# Beneath the Surface: A Rash That Uncovered Renal Autoimmunity

## TL;DR

A man with a rash and kidney issues was diagnosed with lupus nephritis, and early treatment improved his condition.

## Contribution

This case highlights the importance of early diagnosis and treatment in lupus nephritis through clinical and histopathological findings.

## Key findings

- Elevated anti-dsDNA and hypocomplementemia supported a diagnosis of systemic lupus erythematosus.
- Kidney biopsy confirmed Class III lupus nephritis with full-house immunofluorescence staining.
- Timely immunosuppressive therapy led to clinical improvement and stabilized kidney function.

## Abstract

We report the case of a 42-year-old male who presented with a generalized rash, acute kidney injury, anemia, and positive antinuclear antibodies (ANA). Serologic testing revealed elevated anti-double-stranded DNA (dsDNA) levels and hypocomplementemia, raising concern for systemic lupus erythematosus (SLE). Kidney biopsy confirmed Class III (focal proliferative) lupus nephritis according to the International Society of Nephrology/Renal Pathology Society 2003 classification. Immunofluorescence demonstrated full-house staining (positive for IgG, C3, C1q, and light chains) with weaker signals for IgA and IgM. Electron microscopy revealed subepithelial and mesangial electron-dense deposits. Early recognition and timely initiation of immunosuppressive therapy led to clinical improvement and stabilization of renal function.