Abnormalities of serum type III procollagen aminoterminal peptide in methotrexate-treated psoriatic patients with normal liver histology do not correlate with hepatic ultrastructural changes.

In a previous study, it was shown that the serum levels of type III procollagen aminoterminal peptide (P3NP) were significantly greater in patients receiving methotrexate (MTX) treatment for psoriasis than in untreated control patients with psoriasis. Although levels were highest in patients with hepatic fibrosis and cirrhosis, serum P3NP concentrations in those patients with normal liver histology on light microscopy were also shown to be significantly higher than in controls. In the present study, liver biopsies from 22 such 'normal' patients were examined by electron microscopy, in order to determine whether P3NP levels correlated with ultrastructurally demonstrable fibrosis. Fibrosis in the perisinusoidal space of Disse was present in as many as 82% of biopsies. Although the prevalence of such fibrosis in psoriasis patients who have not received MTX is unknown, the high prevalence of Disse space fibrosis and of raised P3NP in MTX-treated patients suggests that MTX causes subtle liver damage in a majority of treated patients. However, we were unable to show a statistical correlation between P3NP and the degree of Disse space fibrosis.