INTRODUCTION
Pityriasis rubra pilaris (PRP) is a rare papulosquamous eruption of unknown etiology. Peak occurrences are during the first and sixth decades and both sexes are equally affected. Proposed etiologies for PRP include vitamin A deficiency, autoimmune processes, and human immunodeficiency virus.1,2 We report a case of a patient who presented with recalcitrant paraneoplastic PRP as the presenting manifestation of metastatic squamous cell carcinoma
CASE REPORT
An 83-year-old Caucasian male with a past medical history of melanoma and acute myelogenous leukemia presented with a four month history of a pruritic red, scaly rash, that started on the chest and spread to the neck, face, back, arms, and legs. His physical exam revealed erythematous, scaly papules, and plaques with slight orange hue on the face, upper chest, back, arms, and legs. There were also small islands of sparing within more confluent areas (Figure 1a,b). A punch biopsy performed previously at an outside clinic was consistent with psoriasiform dermatitis. The patient was treated for several months with topical triamcinolone and clobetasol. After failure to respond to therapy, the patient was referred to our clinic, where we repeated a biopsy, which was consistent with pityriasis rubra pilaris (Figure 2).
Concurrent to our evaluation of the patient for PRP, the patient developed a chronic productive cough. A screening chest x-ray ordered by his primary care physician revealed interval change in mediastinal fullness, concerning for neoplasm (Figure 3a). A follow up F-18 fluorodeoxyglucose positron emission tomography with computed tomography (FDG-PET/CT) scan of the chest revealed a large, hypermetabolic paratracheal mass and lung nodules suspicious for metastatic disease (Figure 3b). Fine needle aspiration of the primary tumor demonstrated undifferentiated squamous cell carcinoma, and the patient was subsequently treated with radiation and paclitaxel chemotherapy. Simultaneous to his treatments, the patient’s PRP resolved nearly completely without any other continued topical or systemic therapy. Following radiation and chemotherapy, a follow up FDG PET/CT demonstrated markedly decreased metabolic activity of the primary paratracheal tumor (Figure 3c). The resolution of the rash with radiation and chemotherapy suggests a direct relationship between the PRP and the malignancy.
DISCUSSION
Pityriasis rubra pilaris is a papulosquamous eruption of unknown etiology that usually presents with orange-red scaly papules that coalesce into plaques with characteristic areas of sparing. The palms and soles may develop a similar orange-red, waxy keratoderma, and erythema with diffuse scale may be seen on the scalp as well. There are five types of PRP, with the classical adult onset subtype being the most common. In the classical variant, the eruption typically progresses in a caudal direction and has been associated with pruritus and burning sensations.
