Azathioprine is employed for its immunosuppressive properties, as a
steroid-sparing agent or as monotherapy. Its most traditional clinical indications are
connective tissue diseases,
vasculitis, post-transplant, and immunobullous
dermatoses. The main disadvantages of
azathioprine therapy are a delayed onset of action (6-8 weeks), and rare profound bone marrow toxicity. Susceptibility to bone marrow toxicity is due to a genetically determined metabolic defect (1 in 300). Patients at risk of such toxicity may be identified by a
Thiopurine methyltransferase enzyme assay. We have undertaken a retrospective study, looking at the use of
azathioprine as monotherapy for non-bullous inflammatory
dermatoses. We studied a total of 24 patients (10 male, 14 female). The
dermatoses comprised:
atopic eczema (10),
pompholyx (6), plaque
psoriasis (6), and
chronic actinic dermatitis (2). All patients had severe refractory disease warranting systemic second line
therapy. The mean age was 49.4 years (range 17-86 years). The starting dose of
azathioprine was 100-150 mg/day, and the maintenance dose 50-100 mg/day. The mean
duration of treatment was 33.5 months(range 1-132 months). Eighteen patients (75%) showed a good to excellent sustained clinical response to
azathioprine. This response rate was evenly represented in the 4
dermatoses studied. The adverse reactions encountered were raised MCV (6), leucopenia (2), raised hepatic
enzymes (6), and
dyspepsia (4).
Azathioprine had to be discontinued due to adverse reactions in 2 patients (
dyspepsia, raised hepatic
enzymes) followed by normalization. Other factors that potentially contributed to the observed adverse events were present in 5 patients:
alcoholism (2),
erythromycin toxicity (1), and malabsorption (2). Our study demonstrates the efficacy of
azathioprine monotherapy for severe
atopic eczema,
pompholyx, plaque
psoriasis, and
chronic actinic dermatitis. Furthermore,
azathioprine is a low cost and generally well tolerated
drug.