Lymphomatoid plaquosis - a CD30+ lymphoproliferative rash exhibiting a predilection for recurrence on the same skin sites.

Aberrations in cutaneous T-cell immunology may result in rashes that recur at the same or similar sites in the skin, and include fixed drug eruption, psoriasis and mycosis fungoides (MF). Here we describe a patient with an unusual presentation of a cutaneous CD30 + lymphoproliferative disorder, manifesting as a rash with a tendency to repeatedly appear at the same skin locations before spontaneously clearing. The rash differed clinically from lymphomatoid papulosis (LyP) in that it arose as recurrent plaques which cleared without scarring, and therefore we have termed this condition 'lymphomatoid plaquosis'. A 68-year-old man presented with a 47-year history of an episodic rash consisting of itchy, red scaly patches and plaques. Prior to taking up residence in our region in 2007, he had attended his previous local dermatology department, and due to the complexity of his case and the absence of a definite diagnosis, had attended numerous regional clinical dermatology meetings. Upon presentation to our department, his skin was unaffected, but he mentioned that on each occasion his rash recurred predominantly on the same sites, and showed photographs from 2003 and 2006 (Fig. 1) which seemed to support his view. He mentioned that the skin condition relapsed anytime between 2–7 month intervals, and lasted for 5 days to 2 weeks, after which the rash would clear completely without treatment. The patient later attended a regional clinical dermatology meeting and, despite no obvious precipitant drug, the consensus opinion from the photographs and history included fixed drug eruption, possibly to salicylates or a food colouring, as the most probable diagnosis. The patient was encouraged to attend the dermatology department when the rash recurred but failed to do so (principally because the rash did not trouble him as it always resolved spontaneously). However, in 2012, he was seen when the rash was present on his trunk and limbs in the same sites as in his earlier photographs, and the clinical diagnosis proposed at that stage was cutaneous T-cell lymphoma. Skin biopsies were taken; histology showed acanthosis, spongiosis, parakeratosis, and an infiltrate dominated by large pleomorphic lymphoid blast cells, but also containing small lymphocytes, neutrophil polymorphs and occasional eosinophils in the upper/ mid-dermis (Fig. S1 1). Immunohistochemistry showed that the large atypical lymphocytes expressed CD30 as well as CD3 but not CD4, CD5 or CD8. Occasional lymphocytes, neutrophils and blast cells permeated into the epidermis, however there were no overt features of MF, …