Umbilical Plaque in Psoriatic Arthritis

A 68-year-old man was referred to us with glucocorticoidresistant polyarthralgia. Three months before presentation, he received a tentative diagnosis of polymyalgia rheumatica and was treated with prednisolone (10 mg/day) by an orthopedic surgeon. The findings for rheumatoid factor and anticitrullinated peptide antibody were negative. After his polyarthralgia improved, the prednisolone was gradually tapered, but the polyarthralgia soon recurred. Readministration of prednisolone was less effective the second time. His C-reactive protein level was 3.5 mg/dL under treatment with prednisolone at 10 mg/day. On examination, he had pain in the neck and right shoulder joint and arthritis of the right ankle, as well as a rash resembling seborrheic dermatitis at his hairline. After removing his shirt, a large, thick, pink-whitish plaque was seen at the umbilicus (Picture 1). In addition, there was a red-purple scaly rash on his back (Picture 2), and the nail of his right thumb was yellow (Picture 3). A dermatologist diagnosed the patient to have psoriasis. We therefore diagnosed the joint involvement as being due to psoriatic arthritis (1). After treatment with adalimumab, his joint symptoms and skin lesions gradually improved.