Fixed drug eruption

Question 1

Most common causes of fixed drug eruption:

Answer 1

1. sulfonamides (75% of cases)
   - NSAIDS (especially Naproxen)
   - TCNs
   - Phenolphthalein (previously in laxatives)
   - Pseudoephedrine (classic cause)

Question 2

1 cause of fixed drug eruption on the genitalia:

Answer 2

• sulfonamides

Question 3

fixed drug eruption caused by NSAIDs has a prediliction for which body site?

Answer 3

• lips

Question 4

fixed drug eruption most common sites of presentation?

Answer 4

• oral and genital mucosa are # 1 sites
• face, hands/feet

Question 5

Initial episode of fixed drug eruption occurs how long after initiation of causative drug?

Answer 5

• 1-2 weeks

Question 6

Subsequent episodes of fixed drug eruption occurs at the same site as initial, but within how long of drug administration?

Answer 6

• 30 mins to 8 hours (as opposed to 1-2 weeks for initial presentation)

Question 7

If drugs causing fixed drug eruption are continued it may lead to generalized FDE which can be difficult to distinguish from _______

Answer 7

• EM or SJS

Question 8

Appearance of lesions of fixed drug eruption:

Answer 8

• well-demarcated, edematous plaques w/ erythematous-violaceous hue

Question 9

Epidermal damage from interface of fixed drug eruption often leads to central _______

Answer 9

• dusky hue, bulla, or erosion

Question 10

lesions of fixed drug eruption take how long to resolve?

Answer 10

• 1-2 weeks (same as initial onset)

Question 11

fixed drug eruption often heals with _______

Answer 11

prominent postinflammatory hyperpigmentation

Question 12

Non-pigmenting fixed drug eruption is most commonly due to which medication?

Answer 12

• pseudoephedrine

Question 13

Histopathology of fixed drug eruption:

Answer 13

• EM-like vacuolar interface changes
• scattered apoptotic keratinocytes in all layers of epidermis

- superficial to mid dermal perivascular lymphohistiocytic infiltrate w/ admixed eosinophils and neutrophils

- increased dermal melanophages within papillary and reticular dermis

Question 14

What testing can be done to help identify culprit medication in fixed drug eruption?

Answer 14

• Patch testing within site of prior involvement

Question 15

Prognosis/clinical course of fixed drug eruption:

Answer 15

• benign (unless generalized bullous FDE)
• self resolves in days to a few weeks if causative med is discontinued