Can Ureaplasma or Mycoplasma Cause Proteinuria?
Yes, Mycoplasma pneumoniae can cause proteinuria and acute glomerulonephritis, though this is rare; however, Ureaplasma urealyticum and Mycoplasma genitalium are genitourinary pathogens that cause urethritis but are not established causes of proteinuria.
Mycoplasma pneumoniae and Renal Disease
Mycoplasma pneumoniae is a documented, albeit uncommon, cause of kidney injury with proteinuria. The evidence shows:
Case reports demonstrate transient massive proteinuria during M. pneumoniae infection, with clinical presentations mimicking nephrotic syndrome 1. Renal biopsies in these cases showed minor glomerular abnormalities with foot process fusion but no immune deposits.
Pediatric series confirm M. pneumoniae-associated nephritis with various histologic patterns including membranoproliferative glomerulonephritis, proliferative endocapillary glomerulonephritis, and minimal change disease 2. These children presented with acute nephritis, nephrotic syndrome, or acute renal failure with proteinuria.
The mechanism appears immune-mediated rather than direct infection, as M. pneumoniae antigens and nucleic acids are typically absent from renal tissue—similar to post-streptococcal glomerulonephritis 2.
Ureaplasma and Mycoplasma Genitalium: Genitourinary Pathogens Only
The genitourinary Mycoplasma and Ureaplasma species have a completely different clinical profile:
Ureaplasma urealyticum:
- Causes 20-40% of nongonococcal urethritis cases 3
- Associated with urethral discharge, dysuria, and urethral inflammation 4
- Not associated with proteinuria or renal parenchymal disease
- Recent data suggest U. urealyticum (but not U. parvum) is a true etiologic agent in NGU 4
Mycoplasma genitalium:
- Recognized cause of nongonococcal urethritis 4
- Presents with mucopurulent discharge and dysuria
- No established association with proteinuria or glomerular disease
Mycoplasma hominis:
- Associated with bacterial vaginosis manifestations 5
- Not independently associated with symptoms in women without BV 5
- No evidence linking it to proteinuria
Clinical Algorithm for Proteinuria Evaluation
When evaluating proteinuria, consider M. pneumoniae only if:
- Recent or concurrent respiratory infection with positive M. pneumoniae serology (IgM by ELISA or immunofluorescence)
- Acute onset of proteinuria or nephritic syndrome
- Absence of other common causes (diabetes, hypertension, primary glomerular disease)
Do not attribute proteinuria to genitourinary Ureaplasma or Mycoplasma species. If these organisms are detected during proteinuria workup, they represent:
- Coincidental colonization (very common—14% of asymptomatic individuals carry U. urealyticum 6)
- Concurrent but unrelated genitourinary infection
- Overdiagnosis from multiplex PCR panels that include these organisms 5
Key Pitfalls to Avoid
Common mistake: Attributing proteinuria to incidentally detected Ureaplasma or Mycoplasma genitalium on multiplex STI panels. These organisms cause urethritis, not glomerular disease 5.
Appropriate workup: If M. pneumoniae-associated nephritis is suspected based on respiratory symptoms and acute proteinuria, obtain M. pneumoniae IgM serology and proceed with standard proteinuria evaluation including renal biopsy if indicated 1, 2.
Treatment consideration: M. pneumoniae-associated nephritis typically resolves with treatment of the underlying infection using macrolides or doxycycline 7, though some cases progress depending on histologic pattern 2.