A 23-year-old with a severe rash

There is a patchy and confluent erythematous rash studded with fine pseudo pustules and peripheral circular peeling seen over the abdomen. 

The likely cause is lamotrigine-induced generalised pustular psoriasis (GPP). Lamotrigine is a widely used antiepileptic commonly producing cutaneous side effects (incidence 10%). However, this is the first report of lamotrigine-induced GPP. 

Other differential diagnoses would include:

• Acute generalised exanthematous pustulosis — this typically starts within days of drug introduction and is known to resolve within 15 days (in contrast to GPP which takes months to resolve) with drug discontinuation.
• Subacute lupus erythematosus — this is often drug-induced, producing annular scaly lesions over the trunk
• Pemphigus foliaceous — blisters are seldom seen as they occur superficially and burst easily; IMF would also be positive.

After stopping the offending drug (lamotrigine in this case), the first-line treatment for generalised pustular psoriasis (GPP) would include acitretin, ciclosporin, or methotrexate. If this is insufficient, a biologic agent could be considered. 

It is important to note that glucocorticosteroids typically flare pustular psoriasis, particularly on withdrawal, so are contraindicated for GPP.