Every dermatology resident preparing for their board examination can rattle off Griffiths’ classification of pityriasis rubra pilaris (PRP) – Type I (Classical Adult), Type II (Atypical Adult), Type III (Classic Juvenile), Type IV (Circumscribed Juvenile), and Type V (Atypical Juvenile). Type VI, associated with HIV infection was subsequently added to the list.
I have never been pleased with the diagnosis of PRP, in the same way that diagnosing erythema nodosum is unsatisfying – a label is placed on lesions with a distinct pattern, however, the etiology is obscure. Understandably, when we observe a papulosquamous eruption with some degree of follicular accentuation, keratoderma, and islands of sparing, PRP will be diagnosed. Perhaps it will even be characteristic enough to be classified as a Griffiths type.
From my perspective, since the Griffiths classification is entrenched, at least two more categories need to be added. Paraneoplastic PRP should be Type VII. An example is a case of colon cancer associated with classical features of PRP in an 89 year-old woman with a prior history of psoriasis. One month after a right hemicolectomy, her PRP was almost completely clear. (It is possible that her PRP also just resolved spontaneously) (1). A PubMed search of “paraneoplastic” PRP does not yield many cases, although an association of PRP has been reported with metastatic squamous cell carcinoma, bronchogenic carcinoma, adenocarcinoma of the lung, laryngeal carcinoma, and renal cell carcinoma.
Type VIII would be Sézary syndrome (SS) presenting as PRP. According to Nagler et al “Erythrodermic cutaneous T-cell lymphoma can mimic a number of nonmalignant disorders with erythroderma, including pityriasis rubra pilaris, psoriasis, atopic dermatitis, and graft-versus-host disease. The diagnosis is made even more challenging because the histology of SS is often nonspecific and rarely pathognomonic. As a result, peripheral blood studies in patients with erythroderma are frequently informative in the diagnosis of SS. Peripheral blood abnormalities including elevated CD4/CD8 ratio, aberrant CD26, CD27 and CD7 expression, and T-cell clonality can all be used to help arrive at a diagnosis (2).” Although a T cell clone does not define SS in and of itself, a matching clone in the blood and skin make the diagnosis plausible. Clues to securing the diagnosis may include a peripheral eosinophilia. Skin biopsies need not show features of CTCL, and may be interpreted as psoriasiform or consistent with PRP. Such a patient* was recently presented at Penn where Dr. Alain Rook (the senior author reference 2) astutely commented that he has seen many cases of SS mimicking PRP – he warned that immunosuppressive treatments including cyclosporine, or biologic agents such as TNF-alpha inhibitors, are contraindicated in these patients.
Pfister-Wartha and Schempp described the case of a 67-year-old man with PRP that did not respond to acitretin or steroids (systemic and topical). Scaling and pruritus improved within 3 weeks of administration of secukinumab, and by week 8 pruritus and erythema resolved. Because spontaneous resolution could not be excluded, the authors appropriately recommended further studies of IL-17 antagonists in PRP (3).
Aside from retinoids, methotrexate, and phototherapy, TNF-alpha inhibitors have been utilized in treating PRP. Secukinumab (Cosentyx) and ixekizumab (Taltz) are IL-17 inhibitors; brodalumab, an IL-17 receptor inhibitor, is in the pipeline. Although secukinumab carries no increased of leukemia or lymphoma (4), presumably its use is contraindicated in patients with lymphoproliferative disorders.
Therapeutic decisions are optimally rooted in a secure diagnosis. Before prescribing immunosuppressive agents in erythrodermic PRP patients, make sure that they are not type VIII.
- Vitiello M, et al. Pityriasis rubra pilaris: Was it the first manifestation of colon cancer in a patient with pre-existing psoriasis? J Am Acad Dermatol 2013; 68: e43-4.
- Nagler AR, et al. Peripheral blood findings in erythrodermic patients: Importance for the differential diagnosis of Sézary syndrome. J Am Acad Dermtol 2012; 66: 503-8.
- Pfister-Wartha A, Schempp CM. Successful treatment of refractory pityriasis rubra pilaris with secukinumab. JAMA Dermatol 2016; 152: 1278-80.
- Blauvelt A. Safety of secukinumab in the treatment of psoriasis. Expert Opin Drug Saf 2016; 15: 1413-20.
*Permission granted by the patient to publish his images