Extraordinary Case ReportLymphomatoid Papulosis Followed by Pityriasis Lichenoides: A Common Pathogenesis?Vonderheid, Eric C MD*†; Kadin, Marshall E MD‡§; Gocke, Christopher D MD†¶Author Information From the Departments of *Dermatology; and †Oncology, Johns Hopkins Medical Institutes, Baltimore, MD; ‡Department of Dermatology, Boston University, Boston, MA; §Roger Williams Medical Center, Providence, RI; and ¶Department of Pathology, Johns Hopkins Medical Institutes, Baltimore, MD. Supported by the Leonard and Ruth Levine Skin Research Fund (E.C.V.) and National Institutes of Health-P20RR018757 (M.E.K.). The authors have no conflicts of interest to declare. Reprints: Eric C. Vonderheid, MD, 37580 S. Desert Sun Drive, Tuscon, AZ 85739-3084 (e-mail: [email protected]). The American Journal of Dermatopathology: December 2011 - Volume 33 - Issue 8 - p 835-840 doi: 10.1097/DAD.0b013e3181f4d8c3 Buy Metrics Abstract Pityriasis lichenoides (PL) and lymphomatoid papulosis (LyP) are uncommon idiopathic eruptions with overlapping clinical and histological features. Although current opinion indicates that PL and LyP are distinct and separate entities, molecular genetic evidence of T-cell clonality in both conditions suggests that an etiopathogenic relationship may exist. We report a patient who was diagnosed with LyP type B in 1985 followed by PL after 11 years. We hypothesize that LyP followed by PL in the same patient reflects differences in the host immune response to a common antigenic stimulus. © 2011 Lippincott Williams & Wilkins, Inc.