FIGURE 70.1 Note the linear purplish plaque consistent with koebnerization of lichen planus Pustular psoriasis is rarely seen in children and may arise suddenly Patients may have other forms of psoriasis that then suddenly transition into pustular psoriasis flares, occasionally triggered by use of or withdrawal of systemic corticosteroid therapy Various sizes of sterile and superficial pustules develop on an erythrodermic background Avoidance of systemic steroids may be prudent in patients with psoriasis since withdrawal can precipitate pustular flares of the disease Characteristically small, pitted lesions are seen on the nails in 25% to 50% of patients in all forms of the condition Areas resembling tan-brown oil spots may appear as well within the nails Eighty percent of children have scalp involvement, and patients with early scalp psoriasis may be mistaken for having tinea capitis In contrast to tinea capitis, most cases of psoriatic scalp involvement not show frank hair loss or hair breakage, and scalp lymphadenopathy in psoriasis is uncommon