Fibrillary Glomerulonephritis in 2026: Why Treatment Remains a Challenge

Fibrillary glomerulonephritis (FGN) remains one of the least-studied glomerular diseases in nephrology, accounting for less than 1% of kidney biopsies and offering clinicians few evidence-based treatment options.

With DNAJB9 staining now able to separate FGN from look-alike entities and data available from the multicenter FACT trial, clinicians have a clearer, if still incomplete, framework for management.

In this 8-part HCPLive special report, "Management of Fibrillary Glomerulonephritis in 2026," Gerald Appel, MD, co-director of the Glomerular Kidney Center at Columbia University Irving Medical Center, is joined by fellow co-director Andrew Bomback, MD, MPH, to discuss how they approach diagnosis, treatment, and non-response in this ultra-rare disease.

The segment opens with Bomback asking what makes FGN so difficult to treat compared with other glomerular diseases. Appel points to rarity as the core obstacle. Because diagnosis depends entirely on kidney biopsy, he explains, enrolling enough patients to study the disease, or even to follow its natural history, has been hard. He adds that FGN was historically confused with immunotactoid glomerulonephritis, an entirely different disease, and that better markers should support more studies and collaboration going forward.

The conversation then turns to the FACT trial, a multicenter study conducted at glomerular centers across the United States in patients with DNAJB9-positive FGN. Bomback describes a design that randomized patients to ACTH alone or ACTH plus tacrolimus. He emphasizes that the trial's success begins with its completion, which demonstrated that patients with FGN can be enrolled in randomized studies that generate robust data.

Bomback notes that about 56% of patients across both arms achieved a complete or partial proteinuria remission by 12 months, establishing ACTH, alone or with tacrolimus, as an antiproteinuric option for some patients. He cautions, however, that nearly half of patients did not respond and that durability remains unknown, particularly whether proteinuria rebounds once therapy stops.

Appel closes the segment by noting that both he and Bomback co-authored the study. He acknowledges its limitations, including the lack of a placebo control, limited follow-up, and small numbers, while observing that it is the evidence clinicians currently have.