Case Presentation: Lupus nephritis (LN) is a clinical manifestation of SLE that can be histologically categorized from class I-VI. One form of LN that is not included in the classification is lupus podocytopathy (LP). LP is a somewhat rare manifestation of SLE associated nephrotic syndrome that mimics minimal change disease (MCD) and is diagnosed via renal biopsy. LP represents approximately 1% of lupus nephritis biopsies.1 A 44 year old female with a family history significant for SLE presented to the emergency department (ED) for bilateral lower extremity and abdominal swelling. A urinalysis was performed which showed proteinuria and an elevated total protein/creatinine ratio of 5906 mg/g. Patient was discharged home on furosemide and advised to follow up with cardiology and nephrology. Outpatient rheumatologic workup was notable for a positive ANA (1:640) speckled and positive RNP with otherwise negative serology including ds-DNA, normal SPEP with immunofixation, hepatitis B/C, antistreptolysin O and normal complement levels. Two weeks later, the patient returned to the ED for bilateral lower extremity cramping. She was admitted for an acute kidney injury, with a baseline creatinine of 0.54, now elevated to 1.04. A renal biopsy showed histologically unremarkable glomeruli with minimal tubular atrophy and interstitial fibrosis. Immunofluorescence demonstrated tissue ANA correlating with the patient’s positive serum ANA without significant glomerular staining for antisera. Electron microscopy showed 100% foot process effacement of podocytes, findings which are consistent with MCD. However, given the patient’s positive serum ANA and family history of SLE the biopsy confirmed LP. She was discharged home on prednisone, bumetanide and hydroxychloroquine. At follow up one month, patient’s urine total protein/creatinine ratio improved to 486.
Discussion: LP is a newly recognized form of LN that mimics MCD where there is foot process effacement without immune complex deposition.2 In patients with undiagnosed SLE presenting with nephrotic syndrome, LP can be difficult to diagnose. Renal biopsy is the gold standard for diagnosis of nephrotic syndrome. Ultimately, this patient’s biopsy showed MCD, but in the context of a positive ANA, LP was the diagnosis. LP is treated in the same manner as MCD with high dose steroids.4 In our case, patient’s proteinuria did improve with initiation of steroids and hydroxychloroquine. In one study, 47 of the 50 LP cases that were analyzed achieved remission with immunosuppressive therapy after 4 weeks.3 The exact pathophysiology of LP is still unknown, although one hypothesis is that podocytes are in fact immunologically active cells that also act as antigen presenting cells which precipitate an immune response.4
Conclusions: This case illustrates a rare form of LN and emphasizes the importance of thorough history taking. Definitive diagnosis is made with a renal biopsy and the treatment for LP is the same as MCD with high dose steroids and possibly other immunosuppressive agents.