A 26-year-old woman started carbamazepine for trigeminal neuralgia 4 weeks ago. She now has fever of 39°C, facial swelling, a widespread itchy morbilliform rash and cervical lymphadenopathy. Mucosae are spared and there is no blistering. Eosinophils 2,100/µL, ALT 310 U/L. What is the most likely diagnosis?

Drug reaction with eosinophilia and systemic symptoms

Acute generalised exanthematous pustulosis

A 45-year-old woman has flaccid blisters and raw erosions on her trunk. When the resident applies firm sliding pressure with a finger on normal-looking skin next to a lesion, the upper epidermis shears off. What does this positive sign indicate?

Loss of cohesion within the epidermis

A split at the basement membrane zone

Mast cell degranulation in the dermis

Fragility of dermal blood vessels

A 58-year-old man with chronic lymphocytic leukaemia has had severe, painful erosions of the lips, tongue and buccal mucosa for 2 months that have not responded to oral steroids, with bilateral conjunctivitis. His skin shows a mix of flaccid blisters, target-like lesions and lichenoid papules, including on the palms. Which test best supports the most likely diagnosis?

Indirect immunofluorescence on rat bladder epithelium

Indirect immunofluorescence on salt-split skin

Tzanck smear for multinucleated giant cells

Serum anti-tissue transglutaminase IgA

A 25-year-old woman is admitted with toxic epidermal necrolysis involving 40% of her body surface area, 10 days after starting co-trimoxazole for a urinary infection. She is haemodynamically stable. What is the most appropriate initial management?

