Regional lymphomatoid papulosis: a report of four cases.

Lymphomatoid papulosis (LyP) is a chronic self-healing cutaneous eruption which is clinically benign but histologically malignant. Lesions occur episodically over the trunk and limbs. We describe four patients with regional LyP. All were male, with a range in age at onset from 12 to 47 years. In all cases, lesions were confined to a segmental unilateral area. Two patients had type A and two type B LyP. We have long-term follow-up on one patient whose lesions were limited to the right buttock for more than 20 years before more widespread lesions developed. Another patient with lesions on the left flank had mycosis fungoides limited to the same region. Only one other case of LyP presenting in a regional distribution has previously been described.