# Isolated renal sarcoidosis and concurrent secondary membranous nephropathy: a case report

## TL;DR

A rare case of kidney sarcoidosis with secondary kidney disease was found in a patient with previously normal tests.

## Contribution

This case report presents a rare instance of isolated renal sarcoidosis with concurrent secondary membranous nephropathy.

## Key findings

- Elevated angiotensin converting enzyme levels can precede overt renal sarcoidosis.
- Secondary membranous nephropathy can occur without overt proteinuria in renal sarcoidosis.
- High-dose corticosteroids stabilized kidney function and resolved symptoms in the patient.

## Abstract

Sarcoidosis is a chronic inflammatory disease characterized by abnormal T-cell responses to unknown antigens. It is a multisystem disorder, affecting the lungs and intrathoracic lymph nodes in over 90% of cases. Isolated renal sarcoidosis, a rare presentation, is confined to the kidneys without systemic involvement.

A 46-year-old African American female was evaluated for persistently abnormal serum creatinine and pyuria. The only abnormality on her noninvasive workup was an elevated angiotensin converting enzyme level for which she was evaluated previously and she was not found to have any manifestations of sarcoidosis. We performed a kidney biopsy that showed findings of renal sarcoidosis and concomitant membranous nephropathy. Patient was treated with high-dose corticosteroids with stabilization of kidney function and resolution of sterile pyuria.

Our case highlights that an elevated angiotensin converting enzyme level can predate the development of an overt renal sarcoidosis. It also shows that findings of a secondary membranous nephropathy can sometimes be seen in the absence of overt proteinuria in sarcoidosis involving the kidneys.