Psoriasis Case 6: Erythrodermic psoriasis

A 29-year-old man with a family history of psoriasis presented for evaluation of a severe flare of his pre-existing psoriasis. The patient developed plaque type psoriasis at 12 years of age, and was initially treated with low-potency topical corticosteroids. His disease became progressively worse over the subsequent 6 years with the development of extensive plaques involving his scalp, trunk, and extremities. He was treated initially with 15 mg per week of oral MTX that unfortunately led to significant elevations in his LFT findings after 9 months of therapy, requiring discontinuation of MTX. Subsequently, he failed to respond to a 12-week course of intramuscular alefacept, but thereafter obtained significant improvement with etanercept treatment. Nine months before his presentation, he left the United States to join his family in Mexico and failed to renew his etanercept. Approximately 7 months after his last dose of etanercept, he noticed an increased number of new psoriatic plaques. Thereafter, an upper respiratory infection led to a rapid worsening of his psoriasis, and eventual involvement of most of his BSA with sparing only of the palms and soles. His psoriasis was painful, and he developed frequent chills, leg swelling, and generalized arthralgias. The patient did not smoke or drink alcohol and denied exposure to toxic chemicals. 

On physical examination, the patient was afebrile with other vital signs within normal limits. He had generalized erythematous, inflammatory patches and plaques covering 95% of his BSA. Superficial exfoliation of the face, palms, and soles were noted, along with pitting edema of the lower extremities. Joint examination revealed swelling of the toes without any specific individual joint tenderness.


Severe flares of psoriasis can be induced by multiple factors including stress, systemic infections, and medications. The most severe form of psoriasis, erythrodermic psoriasis, may closely resemble other forms of erythroderma including atopic dermatitis, contact dermatitis, seborrheic dermatitis, cutaneous T-cell lymphoma, and pityriasis rubra pilaris, both clinically and histologically. Often, the diagnosis is made by the patient’s history and subtle clues in the clinical presentation with skin biopsy specimens aiding in the diagnosis in selected cases.

In this patient, the personal and family history of psoriasis strongly favors the diagnosis of erythrodermic psoriasis. In addition, he had areas of indurated plaques and associated silvery scale on his trunk that would be much more consistent with psoriasis than atopic dermatitis. Although no histologic studies were performed in this patient, the presence of atypical lymphocytes on biopsy specimen would be the primary clue for a diagnosis of cutaneous T-cell lymphoma. Screening for HIV, which may present as an erythroderma, can be useful. In addition, obtaining blood for flow cytometry and Sézary cell count (to assess the potential involvement of blood involvement cutaneous T-cell lymphoma or Sézary syndrome, the leukemic form of cutaneous T-cell lymphoma) and possibly for T-cell receptor gene rearrangement clonality, can also be useful. The most difficult differential diagnosis is often pityriasis rubra pilaris, which not uncommonly presents as a diffuse erythroderma with psoriatic-like scale in a young person. However, the deeply erythematous color of his skin eruption, the lack of “skip” areas, along with a lack of significant keratoderma of his palms and soles make psoriasis the more likely clinical diagnosis in our patient.

Although the patient has diffuse arthralgias, he had no definitive history of PsA. The swelling present in his toes is likely related to his lower leg edema, a common presentation in patients with erythrodermic psoriasis. He has no individual tender “sausage type” joints (known as dactylitis) noted in his toes, making a diagnosis of associated PsA unlikely.

Navigate section 6 of the psoriasis guideline: Case-based review

Citation note

Menter A, Korman NJ, Elmets CA,Feldman SR, Gelfand JM, Gordon KB, Guidelines of care for the management of psoriasis and psoriatic arthritis: section 6. Guidelines of care for the treatment of psoriasis and psoriatic arthritis: case-based presentations and evidence-based conclusions. J Am Acad Dermatol. 2011 Jul;65(1):137-74. 

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