This summary discusses psoriasis in infants. Psoriasis in adults and children is addressed separately.

Psoriasis is a chronic inflammatory skin disease that affects approximately 1% of infants and has an unpredictable course with relapses and remissions. It is characterized by an abnormal inflammatory response and a dysregulated proliferation of keratinocytes. Th1, Th17, and Th22 pathways as well as cytokines such as IL-17, IL-23, and tumor necrosis factor alpha (TNF-α) play a central role in its pathogenesis. In genetically predisposed individuals, triggers such as trauma, infections, pollutants, medications, and vaccines can contribute to the appearance or worsening of psoriatic lesions. It also appears to be more common and often more severe in the setting of immunodeficiency.

Infantile psoriasis shares similarities with its adult counterpart, presenting with well-demarcated, erythematous plaques with silvery scales, commonly on the extensor surfaces, scalp, trunk, and lumbosacral / anogenital area. In infancy, psoriatic lesions typically appear on the diaper area (napkin psoriasis) and face, and they tend to be finer, smaller, less scaly, and usually less pruritic. They usually develop gradually but may have a sudden onset, with severity in infancy ranging from mild, limited, and asymptomatic to life-threatening, generalized, exfoliative, or pustular forms. Guttate psoriasis is rarely seen in infancy. It often follows an upper respiratory tract infection, typically streptococcal, and is characterized by the abrupt onset of drop-like papules and small plaques. Nail abnormalities such as pitting, onycholysis, oil spots, and subungual hyperkeratosis may indicate a more severe disease course if present since infancy.