Hypovitaminosis D is Associated with Psoriasis: A Systematic Review and Meta- Analysis ABSTRACT Introduction. Psoriasis is a chronic inflammatory and immunemediated skin disease that affects over 7.2 million U.S. adults. Current treatment has improved clinical outcomes. Vitamin D is believed to affect the proliferation and regeneration of keratinocytes; therefore, its deficiency is a possible risk factor; however, there is still no...