Basic Dermatology Practice Questions

Q: A 22-year-old woman presents with multiple tender, erythematous nodules on her shins that developed over the past week. She reports having a sore throat 2 weeks ago. She also complains of joint pain and fatigue. Physical examination reveals raised, red, tender nodules on the anterior surface of both legs. Her temperature is 38.2°C. Which of the following is the most likely diagnosis?

Erythema nodosum. ***Erythema nodosum*** - The presentation of **tender, erythematous nodules on the shins**, following a preceding **sore throat**, with associated **joint pain and fatigue**, is highly characteristic of **erythema nodosum**. - It is a form of **panniculitis** typically triggered by infections (e.g., streptococcal pharyngitis), medications, or systemic diseases. *Cellulitis* - Characterized by a **warm, erythematous, swollen area** with poorly defined borders, often accompanied by pain and fever, but typically presents as a diffuse skin infection rather than distinct nodules. - While fever is present, the **nodular nature** of the lesions and their bilateral, symmetrical distribution are less consistent with cellulitis. *Sweet syndrome* - Also known as acute febrile neutrophilic dermatosis, it presents with **tender erythematous plaques or nodules** and **fever**, but typically has a more prominent **neutrophilic infiltrate** histologically. - Lesions of Sweet syndrome often appear on the **upper extremities, face, or neck**, and while it can affect the shins, the clinical picture here is more classic for erythema nodosum, especially given the history of sore throat. *Superficial thrombophlebitis* - Presents as a **palpable, tender, erythematous cord** along the course of a superficial vein, often with localized swelling and warmth. - The lesions are typically **linear or cord-like**, not discrete nodules scattered over the shins, and are directly related to a thrombosed vein.

Q: A 28-year-old Caucasian woman presents to a local walk-in clinic with the complaint of pruritus and a salmon-colored scaling patch on her back. The patient stated that she developed a cold a couple of weeks ago and that her skin lesion has enlarged in the last week. The past medical history is unremarkable. The physical examination reveals a generalized exanthem, bilateral symmetric macules pointing towards the cleavage lines, and a salmon-colored patch on her back, with a well-demarcated border containing a collarette with fine-scale. What is the best next step of management in this case?

Pruritus control and reassurance. ***Pruritus control and reassurance*** - This patient's presentation, including a prior **cold**, a **salmon-colored scaling patch** (herald patch), and a generalized rash with lesions pointing toward **skin cleavage lines** (Christmas tree pattern), is highly suggestive of **pityriasis rosea**. - Pityriasis rosea is a benign, self-limiting condition that typically resolves spontaneously within 6-8 weeks, making symptomatic treatment for pruritus and reassurance the appropriate initial management. - Management includes **emollients**, **oral antihistamines**, and **topical corticosteroids** if needed for pruritus control. *Phototherapy* - While phototherapy, particularly **UVB**, can be used for widespread or persistent pityriasis rosea, it is generally considered for more severe cases or when symptomatic relief with topical treatments is insufficient. - It is not usually the **first-line step** given the self-limiting nature of the condition and the patient's relatively recent onset. *Systemic steroid therapy* - **Systemic steroids** are rarely needed for pityriasis rosea, as the condition is self-limiting and only causes mild discomfort in most cases. - Their use carries potential side effects and is reserved for **severe, widespread disease** with intense pruritus not responding to other therapies. *Beta-lactam therapy* - Pityriasis rosea is thought to have a **viral etiology** (possibly HHV-6 or HHV-7), not bacterial, so **antibiotic therapy** like beta-lactams would be ineffective. - There is no indication of a bacterial infection in the patient's presentation.

Q: What is the name of this appearance which is seen in pellagra?

Casal's necklace. ***Casal's necklace*** - Characteristic of **pellagra**, it presents as a **dermatitis** localized around the neck in a "necklace" pattern due to **niacin (vitamin B3) deficiency**. - This sign is commonly associated with the classic triad of pellagra: **dermatitis**, **diarrhea**, and **dementia**. *Shawl sign* - This sign is associated with **dermatomyositis** and refers to a **macular erythema** distributed over the upper back, shoulders, and posterior neck in a shawl-like pattern. - It is not related to pellagra or **niacin deficiency**, and should not be confused with Casal's necklace. *Gottron's papule* - These are **violaceous papules** seen over the dorsal interphalangeal joints in **dermatomyositis**, characterized by flat-topped, scaly lesions on the fingers. - Their appearance is associated with **proximal muscle weakness** and other features of dermatomyositis, rather than **niacin deficiency**. *Burn* - Refers to an injury from thermal exposure and does not relate to the **dermatological signs** of pellagra. - It is not a clinical feature and does not reflect the **nutritional deficiency** seen in this condition.

Q: What are these horizontal lines seen on the skin called?

