Granulomatous interstitial nephritis: a chameleon in a globalized world

Two articles in this issue deal with granulomatous acute interstitial nephritis (GIN), a rare disorder seen in 0.5–0.9% of native and 0.6% of transplant renal biopsies [1]. In the first article, Agrawal and co-workers report 10 years of experience with GIN in a tertiary centre in India [2]. In contrast to the experience from Western countries, tuberculosis accounted for more than half of cases. The authors emphasize the challenge of making the diagnosis and recommend a high degree of suspicion [2]. In a second article, Shah and colleagues from the USA [3] review GIN and also highlight current challenges in describing the interesting case of a 69-year-oldmanwithGIN ascribed to doxycycline in whom a positive quantiferon test was received and who eventually died from multi-organ failure. Without autopsy we will never know whether he actually had tuberculosis but their case also reminds us that even with sophisticated testing the cause of GIN remains unclear in a proportion of patients. In this comment, we reflect on both articles and provide some context with an emphasis on pathology and disease patterns worldwide, pitfalls and the diagnostic approach in clinic.