Kidney Disease in a Patient With a Chronic Rash: A Quiz

A 66-year-old man was referred to our hospital for chronic kidney disease of unknown etiology of at least 1-year duration and non–nephrotic-range proteinuria. His medical history included hypocomplementemic urticarial vasculitis syndrome (HUVS) diagnosed 16 years earlier, with cutaneous and rheumatologic manifestations (arthritis of both hands). He was currently taking prednisolone 5 mg per day, but had previously been treated with azathioprine (stopped for hepatotoxicity) and hydroxychloroquine (stopped for retinopathy). The patient reported persistent rash and arthritic symptoms for several years despite use of prednisolone. Physical examination findings included diffuse rash (Fig 1) and osteoarthritis of the hands. Relevant initial laboratory results are presented in Table 1. Serum immunofixation was positive for 2 monoclonal components (IgMκ and IgGκ), and free light chain ratio was normal (adjusted to his estimated glomerular filtration rate [eGFR]). A kidney biopsy was performed (Fig 2A-C).