Introduction: Autoimmune polyendocrine syndrome type I (APS I) is an autosomal recessive systemic autoimmune disorder, affecting primarily endocrine glands, in which chronic mucocutaneous candidiasis is an early and prominent manifestation. We describe the rare occurrence of unstable psoriasis (with onset of pustular lesions) in a case of APS I without mucocutaneous candidiasis. A patient presenting with unstable psoriasis (with onset of pustular lesions) was detected to have persistent hypocalcemia which led to the diagnosis of hypoparathyroidism. Subsequently he was found to have hypergonadotrophic hypogonadism, primary adrenal insufficiency (compensated), and coeliac disease, thus confirming the diagnosis of APS I. Psoriasis is very rarely reported in APS I, possibly due to the protective effect of antibodies to Th17 cytokines, which are responsible for the occurrence of candidiasis in this syndrome. However, psoriasis could occur in APS I patients without mucocutaneous candidiasis, who lack these antibodies. In our patient, possible factors aggravating psoriasis include hypocalcemia due to hypoparathyroidism as well as coeliac disease via anti-tissue transglutaminase antibodies. However, defining psoriasis as a possible minor component of APS I would require further studies of the autoimmune regulator (AIRE) gene functions.