Psoriatic erythroderma: a histopathologic study of forty-five patients

There are conflicting opinions about the diagnostic value of skin biopsy in erythrodermic psoriasis.

The purpose of the present study was to establish the specificity of the histopathologic changes of psoriatic erythroderma.

We reviewed 52 skin biopsies from 45 erythrodermic patients having a final diagnosis of psoriasis on the basis of combined clinical and laboratory data, in addition to response to therapy and follow-up. In 5 patients, erythroderma was the presenting sign of psoriasis. A control group of nonpsoriatic erythrodermic patients was also included in the study.

Among the group of patients with a discharge diagnosis of psoriatic erythroderma, the histopathologic changes were specific for psoriasis in 40 cases (88%). The changes of early macular and squamous lesions of psoriasis were more often found in the biopsy specimens of our series than those of fully developed or late lesions of psoriasis. They included mainly slight epidermal hyperplasia, focal disappearance of the granular layer, mounds of parakeratosis and extravasated erythrocytes within edematous dermal papillae associated with perivascular and interstitial infiltration of lymphocytes and histiocytes.

When features of early lesions of psoriasis are found during the evaluation of a biopsy specimen from a patient with a clinically nonspecific erythroderma, the dermatopathologist should be aware that this patient could have psoriasis and a renewed anamnesis and a close follow-up should be made.