Nephrotic and Non-Nephrotic Focal Segmental Glomerulosclerosis: Clinical Characteristics, Etiology, and Columbia Classification.

: Focal segmental glomerulosclerosis (FSGS) is a pattern of kidney injury with diverse causes and pathogeneses, resulting in podocyte injury and depletion. It can be classified as primary, genetic, or secondary. Because FSGS classically has a worse prognosis in patients with nephrotic syndrome, most studies have focused on the treatment and evolution of these patients, resulting in a lack of data related to patients without nephrotic syndrome. The objective of this study was to establish the main etiologies, characteristics, and evolution of renal disease in FSGS patients with nephrotic and non-nephrotic proteinuria. : This was a retrospective, single-center study that included 140 patients with a biopsy-confirmed diagnosis of FSGS in the 2009-2017 period. Patients were separated into those with and those without nephrotic syndrome at diagnosis, and these two groups were compared in terms of the clinical characteristics, histological profile, and outcome. Non-nephrotic patients with unfavorable progression were selected for ultrastructural analysis with electron microscopy. : During the study period, 32.9% of the patients with FSGS had non-nephrotic proteinuria at diagnosis. This group had a larger proportion of patients with hypertension and a not otherwise specified FSGS variant on histology. The proportion of patients with secondary forms of FSGS was comparable between the two groups, with HIV infection and systemic lupus erythematosus being predominant. Progression to renal replacement therapy occurred in 31.3% of the patients in the nephrotic group and in 26.8% of those in the non-nephrotic group, with no statistical difference between them. All of the non-nephrotic group patients who progressed to renal replacement therapy were analyzed by electron microscopy, the diagnosis of FSGS was confirmed, and there was the finding of high chronicity in these patients. : Among patients with FSGS, those without nephrotic syndrome had a poor renal outcome at a frequency similar to that of those with nephrotic syndrome. Factors related to better renal survival were having had a complete response to treatment in the case of those with nephrotic syndrome and having achieved proteinuria values of less than 1.5 g/day in the case of those without nephrotic syndrome.