Stop co-trimoxazole and give burns-unit supportive care

Routine prophylactic broad-spectrum IV antibiotics

Continue co-trimoxazole with IV steroid cover

Silver sulfadiazine dressings to all raw areas

Bullous disorders and drug reactions

20 NEET-PG practice questions on Bullous disorders and drug reactions, part of Dermatology. The first 20 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Medium
A 26-year-old woman started carbamazepine for trigeminal neuralgia 4 weeks ago. She now has fever of 39°C, facial swelling, a widespread itchy morbilliform rash and cervical lymphadenopathy. Mucosae are spared and there is no blistering. Eosinophils 2,100/µL, ALT 310 U/L. What is the most likely diagnosis?
1. ADrug reaction with eosinophilia and systemic symptoms
2. BStevens-Johnson syndrome
3. CAcute generalised exanthematous pustulosis
4. DFixed drug eruption
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Answer: A · Drug reaction with eosinophilia and systemic symptoms
DRESS typically starts 2-8 weeks after a drug such as an aromatic anticonvulsant, allopurinol or dapsone is begun. Fever, facial oedema, a widespread rash, lymphadenopathy, eosinophilia and organ involvement (most often the liver) are the hallmarks. The drug must be stopped, and systemic steroids are usually needed; phenytoin and phenobarbital may cross-react and should be avoided. Relapse can occur weeks later as steroids are tapered.
- B: SJS causes mucosal erosions and epidermal detachment, which are absent here.
- C: AGEP starts within days with sheets of sterile pustules and neutrophilia.
- D: Fixed drug eruption gives one or a few dusky patches that recur at the same site.
Question 2 · Easy
A 45-year-old woman has flaccid blisters and raw erosions on her trunk. When the resident applies firm sliding pressure with a finger on normal-looking skin next to a lesion, the upper epidermis shears off. What does this positive sign indicate?
1. AA split at the basement membrane zone
2. BMast cell degranulation in the dermis
3. CLoss of cohesion within the epidermis
4. DFragility of dermal blood vessels
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Answer: C · Loss of cohesion within the epidermis
This is the Nikolsky sign: sliding pressure separates the upper epidermis from the layers below in apparently normal skin. It indicates weak cohesion within the epidermis, as in pemphigus (acantholysis from antibodies to desmogleins), and it is also positive in TEN and staphylococcal scalded skin syndrome. It is typically negative in bullous pemphigoid, where the split is subepidermal and the overlying epidermis is intact. The sign helps at the bedside, but biopsy and immunofluorescence confirm the diagnosis.
- A: Subepidermal splits, as in pemphigoid, give tense blisters and a negative Nikolsky sign.
- B: Mast cell degranulation on rubbing is the Darier sign of mastocytosis.
- D: Vascular fragility gives purpura, not shearing of the epidermis.
Question 3 · Medium
A 50-year-old farmer has had superficial, crusted, scaly erosions on his face, scalp, upper chest and back for 6 months, looking like cornflakes. Intact blisters are rarely seen, and his oral mucosa is completely normal. Biopsy shows a split high in the epidermis, at the granular layer. Antibodies against which antigen are most likely present?
1. ABP180 (collagen XVII)
2. BDesmoglein 3
3. CDesmoglein 1
4. DType VII collagen
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Answer: C · Desmoglein 1
Superficial crusted erosions in a seborrhoeic distribution with no mucosal involvement and a split at the granular layer is pemphigus foliaceus, caused by IgG against desmoglein 1. Desmoglein 1 is concentrated in the upper epidermis, while mucosa relies mainly on desmoglein 3, which compensates there, so the mouth is spared. Pemphigus vulgaris, in contrast, has antibodies to desmoglein 3 (with or without desmoglein 1) and usually starts in the mouth.
- A: BP180 antibodies cause bullous pemphigoid, with tense subepidermal blisters.
- B: Desmoglein 3 antibodies cause pemphigus vulgaris, with oral erosions and a suprabasal split.
- D: Type VII collagen antibodies cause epidermolysis bullosa acquisita, with a deep subepidermal split.
Question 4 · Hard
A 58-year-old man with chronic lymphocytic leukaemia has had severe, painful erosions of the lips, tongue and buccal mucosa for 2 months that have not responded to oral steroids, with bilateral conjunctivitis. His skin shows a mix of flaccid blisters, target-like lesions and lichenoid papules, including on the palms. Which test best supports the most likely diagnosis?
1. AIndirect immunofluorescence on salt-split skin
2. BTzanck smear for multinucleated giant cells
3. CSerum anti-tissue transglutaminase IgA
4. DIndirect immunofluorescence on rat bladder epithelium
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Answer: D · Indirect immunofluorescence on rat bladder epithelium
Intractable, severe stomatitis with polymorphous skin lesions (blisters, targets and lichenoid lesions, including on the palms) in a patient with a lymphoproliferative disorder is paraneoplastic pemphigus. Patients have antibodies to desmogleins and also to plakin proteins such as envoplakin and periplakin, which are present in transitional epithelium; staining of rat bladder epithelium on indirect immunofluorescence is therefore a specific supporting test, as pemphigus vulgaris serum does not stain it. The underlying neoplasm is treated, and bronchiolitis obliterans is a feared, often fatal complication.
