The significance of tubuloreticular inclusions as a marker of systemic stimulation by interferons in a case of focal and segmental glomerulosclerosis associated with cytomegalovirus (CMV) infection

The identification of large numbers of tubuloreticular inclusions (TRIs) in renal biopsies may be useful to raise diagnostic suspicion for certain clinical entities, particularly autoimmune diseases and viral infections. We report a case of a 65-year-old female with a 2-week history of malaise, massive proteinuria and lower extremity edema of acute onset. A renal biopsy was performed and the diagnosis of non-human immunodeficiency virus (HIV) tip-located, early focal segmental glomerulosclerosis (FSGS) was established. The electron microscopy examination was remarkable for the presence of diffuse foot process effacement and frequent TRIs in the endothelial cells of the glomerular capillary loops, endothelium of arterioles and cytoplasm of fibroblasts in the interstitium, highly suggestive of an underlying etiology. Patient clinical and laboratory workup revealed the absence of an autoimmune disease but the presence of a subclinical cytomegalovirus (CMV) infection. Therefore, we highlight that the identification of TRIs is a useful indicator of systemic interferon activity. In the present case, the unusual location of numerous TRIs was associated with a subclinical CMV infection in an immunocompetent patient.