Blistering Diseases Practice Questions

Q: Which of the following is NOT a typical feature of erythema multiforme?

Nikolsky sign. ***Nikolsky sign*** - The **Nikolsky sign** involves the detachment of the superficial epidermis from the basal layer when lateral pressure is applied to seemingly uninvolved skin, indicative of severe blistering diseases like **pemphigus vulgaris** or **toxic epidermal necrolysis (TEN)**, but not typically **erythema multiforme (EM)**. - While EM can involve blistering, the characteristic mechanism of epidermal detachment that produces a positive Nikolsky sign is not a feature of its pathogenesis. *Triggered by HSV* - **Herpes simplex virus (HSV) infection** is the most common precipitating factor for **erythema multiforme**, particularly in its recurrent form (erythema multiforme minor). - An immune response to viral antigens deposited in the skin is thought to drive the characteristic skin lesions. *Mucosal involvement* - **Mucosal involvement** is a common feature, especially in **erythema multiforme major**, affecting the oral cavity, eyes, and/or anogenital region. - This can manifest as painful erosions and ulcers, contributing to significant morbidity. *Target lesions* - **Target lesions**, with their characteristic concentric rings of color (erythematous outer ring, pale edematous middle ring, and dusky or vesicular center), are the **hallmark skin lesion** of erythema multiforme. - These lesions are typically fixed and symmetrically distributed, often on the extremities.

Q: A 30-year-old woman presents with blistering on her hands after sun exposure. She has a history of alcohol use disorder. Laboratory tests show elevated liver enzymes and low serum haptoglobin. Analyze the clinical scenario to identify the most likely diagnosis.

Porphyria cutanea tarda. ***Porphyria cutanea tarda*** - **Blistering on sun-exposed areas** (hands) and a history of **alcohol use disorder** are classic presentations of PCT. - **Elevated liver enzymes** support the diagnosis, as PCT is strongly associated with liver disease, alcohol use, hepatitis C, and iron overload. - PCT is the most common porphyria and results from deficiency of uroporphyrinogen decarboxylase (UROD), leading to accumulation of photosensitizing porphyrins in the skin. *Pemphigus vulgaris (PV)* - Presents with **flaccid blisters** and erosions primarily affecting the **mucous membranes** and skin, often without a strong association with sun exposure. - Diagnosis is confirmed by **direct immunofluorescence** showing anti-desmoglein antibodies, and generally not associated with liver enzyme abnormalities or alcohol use. *Dermatitis herpetiformis (DH)* - Characterized by **intensely pruritic vesicles** and papules, mainly on extensor surfaces (elbows, knees, buttocks), strongly associated with **celiac disease** and gluten sensitivity. - While it is a blistering disease, sun exposure is not a primary trigger, nor are liver enzyme abnormalities or alcohol use typical associations. *Systemic lupus erythematosus (SLE)* - Photosensitivity can cause skin lesions, but typically presents as a **malar rash** or discoid lesions, not vesiculobullous eruptions. - It is a systemic autoimmune disease with diverse manifestations, but **blistering due to sun exposure** as the primary finding is not characteristic of SLE.

Q: Which of the following is the most characteristic feature of porphyria cutanea tarda (PCT)?

Is the most common type of human porphyria. ***Is the most common type of human porphyria*** - **Porphyria cutanea tarda (PCT)** is indeed the **most prevalent** type of porphyria, accounting for approximately 80% of all cases. - It is often acquired, triggered by factors such as **alcohol consumption** and **hepatitis C infection**, leading to its high incidence. *Is treated primarily with high-dose antimalarial drugs* - While antimalarial drugs like **hydroxychloroquine** or **chloroquine** are used for treatment, they are given in **low doses** to avoid exacerbating symptoms. - The primary treatment involves **phlebotomy** to reduce iron stores, which contribute to the disease. *Is caused by increased activity of uroporphyrinogen decarboxylase* - **PCT** is caused by a **deficiency** (decreased activity) of the enzyme **uroporphyrinogen decarboxylase (UROD)**, not increased activity. - This enzyme deficiency leads to the accumulation of **porphyrinogens**, which are then oxidized to photoactive porphyrins. *Is more common in children than adults* - **PCT** predominantly affects **adults**, typically presenting in the fourth to sixth decades of life. - Childhood cases are rare and usually associated with the familial form of the disease.

Q: A 22-year-old female presents with a history of multiple small grouped vesicles on her forearm and trunk. She reports a history of celiac disease. What is the most likely diagnosis?

