Abstract： To report a case of retinoic acid syndrome due to tretinoin in the treatment of psoriasis.A 32-year-old male patient presented with psoriasis vulgaris for more than 10 years.In recent 10 years,he experienced erythema,plaques covered with multi-layered scales on the scalp,trunk,extremities accompanied by pruritus.The patient was diagnosed as psoriasis and given long-term treatment with oral vitamins,traditional Chinese medicine,and topical drugs,which resulted in a status of remission and exacerbation.Half a year prior to the presentation,the patient was given acitretin 10 mg twice daily due to the exacerbation of condition;20 days later,the dose increased to thrice daily;after another 30 days,the lesions were improved,and the frequency decreased to twice daily again;finally,a disappearance of the lesions was achieved after half a year of maintenance treatment with acitretin 10 mg twice daily.One week prior to the presentation,the treatment strategy was altered from acitretin to viaminate 50 mg twice daily;after three days with viaminate,the patient experienced a sudden worsening of psoriatic lesions with an obvious inflammatory reaction;subsequently,the lesions rapidly spread to the whole body surface and fused into large patches,accompanied with the following signs:marked edema,massive desquamating,high fever (＞39℃),hypotension,respiratory distress,pulmonary edema,pleural and pericardial effusions,renal dysfunction,peripheral blood leukocytosis.The patient was diagnosed as retinoic acid syndrome(RAS).After given oral glucocorticoid,symptomatic and supportive treatment,he experienced a relief of symptoms.These findings indicate that RAS is an entity with an abrupt onset and poor prognosis.For patients with RAS,early diagnosis and prompt management with corticosteroids,symptomatic and supportive treatments are essential to avoid potential fatal complications.