetes develops annular orange skin lesions that disappear after a biopsy. What is the term used to describe this phenomenon?

Accepted Answer

Reverse Koebner's phenomenon

Answer

Koebner's phenomenon

Answer

Asboe-Hansen sign

Answer

Isotopic phenomenon

Question 7

Normal epidermal turnover time is?

Accepted Answer

4 weeks

Answer

1 week

Answer

2 weeks

Answer

3 weeks

Question 8

What is the typical duration for pityriasis rosea to resolve?

Accepted Answer

6-12 weeks

Answer

1-2 weeks

Answer

2-4 weeks

Answer

4-8 weeks

Question 9

Harlequin ichthyosis is caused by mutation of which gene?

Accepted Answer

ABCA12

Answer

FAD

Answer

Keratin 1

Answer

ALOXE3

Question 10

Patients with which of the following conditions are at greatest risk of pernio

Accepted Answer

Raynaud's phenomenon

Answer

Kawasaki disease

Answer

Hepatitis C infection

Answer

Henoch-Schönlein purpura

Basic Dermatology — MCQs

Basic Dermatology — MCQs

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