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Patient Case: Drug Eruption

Patient Case: Drug Eruption

Discussion

A 45-year-old man presents to the dermatology clinic with a widespread red rash that started five days ago. He reports that the rash began on his trunk as small, red macules, which then spread to his arms, legs, and neck. The lesions are slightly itchy but not painful. He denies fever, joint pain, or mucosal involvement.

Upon further questioning, he mentions that he was recently prescribed amoxicillin for a sinus infection and started taking it seven days ago. He has no history of allergies and has never experienced a similar reaction before.

On examination, there are multiple erythematous maculopapular lesions symmetrically distributed on the trunk and extremities, with no blistering or desquamation. There is no facial swelling, mucosal involvement, or systemic symptoms.

A diagnosis of a morbilliform (exanthematous) drug eruption is made. The patient is advised to discontinue amoxicillin immediately, take oral antihistamines for itching, and use topical corticosteroids for inflammation. He is also educated on the importance of informing healthcare providers about this reaction in the future to prevent recurrence.

Questions
  1. What is the most likely diagnosis for this patient’s condition?
    a) Urticaria
    b) Erythema multiforme
    c) Drug-induced morbilliform eruption
    d) Contact dermatitis
  2. What is the most likely cause of this patient’s drug eruption?
    a) Ibuprofen
    b) Amoxicillin
    c) Metformin
    d) Propranolol
  3. Which of the following clinical features suggests a simple morbilliform drug eruption rather than a severe drug reaction?
    a) Mucosal involvement and blistering
    b) Symmetric erythematous maculopapular rash without systemic symptoms
    c) Skin necrosis and epidermal detachment
    d) Facial swelling and eosinophilia
  4. What is the best initial management for this condition?
    a) Continue the medication and monitor for progression
    b) Immediately discontinue the suspected drug and start antihistamines
    c) Administer systemic corticosteroids in all cases
    d) Perform a skin biopsy for confirmation before stopping the drug
Reveal answers

Answers

  1. (c) Drug-induced morbilliform eruption
    • The symmetrically distributed maculopapular rash that appeared a few days after starting amoxicillin suggests a morbilliform (exanthematous) drug eruption, the most common type of drug reaction.
  2. (b) Amoxicillin
    • Beta-lactam antibiotics (e.g., amoxicillin, penicillin) are common causes of morbilliform drug eruptions, especially in patients with viral infections like Epstein-Barr virus (EBV).
  3. (b) Symmetric erythematous maculopapular rash without systemic symptoms
    • A mild drug eruption is characterized by a blanching, erythematous rash without systemic symptoms. Severe reactions like Stevens-Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN) involve mucosal lesions, blisters, and necrosis.
  4. (b) Immediately discontinue the suspected drug and start antihistamines
    • Stopping the offending medication is the first step. Antihistamines and topical corticosteroids help relieve itching and inflammation. Systemic corticosteroids are generally reserved for more severe reactions.