Basic Dermatology Practice Questions

Q: A 20-year-old woman presents with the sudden onset of red, target-shaped lesions on her palms and soles, following a herpes simplex outbreak. What is the likely diagnosis?

Erythema multiforme (EM). ***Erythema multiforme (EM)*** - This presentation is classic for **Erythema multiforme**, characterized by the acute onset of **target-shaped lesions** on the extremities, often precipitated by **herpes simplex virus (HSV) infection**. - The lesions on the **palms and soles** are a hallmark feature, distinguishing it from other skin conditions. *Stevens-Johnson syndrome (SJS)* - While SJS also involves skin lesions, it is a much more severe condition characterized by **extensive epidermal detachment** (often >10% of body surface area) and significant **mucosal involvement**. - SJS typically involves flu-like prodromal symptoms and is more commonly associated with drug reactions rather than HSV. *Pemphigus vulgaris (PV)* - Pemphigus vulgaris is an **autoimmune blistering disease** causing **flaccid bullae** and erosions on the skin and mucous membranes, often with Nikolsky's sign. - It does not typically present with target lesions nor is it triggered by HSV outbreaks. *Urticaria (hives)* - Urticaria presents as **transient, pruritic, raised wheals** (hives) that can appear anywhere on the body and blanch with pressure. - Unlike erythema multiforme, urticaria lesions are not typically target-shaped and do not commonly persist for days.

Q: A 30-year-old man presents with multiple painful, suppurative nodules in his axillae and groin, and he has a history of smoking. What is the most likely diagnosis?

Hidradenitis suppurativa. ***Hidradenitis suppurativa*** - This condition is characterized by **chronic inflammation** of the **apocrine glands**, presenting as painful, deep-seated nodules, abscesses, and sinus tracts in intertriginous areas like the **axillae and groin**. - **Smoking** is a significant risk factor, and the recurring nature of the lesions fits this diagnosis perfectly. *Furunculosis* - **Furunculosis** involves single or multiple painful, pus-filled lesions (boils) caused by bacterial infection of hair follicles, typically **Staphylococcus aureus**. - While furuncles can occur in the axillae and groin, they generally don't present as widespread, chronic, or deeply interconnected **nodules and sinus tracts** characteristic of the patient's presentation. *Lymphogranuloma venereum* - **Lymphogranuloma venereum (LGV)** is a sexually transmitted infection caused by specific serovars of **Chlamydia trachomatis**. - It primarily causes **genital ulcers**, **inguinal lymphadenopathy** (buboes), and proctitis, but does not present with the diffuse, suppurative nodules in the axillae seen in this case. *Erythrasma* - **Erythrasma** is a superficial skin infection caused by **Corynebacterium minutissimum**, characterized by well-demarcated, reddish-brown patches with fine scales, often in intertriginous areas. - It typically causes **asymptomatic or mildly itchy patches** and does not involve painful, suppurative nodules or abscesses.

Q: A 40-year-old man presents with thickened, erythematous skin exhibiting a cobblestone appearance on the lower legs. What is the most likely diagnosis?

Pretibial myxedema. ***Pretibial myxedema*** * **Pretibial myxedema** presents with **thickened, erythematous skin** on the lower legs, often described as having an "orange peel" or **cobblestone appearance**. * It is specifically associated with **Graves' disease** (hyperthyroidism) due to the deposition of hyaluronic acid and chondroitin sulfate. *Lichen planus* * **Lichen planus** typically manifests as **pruritic, purple, polygonal papules and plaques** (the "5 Ps") rather than thickened, cobblestoned skin. * It commonly affects the wrists, ankles, and oral mucosa, with a different characteristic morphology. *Venous stasis dermatitis* * **Venous stasis dermatitis** also affects the lower legs but presents with **reddish-brown discoloration**, **scaling**, itching, and sometimes ulceration due to chronic venous insufficiency. * The skin changes are more indicative of inflammation and poor circulation, not the distinct thickening or cobblestone texture of myxedema. *Chronic plaque psoriasis* * **Chronic plaque psoriasis** is characterized by well-demarcated, **erythematous plaques** covered with **silvery scales**, primarily affecting extensor surfaces (elbows, knees, scalp). * While it causes thickened skin, the appearance is scaly and not typically described as cobblestone or specifically located only in the pretibial area without other psoriatic manifestations.

Q: A 50-year-old male presents with multiple, waxy, brown, stuck-on lesions on his trunk. What is the most likely diagnosis?