Dermatitis herpetiformis. ***Dermatitis herpetiformis*** - The presentation of **multiple small grouped vesicles** on the **forearm and trunk** in a patient with a history of **celiac disease** is classic for dermatitis herpetiformis. - This condition is characterized by intense **itching** and the presence of **IgA deposits** in the dermal papillae, which are strongly associated with gluten sensitivity. *Pemphigus vulgaris* - Pemphigus vulgaris typically presents with **flaccid bullae** that easily **rupture**, forming erosions, often involving mucous membranes. - It is an **autoimmune blistering disease** mediated by **IgG autoantibodies** against desmoglein 1 and 3, not associated with celiac disease. *Bullous impetigo* - Bullous impetigo is a **bacterial skin infection** characterized by **large, flaccid bullae** that typically appear in children. - It is caused by *Staphylococcus aureus* and is usually accompanied by **honey-colored crusts** upon rupture, unlike the small, grouped vesicles seen here. *Herpes simplex virus infection* - Herpes simplex virus (HSV) infection causes **grouped vesicles** on an **erythematous base**, often around the mouth or genitals. - While grouped vesicles are a feature, the **widespread distribution** on the forearm and trunk in a patient with celiac disease makes HSV less likely; HSV lesions typically recur in the same localized area.

Q: A 35-year-old man with a history of celiac disease develops cutaneous bullae on his forearms and shoulders. Histopathology shows IgA deposits at the dermal-epidermal junction. What condition is most likely?

Dermatitis herpetiformis. ***Dermatitis herpetiformis*** - The presence of **granular IgA deposits** in the **dermal papillae** (papillary dermis tips) and a history of **celiac disease** are pathognomonic for dermatitis herpetiformis. - This condition presents with intensely **pruritic vesicles** and **bullae**, often on extensor surfaces like the forearms and shoulders. - Associated with **celiac disease** in 90-95% of cases, even if asymptomatic. *Bullous pemphigoid* - Characterized by **IgG autoantibodies** targeting **hemidesmosomes** (BP180 and BP230), leading to subepidermal bullae. - Direct immunofluorescence shows **linear IgG and C3 deposits** along the basement membrane zone, not IgA. *Pemphigus vulgaris* - Involves **IgG autoantibodies** against **desmogleins 1 and 3**, causing intraepidermal blistering (acantholysis). - Direct immunofluorescence reveals a characteristic "**fish-net**" or "**chicken-wire**" pattern of **IgG and C3** deposits throughout the epidermis. *Erythema multiforme* - A **hypersensitivity reaction** often triggered by infections (e.g., **HSV**, **Mycoplasma**) or drugs, presenting with target lesions. - Histopathology shows a **lymphocytic infiltrate** targeting keratinocytes and interface dermatitis, without characteristic IgA deposits.

Q: IgA deposition at the dermoepidermal junction is seen in?

Linear IgA disease. ***Linear IgA disease*** - This condition is characterized by a **linear deposition of IgA** at the **dermoepidermal junction**, visible on direct immunofluorescence (DIF). - The IgA deposition occurs along the **basement membrane zone**, leading to subepidermal blistering. *Dermatitis herpetiformis* - This autoimmune blistering disease is characterized by **granular IgA deposits** in the **dermal papillae**, not a linear pattern at the dermoepidermal junction. - It is strongly associated with **celiac disease** and presents with intensely pruritic vesicles. *Bullous pemphigoid* - This condition involves **linear deposition of IgG and/or C3** at the dermoepidermal junction, targeting hemidesmosomes. - While it features a linear pattern at the junction, the primary immunoglobulin involved is **IgG**, not IgA. *Epidermolysis bullosa* - This is a group of **inherited mechanobullous diseases** caused by genetic defects in structural proteins of the skin, leading to fragile skin that blisters easily with minor trauma. - It does **not involve immune-mediated deposition of IgA** or other immunoglobulins at the dermoepidermal junction.

Q: Which type of collagen is mutated in dystrophic epidermolysis bullosa?

Type VII. ***Type VII*** - **Type VII collagen** forms **anchoring fibrils** that connect the epidermis to the dermis at the dermal-epidermal junction, providing essential skin integrity. - Mutations in the gene encoding type VII collagen (**COL7A1**) lead to **dystrophic epidermolysis bullosa (DEB)**, characterized by severe blistering and skin fragility due to poor dermal-epidermal adhesion. - Note: Other forms of epidermolysis bullosa involve different proteins (e.g., keratins in EB simplex, laminin-332 in junctional EB). *Type I* - **Type I collagen** is the most abundant collagen in the body, found in **skin, bone, tendons, and ligaments**. - Mutations in type I collagen are primarily associated with conditions like **osteogenesis imperfecta**, causing brittle bones, not epidermolysis bullosa. *Type II* - **Type II collagen** is predominantly found in **cartilage**, making up the structural framework of hyaline cartilage. - Mutations in type II collagen are linked to **chondrodysplasias** and other skeletal disorders affecting cartilage development, not skin blistering. *Type IV* - **Type IV collagen** is a major component of **basement membranes**, providing structural support and filtration in various tissues. - Mutations in type IV collagen are associated with conditions like **Alport syndrome** (kidney/ear disease), not dystrophic epidermolysis bullosa.

Q: Which of the following drug classes is commonly implicated in causing Stevens-Johnson syndrome?

