Acute Diffuse Glomerulonephritis: Differential Diagnosis of Lupus Nephritis

Abstract

BACKGROUNDAcute diffuse glomerulonephritis is one of the most prevalent causes of glomerulonephritis worldwide. Children of preschool age are the most affected age group, being rare in adults over 40 years old. Treatment is symptomatic and the prognosis is favorable in most cases. CASE REPORTFemale patient, 42 years old, in 2019 started with a recurrent urinary infection. During the investigation, the presence of proteinuria was evidenced, an ANA was requested, which was reactive and a renal biopsy was indicated, but not performed at the time due to loss of follow-up. In January 2020, she developed malar rash, photosensitivity, alopecia, inflammatory rhythm arthralgia in metacarpophalangeal and proximal interphalangeal joints. After an irregular external follow-up period and with a report of shortterm use of hydroxychloroquine and methotrexate, in August 2021 she was referred to our service. When the diagnostic hypothesis of systemic lupus erythematosus (SLE) was raised, tests were requested for diagnostic investigation, with fine speckled nuclear ANA 1:160, C3 hypocomplementemia, reagent anticardiolipin IgM and 24-h proteinuria of 957 mg. Due to the diagnosis of SLE with persistent proteinuria without loss of renal function, it was decided to perform a renal biopsy to better elucidate the condition before instituting immunosuppression. The biopsy showed 23 glomeruli with mild to moderate hypercellularity, with reduced capillary lumen and occasional neutrophils in these areas, 2 of them with a focus of fibrinoid necrosis. The immunohistochemistry showed as alteration the presence of complement, positive C3 fraction 3+/3+ with coarse granular pattern, of global and diffuse distribution in capillary loops. The morphological findings associated with the immunofluorescence exam correspond to acute diffuse intracapillary glomerulopathy (post-streptococcal glomerulonephritis). Since the patient meets the criteria for SLE, with proteinuria, but with renal biopsy not suggestive of lupus nephritis, but of another pathology (ADGN), it was decided to introduce methotrexate 12.5 mg/week, prednisone 20 mg/day due to cutaneous activity and articulate. The patient evolved with resolution of proteinuria and normalization of C3 with the instituted treatment. CONCLUSIONThe presence of proteinuria in SLE patients should draw our attention to one of the most serious complications of this disease, which is lupus nephritis. However, its differential diagnosis is extensive and renal biopsy should be performed whenever possible, since other diagnoses may not require immunosuppression.