Bullous Reactions/ Fixed Drug Eruptions/ Coma Bullae

What broad categories can drug-related bullous reactions mimic?

Pemphigus vulgaris; pemphigus foliaceus; bullous pemphigoid

Which blister level is seen in pemphigus foliaceus?

Below/within granular layer

Which blister level is seen in pemphigus vulgaris?

Suprabasal

Which drugs with thiol groups classically cause pemphigus-like disease?

Penicillamine; captopril

Which drugs can cause bullous pemphigoid-like tense bullae?

Furosemide; penicillin; sulfasalazine

What test shows immunoglobulin deposition in drug-induced autoimmune blistering?

Direct immunofluorescence

How long can bullous drug reactions persist after the drug is stopped?

Up to 6 months

What beetle-derived topical vesicant is used therapeutically?

Cantharidin

What is a fixed drug eruption?

Well-circumscribed erythematous to dusky patch/plaque that recurs at same site on reexposure

When does fixed drug eruption usually appear after first exposure?

~1 to 2 weeks

When does it recur after reexposure?

Often within 24 hours

Common sites of fixed drug eruption?

Acral extremities; genitals; intertriginous sites

Does fixed drug eruption heal completely normal?

No; residual hyperpigmentation common

Can generalized fixed drug eruption mimic TEN?

Yes

Classic drugs causing fixed drug eruption?

Acetaminophen; allopurinol; barbiturates; captopril; carbamazepine; erythromycin; metronidazole; minocycline; naproxen; NSAIDs; salicylates

What are coma bullae?

Tense bullae on normal-appearing skin in comatose patients

When do coma bullae usually appear?

Within 48 to 72 hours

Which overdose is classically associated with coma bullae?

Phenobarbital/sedative-hypnotics

What toxic gas is another classic cause of coma bullae?

Carbon monoxide

Main proposed mechanism of coma bullae?

Pressure-induced epidermal necrosis

What eccrine finding is seen histologically in coma bullae?

Eccrine duct and gland necrosis