What is psoriasis?
Psoriasis is a common chronic skin condition characterised by symmetrically distributed, well-defined scaly plaques. The most common type of psoriasis is chronic plaque psoriasis, which often starts in early adult life.
What is drug-induced psoriasis?
In some people, psoriasis is drug-induced or drug-aggravated.
- In drug-induced psoriasis, discontinuation of the offending drug leads to the clearance of the psoriasis. It occurs in patients with no previous history of psoriasis.
- In drug-aggravated psoriasis, the disease continues to develop even after the causative drug has been discontinued. It typically occurs in patients with a personal or family history of psoriasis.
These forms of psoriasis differ from psoriasiform drug eruption, a group of papular drug eruptions characterised histologically by epidermal hyperplasia and hypergranulosis.
Who gets drug-induced psoriasis?
As with psoriasis that is not induced by a drug, drug-induced psoriasis occurs more frequently in patients with a history of:
Other risk factors for psoriasis include:
- Race — psoriasis occurs in all races, but it is more common in Caucasians than in those of African descent
- A family history of psoriasis
- Age — the most common ages for the onset of psoriasis are 16–22 years and 57–60 years.
What causes drug-induced psoriasis?
The most common drugs to induce or aggravate psoriasis are:
- Antimalarial drugs (eg, hydroxychloroquine)
- Non-steroidal anti-inflammatory drugs (NSAIDs)
- Angiotensin-converting enzyme (ACE) inhibitors.
What are the clinical features of drug-induced psoriasis?
Drug-induced or drug-aggravated psoriasis may induce:
- Localised plaque psoriasis, often affecting scalp, knees, elbows, buttocks and/or genitals
- Generalised plaque psoriasis, with scattered plaques on all parts of the body
- Erythroderma when the entire skin surface is red and scaly.
Palmoplantar pustulosis can also be drug-induced, often by tumour necrosis factor inhibitors. Although closely related, palmoplantar pustulosis is no longer classified as a type of psoriasis. It nearly always occurs in smokers.
How is drug-induced psoriasis diagnosed?
Diagnosis of drug-induced psoriasis can be challenging when patients are on multiple medications. The onset of psoriatic symptoms can be months or years after the drug has been started. A careful patient history is essential in any patient that presents with new-onset psoriasis and must include their current medications. The possibility of other triggers for the psoriasis, apart from drugs, should also be taken into consideration.
How is drug-induced psoriasis treated?
The standard of care in the case of drug-induced psoriasis is to discontinue the offending drug. However, this is not always possible; for example, in a patient with severe depression that is well controlled by lithium where other options have been ineffective or contraindicated.
Treatments for psoriasis include:
- Topical corticosteroids
- Vitamin D analogues such as calcipotriol
- Immune modulators such as methotrexate, ciclosporin, mycophenolate
What is the outcome for drug-induced psoriasis?
While some cases of drug-induced psoriasis can resolve within weeks of stopping the causative medicine, in other cases, it can take much longer to resolve or not resolve completely.