Two patients with recurrent generalized pustular psoriasis of von Zumbusch were studied. Systemic manifestations of this disease included hepatitis, fever, leukocytosis, hypoproteinemia, hypocalcemia, and elevations of serum transaminase and alkaline phosphatase levels. Typical attacks were induced by challenge with 500 mg of orally administered potassium iodide. Salicylates also appeared to have an adverse effect. By strict avoidance of iodides and salicylates prolonged complete remissions were achieved in both patients. However, in one patient premenstrual flares occurred and a single oral challenge with 5 mg of progesterone was followed by a minor clinical attack of pustular psoriasis. It is postulated that iodides trigger attacks by stimulating the activity of cellular dihydrofolic reductase, essential in the metabolic pathways involved in the cell division necessary for the clinical expression of the disease. Inhibition of this enzyme by folic acid antagonists is known to produce remissions in the disease. Further study of the folic acid pathway in psoriasis is needed.
Shelley WB. Generalized Pustular Psoriasis Induced by Potassium Iodide: A Postulated Role for Dihydrofolic Reductase. JAMA. 1967;201(13):1009–1014. doi:10.1001/jama.1967.03130130035009
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