Increased plasma histamine level in eosinophilic fasciitis.

In a patient with eosinophilic fasciitis, a biopsy specimen obtained within 4 weeks of the onset of symptoms showed infiltration of the subcutis and fascia with mast cells, and there was up to a 19-fold increase in plasma histamine levels. The patient improved and experienced softening of the skin when treated with systemic corticosteroids and a histamine2-receptor antagonist, and her plasma histamine level returned to normal. Tissue mast cell infiltration and excessive plasma histamine levels were not present in two otherwise similar patients with eosinophilic fasciitis who were studied 7 months after disease onset. It is possible that mast cells play a pathogenic role in some patients with eosinophilic fasciitis.