AN EXPERIMENTAL-MODEL OF FASCIITIS-PANNICULITIS - INDUCTION OF CHRONIC FIBROSING PANNICULITIS IN THE RAT BY SUBCUTANEOUS INJECTIONS OF LIPASE

We describe an experimental model of the fasciitis-panniculitis syndro me, which includes eosinophilic fasciitis and its related disorders. R ats were given a single or repeated subcutaneous injections of saline or a 10% lipase solution. The injection sites were studied histologica lly and histomorphometrically. With few exceptions, the subcutaneous-f ascial unit of the saline-injected rats was normal. An acute necrotizi ng panniculitis with inflammatory involvement of the adjacent fascia w as found 2 days after a single injection of lipase. Three to 6 weeks a fter a single injection of lipase, the subcutaneous fat tissue and fas cia were fibrotically thickened and chronically inflamed. Similar but more advanced alterations had developed in animals killed 3 weeks afte r three weekly injections of lipase. Progressive fibrotic thickening o f the subcutaneous-fascial unit was observed following an increasing n umber of weekly lipase injections. The acute-phase reaction expresses a pattern of steatonecrotic tissue damage. In the chronic phase, the f ibrotically thickened subcutaneous layers typify a reaction pattern an alogous to that of the human fasciitis-panniculitis syndrome. This exp erimental model permits better appreciation of the disorder's nonspeci fic pathogenesis and may help in the search for alternative therapeuti c modalities.