We present an extremely serious clinical case of Stevens-Johnson syndrome, the evolution of which has been followed for 3 years. The etiology was unknown, although it was related with the administration of amoxicillin. We found a type III immunity mechanism involving immune complexes. The serious complications affected the skin, mucosae and internal organs. The present sequelae are: esophageal stenosis, pneumopathy with a 50% deficit of pulmonary perfusion and bilateral trichiasis.