Antibiotics. ***Antibiotics*** - **Antibiotics**, particularly **sulfonamides** (e.g., sulfamethoxazole-trimethoprim) and **beta-lactams** (e.g., penicillins, cephalosporins), are among the most common drug classes implicated in causing **Stevens-Johnson Syndrome (SJS)**. - SJS is a severe **idiosyncratic drug reaction**, and many antibiotics can trigger this immune-mediated response. - **Note:** Other major causative drug classes include **anticonvulsants** (carbamazepine, phenytoin, lamotrigine), **allopurinol**, and **NSAIDs**, but among the options listed, antibiotics are the most commonly implicated. *Corticosteroids* - **Corticosteroids** are typically used in the **treatment** of SJS to suppress the immune response and reduce inflammation, not to cause it. - While they have their own set of side effects, initiating SJS is not one of their known adverse reactions. *Antifungals* - Although some **antifungals** can cause adverse drug reactions, they are **not typically associated** with SJS compared to antibiotics, anticonvulsants, or allopurinol. - The risk of SJS with antifungal medications is generally very low. *Proton pump inhibitors* - **Proton pump inhibitors (PPIs)** are generally well-tolerated and are **rarely implicated** as a cause of SJS. - Their primary side effects are usually gastrointestinal and not severe dermatological reactions.

Q: All of the following diseases cause intraepidermal bullae except:

Herpes gestationalis. ***Herpes gestationalis.*** - Herpes gestationalis is characterized by **urticarial papules** and vesicles, typically occurs in pregnancy, and does not form **intraepidermal bullae**. - This condition is linked more with **dermatitis herpetiformis** rather than with the intraepidermal blistering seen in the other options [2]. *Herpes zoster* - Herpes zoster causes **vesicular lesions** that are often grouped, presenting as painful **erythematous vesicles** along a dermatome. - The lesions can form intraepidermal bullae due to the **varicella-zoster virus** affecting the skin [1]. *Miliaria rubra* - Miliaria rubra, or **heat rash**, results from occluded sweat glands leading to **superficial vesicles or papules** in the epidermis. - The lesions may resemble blisters but are not true intraepidermal bullae and are prominent in hot, humid conditions. *Pemphigus* - Pemphigus is an autoimmune disorder causing **flaccid bullae** due to **acantholysis** in the epidermis, leading to intraepidermal bulla formation [3]. - It is characterized by **painful, fragile blisters** that rupture easily, differentiating it from other conditions listed [3]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, p. 366. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, pp. 1172-1174. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, pp. 1170-1172.

Question 1

Which of the following is NOT a typical feature of erythema multiforme?

Accepted Answer

Nikolsky sign

Answer

Triggered by HSV

Answer

Mucosal involvement

Answer

Target lesions

Question 2

A 30-year-old woman presents with blistering on her hands after sun exposure. She has a history of alcohol use disorder. Laboratory tests show elevated liver enzymes and low serum haptoglobin. Analyze the clinical scenario to identify the most likely diagnosis.

Accepted Answer

Porphyria cutanea tarda

Answer

Pemphigus vulgaris (PV)

Answer

Dermatitis herpetiformis (DH)

Answer

Systemic lupus erythematosus (SLE)

Question 3

Which of the following is the most characteristic feature of porphyria cutanea tarda (PCT)?

Accepted Answer

Is the most common type of human porphyria

Answer

Is treated primarily with high-dose antimalarial drugs

Answer

Is caused by increased activity of uroporphyrinogen decarboxylase

Answer

Is more common in children than adults

Question 4

A 22-year-old female presents with a history of multiple small grouped vesicles on her forearm and trunk. She reports a history of celiac disease. What is the most likely diagnosis?

Accepted Answer

Dermatitis herpetiformis

Answer

Pemphigus vulgaris

Answer

Bullous impetigo

Answer

Herpes simplex virus infection

Question 5

A 35-year-old man with a history of celiac disease develops cutaneous bullae on his forearms and shoulders. Histopathology shows IgA deposits at the dermal-epidermal junction. What condition is most likely?

Accepted Answer

Dermatitis herpetiformis

Answer

Bullous pemphigoid

Answer

Pemphigus vulgaris

Answer

Erythema multiforme

Question 6

IgA deposition at the dermoepidermal junction is seen in?

Accepted Answer

Linear IgA disease

Answer

Dermatitis herpetiformis

Answer

Bullous pemphigoid

Answer

Epidermolysis bullosa

Question 7

Which type of collagen is mutated in dystrophic epidermolysis bullosa?

Accepted Answer

Type VII

Answer

Type I

Answer

Type II

Answer

Type IV

Question 8

Acantholysis is not seen in:

Accepted Answer

Lichen planus

Answer

Dermatitis herpetiformis

Answer

Hailey-Hailey disease

Answer

Bullous pemphigoid

Question 9

Which of the following drug classes is commonly implicated in causing Stevens-Johnson syndrome?

Accepted Answer

Antibiotics

Answer

Corticosteroids

Answer

Antifungals

Answer

Proton pump inhibitors

Question 10

All of the following diseases cause intraepidermal bullae except:

Accepted Answer

Herpes gestationalis

Answer

Miliaria rubra

Answer

Herpes zoster

Answer

Pemphigus

Blistering Diseases — MCQs

Blistering Diseases — MCQs

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