Toxic oil syndrome. A long-term follow-up of a cohort of 332 patients.

Toxic oil syndrome is a multisystemic, epidemic disease that appeared in Spain in 1981, related to the intake of rapeseed cooking oil sold in bulk. It affected 19,748 people, of whom 457 died. The toxic substance was never identified. We report the 8-year follow-up of a cohort of 332 patients. The disease was usually severe and disabling during the first 2 years, but the clinical condition of most of the patients improved thereafter. The acute phase lasted 2 months, and was characterized by pulmonary edema, rash, eosinophilia, and myalgia. During the intermediate phase (second to fourth months), severe myalgia, skin tenderness, subcutaneous edema, altered liver function, and pulmonary hypertension developed. Later on, an early chronic phase developed, from the fourth month to the end of the second year. It was marked by scleroderma, sicca syndrome, polyneuropathy, joint contractures, weight loss, and functional limitations. The clinical manifestations improved during the late chronic phase. Its most prominent clinical features were muscle cramps, chronic musculoskeletal pain, chronic lung disease, Raynaud phenomenon, carpal tunnel syndrome, and psychologic disturbances. Only 9% of the patients achieved remission after the acute phase, the rest developing late clinical manifestations of the disease. The severity of the chronic manifestations was rather variable. At the end of the 8-year follow-up, there were 10 TOS-related deaths (3%), 47% of the patients had some kind of complaint, albeit subtle in most cases, and 16% showed organic involvement related to TOS. The most important pathologic features of TOS were widespread interstitial infiltrates, non-necrotizing angiitis, endothelial proliferation, and tissue fibrosis. Toxic oil syndrome is a dramatic example of an induced scleroderma-like syndrome, similar to the eosinophilia-myalgia syndrome. Patients with EMS may develop some of the late clinical features of TOS in the years to come.