Blaschko lines. ***Blaschko lines*** - **Blaschko lines** are invisible lines of normal skin development, thought to represent migration paths of **epidermal cells** during embryogenesis. - They become visible in certain skin conditions, such as **pigmentary disorders (e.g., incontinentia pigmenti)** and **linear epidermal nevi**, manifesting as distinctive linear or whorled patterns. *Dermatomes* - **Dermatomes** represent areas of skin innervated by a single **spinal nerve root**. - Conditions like **herpes zoster (shingles)** follow a dermatomal pattern. *Vascular development* - **Vascular development** refers to the formation of blood vessels, which are crucial for oxygen and nutrient delivery. - Anomalies in vascular development lead to conditions like **hemangiomas** or **vascular malformations**. *Lymphatic development* - **Lymphatic development** involves the formation of the lymphatic system, important for fluid balance and immune function. - Abnormalities can result in **lymphedema** or **lymphatic malformations**.

Q: Wood's lamp is not used for diagnosing:

Lichen planus. ***Lichen planus*** - **Wood's lamp** is generally not used for diagnosing **lichen planus** as the lesions typically do not fluoresce. - Diagnosis of lichen planus relies on its characteristic **violaceous, polygonal, pruritic papules and plaques** and often confirmed by **biopsy**. *Pityriasis versicolor* - **Wood's lamp** is useful for **pityriasis versicolor**, causing it to fluoresce a **yellowish-green or coppery-orange** color due to metabolic byproducts of *Malassezia* fungi. - This characteristic fluorescence helps in differentiating lesions from other skin conditions and in identifying subclinical involvement. *Porphyria* - **Wood's lamp** can be used to detect **reddish-pink fluorescence of urine** or skin in patients with **porphyria cutanea tarda** due to the accumulation of porphyrins. - This fluorescence is a key diagnostic indicator in certain types of **porphyria**, particularly those affecting the skin. *Vitiligo* - **Wood's lamp** enhances the contrast between depigmented and normally pigmented skin, making **vitiligo** lesions appear **bright bluish-white** due to the absence of melanin. - It is particularly useful for detecting subtle or small lesions of **vitiligo**, especially in individuals with lighter skin tones.

Q: Granular layer is absent in:

Ichthyosis vulgaris. ***Ichthyosis vulgaris*** - A key **histopathological feature** of ichthyosis vulgaris is the **absence or marked thinning of the granular layer** of the epidermis. - This, combined with **hyperkeratosis**, contributes to the characteristic dry, scaly skin presentation. *Lamellar ichthyosis* - This condition typically presents with a **normal or thickened granular layer**, along with marked **orthokeratotic hyperkeratosis**. - The thickened granular layer is not a distinguishing feature for absence in lamellar ichthyosis. *Epidermolytic hyperkeratosis* - Histologically, this disorder is characterized by **epidermolytic changes**, meaning abnormal vacuolization and clumping of keratin filaments in suprabasal keratinocytes, and it **does not typically involve the absence of the granular layer**. - Instead, the granular layer can be present or even thickened, alongside specific cellular changes. *X-linked ichthyosis* - This condition is characterized by a **normal granular layer**, but striking **compact hyperkeratosis** due to a deficiency in steroid sulfatase. - The absence of the granular layer is not a feature of X-linked ichthyosis.

Q: Diascopy is very helpful in the diagnosis of:

All of the options. ***All of the options*** - Diascopy is a diagnostic technique using a glass slide to apply pressure on skin lesions, helping differentiate between **vascular (erythematous)** and **non-vascular lesions** and revealing underlying pathology. - It is particularly helpful in diagnosing **lupus vulgaris**, **cutaneous vasculitis**, and **nevus anaemicus**. *Lupus vulgaris* - Shows pathognomonic **apple-jelly nodules** on diascopy due to granulomatous inflammation. - When pressed with a glass slide, the lesion reveals a characteristic **translucent yellowish-brown ("apple jelly") color** from tuberculoid granulomas. *Cutaneous vasculitis* - Diascopy differentiates **purpura (extravasated blood)** from simple erythema. - **Non-blanching purpura** indicates intravascular hemorrhage from vessel wall damage, a key feature of vasculitis. - Blanching erythema would suggest vasodilation rather than true vasculitis. *Nevus anaemicus* - Diascopy causes the pale lesion to **disappear or blend** with surrounding blanched normal skin. - This occurs because normal surrounding vessels constrict under pressure, matching the baseline pale appearance of the nevus. - This helps distinguish it from other hypopigmented lesions like vitiligo (which remains visible on diascopy).

Q: Which is a secondary skin lesion?

Scales. ***Scales*** - **Scales** are a classic example of a **secondary skin lesion**, formed by the shedding of excess dead epidermal cells. - They result from **primary inflammatory processes** that alter normal skin maturation and shedding, such as psoriasis or eczema. - Scales represent accumulation of stratum corneum and are a modification of the skin surface. *Plaque* - A **plaque** is typically a **primary skin lesion** defined as a raised, flat-topped lesion greater than 1 cm in diameter. - However, plaques can also form as **secondary lesions when multiple papules coalesce**. - In this context, as a single lesion arising directly from a disease process like **psoriasis**, it is considered primary. *Macule* - A **macule** is a **primary skin lesion**, characterized as a circumscribed, flat area of discoloration less than 1 cm in diameter. - It represents a change in skin color without elevation or depression, such as **freckles** or **petechiae**. *Abscess* - While sometimes listed variably, an **abscess** is more accurately considered a **secondary lesion** in most dermatology classifications. - It represents a localized collection of **pus** within the dermis or subcutaneous tissue that develops from the breakdown of tissue following infection. - However, **scales** remain the more classic and unambiguous example of a secondary lesion among these options.

