title: Etiological diagnosis of granulomatous tubulointerstitial nephritis in the tropics.
abstract: BACKGROUND
  Granulomatous tubulointerstitial nephritis (GIN) is common due to infections, drugs or sarcoidosis. However, the cause is often difficult to establish and the studies are limited. We studied the etiology of GIN and compared the clinical and histological features and outcome in different etiologies at a tertiary care center in North India.
  
  
  METHODS
  Renaö biopsies from GIN cases diagnosed from January 2004 to April 2014 were retrieved. Stain for acid fast bacilli was performed in all biopsies. Etiological diagnosis was based on clinical features, extra-renal manifestations, radiology, history of drug intake and demonstration of infective agent. Tissue PCR for tubercular DNA was performed in seven biopsies.
  
  
  RESULTS
  Seventeen GIN patients [mean age 35 ± 15 years; males 11] were identified. Tuberculosis was the commonest etiology followed by idiopathic, sarcoidosis and fungal. Both tuberculosis and sarcoidosis patients presented with subnephrotic proteinuria and raised serum creatinine. Acid fast bacilli were demonstrated in 1/9 and necrosis was demonstrated in 3/9 granulomas in tuberculosis. Tissue PCR for tubercular DNA was positive in six TB patients and negative in one sarcoidosis patient. Patients responded well to appropriate therapy.
  
  
  CONCLUSIONS
  Etiological diagnosis of GIN is essential for timely and appropriate therapy. Tuberculosis is the commonest etiology (53%) in the tropics. Necrosis in granuloma, demonstration of acid fast bacilli, blood interferon gamma release assay and urine culture is not sensitive for the diagnosis of tuberculosis in GIN. Our findings suggest that tissue PCR for tuberculosis performed in an appropriate clinical setting is useful in the diagnostic evaluation of GIN.
authors.affiliation: Department of Pathology , Sanjay Gandhi Post Graduate Institute of Medical Sciences , Lucknow, Uttar Pradesh , India.
authors.forename: Vinita
authors.initials: V
authors.lastname: Agrawal
authors.affiliation: Department of Nephrology , Sanjay Gandhi Postgraduate Institute of Medical Sciences , Lucknow, Uttar Pradesh , India.
authors.forename: Anupama
authors.initials: A
authors.lastname: Kaul
authors.affiliation: Department of Nephrology , Sanjay Gandhi Postgraduate Institute of Medical Sciences , Lucknow, Uttar Pradesh , India.
authors.forename: Narayan
authors.initials: N
authors.lastname: Prasad
authors.affiliation: Department of Medical Microbiology , Post Graduate Institute of Medical Education and Research , Chandigarh , India.
authors.forename: Kusum
authors.initials: K
authors.lastname: Sharma
authors.affiliation: Department of Clinical Immunology , Sanjay Gandhi Postgraduate Institute of Medical Sciences , Lucknow, Uttar Pradesh , India.
authors.forename: Vikas
authors.initials: V
authors.lastname: Agarwal
keywords: granulomatous interstitial nephritis; sarcoidosis; tropics; tubercular DNA; tuberculosis