Pityriasis rosea. This benign and self-limited eruption occurs most often in spring and autumn. Most patients are adolescents and young adults, but the disorder is not unusual in children and may even occur during infancy. In its classic form, pityriasis rosea follows a specific and predictable clinical course. The first solitary lesion is a circle or oval of erythema and scaling. As it develops to its full size of up to 2–3 cm, this so-called herald patch may easily be mistaken for a lesion of tinea corporis. The chest and upper thigh are common locations for the herald patch but any area may be involved. A typical herald patch is shown here.
Neurofibromatosis (von Recklinghausen’s disease). This autosomal dominant disorder includes a number of distinctive cutaneous findings and a wide variety of neurologic manifestations. This picture shows a café-au-lait spot. Solitary lesions of this type are common in normal individuals; most patients with neurofibromatosis have more than a single macule. The presence of more than six lesions that are larger than 0.5cm in diameter in prepubescent children and 1.5 cm in diameter in adults is considered one of the major diagnostic criteria for this disease.