Erythroderma is an erythema in more than 90% of the body surface and represents a dermatological emergency with extensive erythematous skin and scaling. First described by Von Hebra in 1868, erythroderma represents a rare cutaneous inflammatory state with associated dysfunction of both the skin barrier and metabolic processes. Most cases result from pre-existing and chronic dermatoses such as eczema and psoriasis. Untreated, the patient may succumb to multisystem organ failure and high-output heart failure secondary to cutaneous volume loss. We present a case of Exfoliative Psoriatic Erythroderma as a patient’s first presentation of psoriasis in the eighth decade of life, with no dermatological history, who started with erythrodermic psoriasis, developing a systemic inflammatory response, which was treated with methotrexate with good response. Erythrodermic psoriasis is a severe and rare variant of psoriasis vulgaris, the condition of which can be fatal. The objective of presenting this case is to call attention to this rare entity.