The exact nosological position of this condition remains obscure. However, since it has certain of the features of eczema and is not infrequently mistaken for it, it is considered here. It occurs equally in the two sexes and is commonest between the ages of 40 and 50. Although no more a variant of psoriasis than of eczema, it appears four times more frequently in psoriatics and this explains its title. It is characterized by flat, yellow sterile pustules occurring under the horny layer of the epidermis of the palms and soles. The pustules may occur symmetrically on both hands, commonly on the thenar or hypothenar eminences, or on both feet, commonly under the insteps. Or they may appear on one hand or one foot only or on all four extremeties. They are accompanied by slight or moderate discomfort or irritation. The pustules dry up, turn brown and then exfoliate, while fresh ones continually appear. It is one of the most intractable of all skin diseases.
Diagnosis
It must be distinguished from secondarily infected eczema or dermatitis. In such cases the pustules are usually much larger and more prominent and there is much more inflammation, pain and disability. Culture from the pustules will grow an infecting organism, usually a staphylococcus. These characteristics apply equally to
Secondarily infected vesicular ringworm of the soles, but here fungus can also be seen in the roofs of the lesions on microscopic examination.