Q: Perleche is caused by:

Loss of vertical dimension. ***Loss of vertical dimension*** - **Loss of vertical dimension** leads to over-closure of the mouth, causing the corners of the mouth to become folded and moist. - This moisture and skin folding create an ideal environment for **candidal** or **bacterial colonization**, leading to perleche. *Trauma to the corners of the mouth* - While trauma can cause lesions, it is not the primary or typical cause for the chronic, often bilateral, inflammation seen in perleche. - Trauma alone would not explain the characteristic **fissuring** and **erythema** associated with moisture accumulation. *Lack of Vitamin C* - A lack of Vitamin C (scurvy) primarily causes **gingival bleeding**, **poor wound healing**, and **petechiae**. - It does not directly cause the characteristic angular cheilitis seen in perleche. *Maintained vertical dimension* - A maintained or adequate vertical dimension would prevent the over-closure and skin folding that contributes to the moist environment at the oral commissures. - Therefore, it is a healthy state that typically works against the development of perleche.

Q: Keratodermic sandals is a feature of ?

Pityriasis rubra pilaris. ***Pityriasis rubra pilaris*** - **Keratodermic sandals** describe the characteristic **thickening and orange-red discoloration** of the soles of the feet seen in **pityriasis rubra pilaris (PRP)**. - This finding is specific to PRP and helps distinguish it from other dermatological conditions. *Psoriasis* - While psoriasis can cause **palmar-plantar keratoderma**, it typically presents with **silvery scales** and well-demarcated erythematous plaques, not the "keratodermic sandals" pattern. - The thickened skin in psoriasis is often less uniformly orange-red and more scaly than in PRP. *Lichen planus* - Lichen planus characteristically presents with **pruritic, polygonal, purple, planar papules and plaques** (**the 6 P's**), often with Wickham's striae. - It does not typically cause the diffuse orange-red palmoplantar thickening described as keratodermic sandals. *Pityriasis rosea* - Pityriasis rosea is characterized by a "herald patch" followed by a diffuse rash with a **Christmas tree pattern** on the trunk. - It does not involve significant palmoplantar involvement or the "keratodermic sandals" appearance.

Question 1

A 22-year-old woman presents with multiple tender, erythematous nodules on her shins that developed over the past week. She reports having a sore throat 2 weeks ago. She also complains of joint pain and fatigue. Physical examination reveals raised, red, tender nodules on the anterior surface of both legs. Her temperature is 38.2°C. Which of the following is the most likely diagnosis?

Accepted Answer

Erythema nodosum

Answer

Cellulitis

Answer

Sweet syndrome

Answer

Superficial thrombophlebitis

Question 2

A 28-year-old Caucasian woman presents to a local walk-in clinic with the complaint of pruritus and a salmon-colored scaling patch on her back. The patient stated that she developed a cold a couple of weeks ago and that her skin lesion has enlarged in the last week. The past medical history is unremarkable. The physical examination reveals a generalized exanthem, bilateral symmetric macules pointing towards the cleavage lines, and a salmon-colored patch on her back, with a well-demarcated border containing a collarette with fine-scale. What is the best next step of management in this case?

Accepted Answer

Pruritus control and reassurance

Answer

Phototherapy

Answer

Systemic steroid therapy

Answer

Beta-lactam therapy

Question 3

What is the name of this appearance which is seen in pellagra?

Accepted Answer

Casal's necklace

Answer

Shawl sign

Answer

Gottron's papule

Answer

Burn

Question 4

What are these horizontal lines seen on the skin called?

Accepted Answer

Blaschko lines

Answer

Dermatomes

Answer

Vascular development

Answer

Lymphatic development

Question 5

Wood's lamp is not used for diagnosing:

Accepted Answer

Lichen planus

Answer

Pityriasis versicolor

Answer

Porphyria

Answer

Vitiligo

Question 6

Granular layer is absent in:

Accepted Answer

Ichthyosis vulgaris

Answer

Lamellar ichthyosis

Answer

Epidermolytic hyperkeratosis

Answer

X linked ichthyosis

Question 7

Diascopy is very helpful in the diagnosis of:

Accepted Answer

All of the options

Answer

Lupus vulgaris

Answer

Cutaneous vasculitis

Answer

Nevus anaemicus

Question 8

Which is a secondary skin lesion?

Accepted Answer

Scales

Answer

Plaque

Answer

Macule

Answer

Abscess

Question 9

Perleche is caused by:

Accepted Answer

Loss of vertical dimension

Answer

Trauma to the corners of the mouth

Answer

Lack of Vitamin C

Answer

Maintained vertical dimension

Question 10

Keratodermic sandals is a feature of ?

Accepted Answer

Pityriasis rubra pilaris

Answer

Psoriasis

Answer

Lichen planus

Answer

Pityriasis rosea

Basic Dermatology — MCQs

Basic Dermatology — MCQs

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