Seborrheic keratosis. ***Seborrheic keratosis*** - This condition is characterized by **waxy**, **brown**, "stuck-on" lesions, perfectly matching the description. - They are common, **benign epidermal tumors** that typically appear in middle to older age on the trunk, face, or scalp. *Actinic keratosis* - These are **pre-malignant lesions** that are usually rough, scaly patches on sun-exposed skin. - They lack the "stuck-on" appearance and waxy texture described in the patient. *Melanoma* - Melanoma is a **malignant skin cancer** that typically presents as an asymmetrical, irregularly bordered, multi-colored lesion with a changing diameter. - While it can be dark, it usually doesn't have the waxy, "stuck-on" quality of seborrheic keratoses. *Basal cell carcinoma* - This is the most common form of **skin cancer**, often appearing as a pearly nodule with rolled borders, telangiectasias, or a non-healing sore. - It does not present with multiple, waxy, brown, "stuck-on" lesions as 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: Which skin condition is associated with ash leaf spots?

Tuberous sclerosis. ***Tuberous sclerosis*** - **Ash leaf spots** (hypopigmented macules) are a characteristic **cutaneous finding** in tuberous sclerosis, often present from birth. - Tuberous sclerosis is a **neurocutaneous syndrome** also associated with **facial angiofibromas**, **ungual fibromas**, and neurological symptoms like seizures. *Neurofibromatosis* - Characterized by **café-au-lait spots**, which are hyperpigmented macules, not hypopigmented ash leaf spots. - Also associated with **neurofibromas** and **Lisch nodules** (hamartomas of the iris). *Sturge-Weber syndrome* - Primarily presents with a **port-wine stain (facial nevus flammeus)**, which is a vascular malformation, typically unilateral on the face. - Associated with **leptomeningeal angioma** and often causes seizures and glaucoma. *Von Hippel-Lindau disease* - This condition involves the development of **tumors** in various organs, such as **hemangioblastomas** in the brain, spinal cord, and retina, and **renal cell carcinoma**. - It does not characteristically present with skin lesions like ash leaf spots.

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 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: 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: 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.

Question 1

A 20-year-old woman presents with the sudden onset of red, target-shaped lesions on her palms and soles, following a herpes simplex outbreak. What is the likely diagnosis?

Accepted Answer

Erythema multiforme (EM)

Answer

Stevens-Johnson syndrome (SJS)

Answer

Pemphigus vulgaris (PV)

Answer

Urticaria (hives)

Question 2

A 30-year-old man presents with multiple painful, suppurative nodules in his axillae and groin, and he has a history of smoking. What is the most likely diagnosis?

Accepted Answer

Hidradenitis suppurativa

Answer

Furunculosis

Answer

Lymphogranuloma venereum

Answer

Erythrasma

Question 3

A 40-year-old man presents with thickened, erythematous skin exhibiting a cobblestone appearance on the lower legs. What is the most likely diagnosis?

Accepted Answer

Pretibial myxedema

Answer

Lichen planus

Answer

Venous stasis dermatitis

Answer

Chronic plaque psoriasis

Question 4

A 50-year-old male presents with multiple, waxy, brown, stuck-on lesions on his trunk. What is the most likely diagnosis?

Accepted Answer

Seborrheic keratosis

Answer

Actinic keratosis

Answer

Melanoma

Answer

Basal cell carcinoma

Question 5

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

Accepted Answer

Pityriasis rosea

Answer

Psoriasis

Answer

Lichen planus

Answer

Eczema

Question 6

Which skin condition is associated with ash leaf spots?

Accepted Answer

Tuberous sclerosis

Answer

Neurofibromatosis

Answer

Sturge-Weber syndrome

Answer

Von Hippel-Lindau disease

Question 7

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 8

Identify the skin lesion shown in the image.

Accepted Answer

Becker nevus

Answer

Hypopigmented macule

Answer

Spitz nevus

Answer

Epidermal nevus

Question 9

Normal epidermal turnover time is?

Accepted Answer

4 weeks

Answer

1 week

Answer

2 weeks

Answer

3 weeks

Question 10

Harlequin ichthyosis is caused by mutation of which gene?

Accepted Answer

ABCA12

Answer

FAD

Answer

Keratin 1

Answer

ALOXE3

Basic Dermatology — MCQs

Basic Dermatology — MCQs

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