- A: Salt-split skin separates pemphigoid from epidermolysis bullosa acquisita, both subepidermal.
- B: Multinucleated giant cells indicate herpes infection, not an autoimmune blistering disease.
- C: Anti-tTG IgA supports coeliac disease and dermatitis herpetiformis.
Question 5 · Medium
A 25-year-old woman is admitted with toxic epidermal necrolysis involving 40% of her body surface area, 10 days after starting co-trimoxazole for a urinary infection. She is haemodynamically stable. What is the most appropriate initial management?
1. ARoutine prophylactic broad-spectrum IV antibiotics
2. BContinue co-trimoxazole with IV steroid cover
3. CStop co-trimoxazole and give burns-unit supportive care
4. DSilver sulfadiazine dressings to all raw areas
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Answer: C · Stop co-trimoxazole and give burns-unit supportive care
The single most important step in SJS/TEN is to stop the culprit drug at once, since early withdrawal improves survival. Care is supportive, ideally in a burns unit or ICU: warm environment, fluid and electrolyte balance, nutrition, non-adherent dressings, eye and mucosal care, pain relief and close watch for infection. Silver sulfadiazine is avoided because it is a sulphonamide like co-trimoxazole, and systemic antibiotics are given only for suspected or proven infection, not as prophylaxis.
- A: Prophylactic antibiotics select resistant organisms and are given only for infection.
- B: The culprit drug must be stopped; steroids do not make it safe to continue.
- D: Silver sulfadiazine is a sulphonamide and could re-expose her to the culprit class.
Question 6 · Hard
A 76-year-old woman with type 2 diabetes has taken metformin and vildagliptin for 14 months. For 2 months she has had intensely itchy urticarial plaques, and over the last 2 weeks large tense blisters with clear fluid have appeared on her thighs, groins and lower abdomen. Her mouth is spared and the Nikolsky sign is negative. Biopsy shows a subepidermal blister rich in eosinophils. Besides treating the skin, what is the most appropriate change in her management?
1. AStop metformin and switch to a sulfonylurea
2. BAdd oral acyclovir for viral reactivation
3. CStop vildagliptin and adjust diabetes therapy
4. DContinue both drugs and add oral prednisolone
Answer and explanation in LearnFree account
Question 7 · Medium
A 27-year-old woman in her second pregnancy at 28 weeks has intensely itchy urticarial plaques that began around the umbilicus and have spread to the trunk and thighs; over the past few days tense blisters have appeared on the plaques. Liver function tests and serum bile acids are normal. Direct immunofluorescence of perilesional skin shows linear C3 along the basement membrane zone. What is the most likely diagnosis?
1. APemphigoid gestationis
2. BAtopic eruption of pregnancy
3. CIntrahepatic cholestasis of pregnancy
4. DPolymorphic eruption of pregnancy
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Question 8 · Easy
A 27-year-old man from Lucknow has a round, dusky violet, slightly swollen, burning patch on the glans penis. The same patch has appeared at the same spot three times in the past year, each time a day after he took tablets for loose motions, and each time it faded leaving a dark mark. What is the most likely diagnosis?
1. AFixed drug eruption
2. BRecurrent genital herpes
3. CLichen planus
4. DErythema multiforme
Answer and explanation in LearnFree account
Question 9 · Hard
A 24-year-old man was started on phenytoin after a seizure following a head injury. Five weeks later he has fever of 39.5°C, facial swelling, a widespread morbilliform rash, generalised lymphadenopathy, eosinophils 3,100/µL, atypical lymphocytes and ALT 380 U/L. Phenytoin is stopped and systemic steroids are started. His neurologist wants him on an antiepileptic for some months more. Which drug is the safest choice?
1. APhenobarbitone
2. BLevetiracetam
3. CCarbamazepine
4. DOxcarbazepine
Answer and explanation in LearnFree account
Question 10 · Medium
A 34-year-old man developed fever, sore red eyes and painful erosions of the lips, mouth and genitals 2 weeks after starting a new drug. Dusky purpuric macules and flat atypical targets on his trunk have blistered, and the detached plus detachable epidermis is estimated at 20% of his body surface area. Which diagnosis best fits?
1. AToxic epidermal necrolysis
2. BErythema multiforme major
3. CStevens-Johnson syndrome
4. DSJS/TEN overlap
Answer and explanation in LearnFree account
Question 11 · Medium
A 46-year-old woman was started on amoxicillin for sinusitis. Two days later she has fever of 38.8°C and widespread red, oedematous skin, most marked in the axillae and groins, studded with hundreds of tiny non-follicular pustules. Neutrophils are 13,000/µL. She has no past skin disease, and her mucosae are spared. What is the most likely diagnosis?
1. AGeneralised pustular psoriasis
2. BDrug reaction with eosinophilia and systemic symptoms
3. CAcute generalised exanthematous pustulosis
4. DToxic epidermal necrolysis
Answer and explanation in LearnFree account
Question 12 · Medium
A 22-year-old college student has had four episodes in 18 months of round, raised target lesions with three concentric zones on her palms, backs of hands and forearms, with a few lip erosions. Each episode follows a cold sore by about a week and clears in 2-3 weeks. What will best prevent further episodes?
