This is a valuable sign for diagnosis, called the Koebner phenomenon. The scalp, knees, elbows, umbilicus, buttocks creases, and genitals are the most common areas of rash. Nail involvement is common and valuable for making the diagnosis. While psoriasis is rare in newborns, it can be a great mimic and resist diagnosis at first. When the first outbreak is in the diaper area, it can mimic seborrheic dermatitis, eczematous diaper dermatitis, perianal streptococcal disease, or yeast infection.
Guttate psoriasis is a variant that occurs predominantly in children.
It is marked by a dramatic eruption of many small, oval or round lesions that morphologically are identical to the larger plaques of psoriasis over the trunk, face, and upper limbs. This eruption often occurs after a streptococcal infection. Guttate psoriasis also may follow perianal streptococcal infection, viral infections, sunburn, and withdrawal of systemic steroid drugs. Treatment of psoriasis can be challenging and should be overseen by a dermatologist. Various preparations are used, including coal tar and salicylic acid.