Sequential clinico-histological studies in psoriasis following methotrexate therapy

Ten cases of psoriasis were studied to see the pattern of histological resolution and to evaluate clinico-histological correlation in psoriasis following weekly methotrexate therapy. Five sequential biopsies were taken in each patient. Scaling was first to regress followed by induration and erythema in 18, 26 and 35 days, respectively. Uniform granular layer appeared in 4 days, stratum corneum became orthokeratotic in 7 days, mitotic activity got restricted to basal layer in 7 days and rete ridges elongation was reduced to half in 11 days. Mild acanthosis, cellular infiltrate and vascular dilatation persisted even after full clinical regression. Interestingly, 5 out of 10 biopsies revealed increase in cellular infiltrate and oedema after first methotrexate pulse.