1. AContinuous oral acyclovir for months
2. BAvoiding all non-essential drugs
3. COral antihistamines at each episode
4. DA short course of oral prednisolone
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Question 13 · Medium
A 61-year-old man from Hyderabad is admitted with fever, conjunctivitis, lip and oral erosions and blistering dusky macules on his trunk. He has taken amlodipine and atorvastatin for 6 years and occasional paracetamol for headache. Three weeks ago a private doctor started allopurinol 300 mg daily for a serum uric acid of 8.4 mg/dL found on a health check, though he has never had gout. Which drug is most likely responsible?
1. AAmlodipine
2. BAllopurinol
3. CParacetamol
4. DAtorvastatin
Answer and explanation in LearnFree account
Question 14 · Medium
A dermatology postgraduate is examining a 72-year-old man admitted with a blistering eruption and lists four findings that would favour bullous pemphigoid over pemphigus vulgaris: 1. Tense blisters that stay intact for days 2. Erosions of the buccal mucosa as the first sign 3. Eosinophils in a subepidermal blister on biopsy 4. Linear IgG and C3 along the basement membrane zone on direct immunofluorescence. Which findings truly favour bullous pemphigoid?
1. A2 and 3 only
2. B1, 2 and 4 only
3. C1, 3 and 4 only
4. D3 and 4 only
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Question 15 · Easy
A 30-year-old man has intensely itchy, grouped small vesicles and excoriations symmetrically over the elbows, knees and buttocks. He also has intermittent loose stools and mild iron deficiency. Which finding on direct immunofluorescence of perilesional skin is expected?
1. AIntercellular IgG in a net-like pattern
2. BLinear IgG and C3 along the basement membrane
3. CGranular IgA in the dermal papillae
4. DLinear IgA along the basement membrane
Answer and explanation in LearnFree account
Question 16 · Medium
A 30-year-old man started on multibacillary MDT for leprosy 5 weeks ago now has fever, facial oedema, a generalised exfoliating rash, tender lymph nodes, eosinophils of 2,400/µL and ALT 420 U/L. Dapsone is suspected. Reactivation of which virus is characteristically linked to this type of reaction and its relapses?
1. AHuman herpesvirus 6
2. BVaricella-zoster virus
3. CParvovirus B19
4. DHerpes simplex virus 1
Answer and explanation in LearnFree account
Question 17 · Hard
A 52-year-old man is admitted to the ICU with toxic epidermal necrolysis from carbamazepine. He has no history of cancer. On day 1: pulse 126/min, epidermal detachment 35% of body surface area, blood urea 12 mmol/L, serum bicarbonate 22 mmol/L and blood glucose 9 mmol/L (162 mg/dL). What is his SCORTEN score?
1. ASCORTEN 3
2. BSCORTEN 4
3. CSCORTEN 5
4. DSCORTEN 2
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Question 18 · Medium
A 19-year-old woman is recovering in the ward from Stevens-Johnson syndrome caused by an anticonvulsant; her skin erosions have healed over 3 weeks. Her mother asks what problem is most likely to trouble her in the long term. Which complication is most common in survivors?
1. AChronic ocular surface disease
2. BHypertrophic skin scarring
3. CChronic liver disease
4. DChronic kidney disease
Answer and explanation in LearnFree account
Question 19 · Easy
A 38-year-old man has had painful oral erosions for 2 months and now has flaccid blisters on his chest. A Tzanck smear is made from the floor of a fresh blister. Which finding would support pemphigus vulgaris?
1. AMany eosinophils without epithelial cells
2. BClusters of Gram-positive cocci
3. CRounded acantholytic keratinocytes
4. DMultinucleated giant cells with moulding
Answer and explanation in LearnFree account
Question 20 · Medium
A 42-year-old woman from Kolkata has had painful oral erosions for 3 months and now has flaccid blisters and widespread erosions on her scalp, chest and back. The Nikolsky sign is positive. Biopsy shows suprabasal acantholysis, and direct immunofluorescence shows intercellular IgG. Which treatment is first-line for her?
1. ADoxycycline with nicotinamide
2. BTopical clobetasol alone
3. COral dapsone alone
4. DSystemic corticosteroids with rituximab
Answer and explanation in LearnFree account

Bullous disorders and drug reactions

A 45-year-old woman has flaccid blisters and raw erosions on her trunk. When the resident applies firm sliding pressure with a finger on normal-looking skin next to a lesion, the upper epidermis shears off. What does this positive sign indicate?

A 25-year-old woman is admitted with toxic epidermal necrolysis involving 40% of her body surface area, 10 days after starting co-trimoxazole for a urinary infection. She is haemodynamically stable. What is the most appropriate initial management?

A 30-year-old man has intensely itchy, grouped small vesicles and excoriations symmetrically over the elbows, knees and buttocks. He also has intermittent loose stools and mild iron deficiency. Which finding on direct immunofluorescence of perilesional skin is expected?

A 19-year-old woman is recovering in the ward from Stevens-Johnson syndrome caused by an anticonvulsant; her skin erosions have healed over 3 weeks. Her mother asks what problem is most likely to trouble her in the long term. Which complication is most common in survivors?

A 38-year-old man has had painful oral erosions for 2 months and now has flaccid blisters on his chest. A Tzanck smear is made from the floor of a fresh blister. Which finding would support pemphigus vulgaris?