Urinary β(2)-Microglobulin Testing in Pediatric Uveitis: A Case Report of a 9-Year-Old Boy with Renal and Ocular Sarcoidosis

We present here a case of a 9-year-old boy with bilateral anterior uveitis and an extremely elevated urinary β(2)-microglobulin level (25,400 μg/l). The normal range for urinary excretion of β(2)-microglobulin is 0–300 μg/l. In patients with tubulointerstitial nephritis and uveitis syndrome (TINU), elevations typically range from 1,260 to 5,160 μg/l. Renal biopsy was pursued, and significant granulomatous interstitial nephritis consistent with sarcoidosis was identified. Systemic immune modulation was required for control of ocular inflammation. This case highlights the importance of urinary β(2)-microglobulin testing in the pediatric patient uveitis population, and additionally the need to pursue kidney biopsy in the presence of extreme elevations in urinary β(2)-microglobulin to differentiate between TINU and sarcoidosis.