# FSGS: A Biopsy Pattern with Different Causes

FSGS names a biopsy lesion. Primary, genetic, and secondary disease lead to different treatment decisions.

![Infographic: FSGS: A Biopsy Pattern with Different Causes](https://urinenephrology.org/visual-reference/images/student-fsgs.png?v=20261003c)

## Read the biopsy term correctly

Focal means some glomeruli are affected; segmental means part of an affected tuft is scarred. The lesion does not by itself identify an immune mechanism or establish a need for glucocorticoids.

## Look for a primary clinical syndrome

Abrupt nephrotic syndrome with hypoalbuminemia, extensive foot-process effacement, and no secondary cause supports primary FSGS. Evaluate the complete phenotype; nephrotic-range protein excretion alone is not synonymous with nephrotic syndrome.

## Search for secondary drivers

Review obesity, reduced nephron mass, reflux, viral disease, drugs, and adaptive hyperfiltration. These patients may have substantial proteinuria without the full nephrotic syndrome; treatment should address the driver and supportive kidney protection.

## When genetics changes the question

Early onset, familial disease, syndromic findings, or steroid resistance can justify specialist genetic evaluation. Results may affect treatment expectations, family counseling, and transplant recurrence assessment.

## Make the treatment distinction

Primary FSGS may require immunosuppressive treatment under nephrology care. Secondary FSGS and FSGS of undetermined cause without nephrotic syndrome should not automatically receive immunosuppression; optimize BP/proteinuria care and treat the cause.

## Worked example

An adult with reduced nephron mass, gradual proteinuria, normal albumin, and an FSGS lesion has an adaptive explanation. The next step is cause-directed/supportive care and reassessment, not an automatic high-dose steroid course.

## Supporting evidence

- [KDIGO glomerular disease guideline suite: FSGS](https://kdigo.org/guidelines/gd/)

## Source lessons

- [fsgs student handout](https://urinenephrology.org/student-resources/glomerular/fsgs-student-handout.html)

Read alongside the full lessons; the findings and decisions shown here require the stated clinical context.