Sézary cell count in exfoliative dermatitis

Sézary cells were present in a number of less than 1000/mm3 in 52 of 78 cases of various benign diffuse dermatoses and mycosis fungoides. The count was higher than 1000/mm3 in two cases of Sézary syndrome in which the histopathology was that of mycosis fungoides and in six cases of exfoliative erythroderma of undetermined etiology with the histopathology of nonspecific chronic dermatitis. One of these six cases developed palmoplantar keratoderma, but abnormal cells were not present in the tissue. The diagnosis of Sézary syndrome in these cases of exfoliative erythroderma could not be established, even though the Sézary cell count was more than 1000/mm3, because the abnormal cells were absent in the skin biopsy specimen. It is concluded that the number of Sézary cells present is not significant for the diagnosis of Sézary syndrome. Our cases with the diagnosis of Sézary syndrome are an erythrodermic variant of mycosis fungoides rather than a progressive conversion from exfoliative erythroderma.