Fixed drug reactions, are common and indicating they recur at the same site with each exposure to a particular medication.
Medications inducing fixed drug eruptions are usually those taken intermittently.
Accounts for up to 39% of all drug eruptions.
Is most common in adults, particularly from ages 40-80 years.
Signs and symptoms include: painful and itchy reddish/purple patch of skin that occurs in the same location with repeated exposures to the culprit drug is the classic presentation of a fixed drug reaction.
The lips, genitals, and hands are often involved.
Sensitization usually occurs a few weeks after the initial medication exposure.
Rarely, the process can occur over the course of several years, as in the case of sporadic use of drugs.
The reason for recurrence of lesions in the exact anatomical site has not been explained: it is thought the fixed eruption is a cytotoxic T-cell-mediated immune reaction and that skin resident effective/memory T cells are the key mediators.
Fixed drug eruption ends with activated cytotoxic T cells being removed by apoptosis, but a small population of such cells survive.
The remaining population of skin resident T cells in the lesional site forms a fixed drug irruption lesion.
When the re-exposure of a drug antigen occurs, there is activation and expansion of these residual T cells and the recurrent fixed drug eruption develops, usually within 30 minutes-eight hours after intake of the drug.
Histopathology shows epidermal immigration of lymphocytes, apoptotic keratinocytes, degeneration of basal keratinocytes leading to sub epidermal blistering.
The histopathology features resemble that of erythema multiforme or Stevens-Johnson syndrome.
To confirm the diagnosis and oral provocation test with the implicated drug is performed.
Medications that are commonly implicated as a cause of fixed drug eruptions include the following:
The majority of such drug eruptions are self limiting.
Topical steroids are used to reduce symptoms and systemic steroids may be necessary in patients with multiple lesions.
A severe generalized bullous fixed drug irruption is treated in an ICU setting, similar to Stevens-Johnson syndrome and toxic epidermal necrolysis.