Tubuloreticular inclusions (TRI)s are sub-cellular organelles characterized by small clusters of anastomosing tubule-like structures within cisternae of endoplasmic reticulum and are considered footprints of biological activity of the alpha or beta interferons (IFN-α and INF-β). These structures have been described with collagen vascular diseases (Eg, SLE, systemic sclerosis, MCTD etc.), HIV associated nephropathy and during systemic treatment with interferons. However, the role of TRIs as a reliable indicator of secondary glomerular process with a wide spectrum of etiologies has not been fully studied.
Production of IFNs requires stimulation by viruses, microbial products or specific chemicals via triggering the signaling systems linked to toll-like receptors (TLRs). Both in systemic diseases and viral infections, it’s the IFN-α and INF-β that are most associated with TRI formation. While we have literature supporting some secondary causes that have been associated with TRIs, are we still missing other causes that may lead to a secondary form of GN such as membranous GN, minimal change disease or proliferative GN.
Does the presence of TRI prompt one to look for a secondary cause? What if the only finding you have is TRI with membranous GN and or TRI with MCD? Should a viral etiology or cancer or systemic lupus be considered? Or are we dealing with it backwards. Should we be classifying some of these entities as TRI Nephropathy and then appropriately look for a secondary cause.
In the literature, only one study has looked at TRIs specifically in reference to this question. It was evaluating Membranous GN with TRIs. Most of the cases did lead to a secondary cause but 1/3 had no etiology found( or perhaps we don’t know yet about this virus or systemic disease). Another study did a more wider search and found causes we had already known. Other diverse conditions where TRIs have been described include inclusion body myositis , Kaposi's sarcoma, gliomas and sarcomas. Some of these findings are not in the kidney but in the brain or eye. Perhaps we need to elaborate on disease states that form TRIs and are we missing a bigger entity of TRI related diseases? Inflammatory myopathies are something to strongly consider. Overall, if there is a high IFN-α and INF-β state in the body from any known or unknown cause- chances that it might lead to TRI formation in the kidney and a podocytopathy which can manifest as MCD, Membranous GN, FSGS or proliferative GN.