A penile rash in a child with arthritis

A 9-year-old boy presented with 2 weeks of fever; oligoarthritis involving the right elbow, left knee and elbow; and bilateral conjunctivitis. He had a history of typhoid fever 1 year ago, which was treated and resolved. Investigations showed sterile pyuria, with a white blood cell count of 25 cells per high-power field with negative urine culture, suggestive of urethritis. During the admission, he developed painless, psoriasiform plaques with surrounding erythematous borders and scaling on the glans penis (Figure 1). There was no associated urethral discharge or other mucocutaneous lesions, and the palms and soles were uninvolved. Chlamydia and gonorrhea PCR were negative, and syphilis and human immunodeficiency virus serologies were negative. Penile swab bacterial culture and fungal scraping were unremarkable. HLA-B27 was positive. Autoimmune markers, such as rheumatoid factor and antinuclear antibodies, were negative.