NEFRITE TÚBULO-INTERSTICIAL CRÔNICA ISOLADA NO LÚPUS ERITEMATOSO SISTÊMICO – UM ACOMETIMENTO RARO: UM RELATO DE CASO

Systemic lupus erythematosus (SLE) is a chronic and inflammatory autoimmune disease that can affect several organs and tissues, with the kidneys being the most frequently affected. Tubulointerstitial nephritis, which can be secondary to autoimmune diseases, medications, toxins and radiation, rarely presents with isolated renal involvement. In this context, we report the case of a 64-year-old female patient diagnosed with chronic active tubulointerstitial nephritis after the diagnosis of SLE. During the etiological investigation, the patient presented hypertension and, in the exams performed, the fundoscopy revealed no significant alterations. The ANA was positive (1/1280, fine speckled homogeneous nuclear pattern), with consumed complements C3 and C4, in addition to a positive test for anti-DNA, hemolytic anemia and presence of serositis, evidenced by a pericardial effusion on the echocardiogram. These findings culminated in the diagnosis of SLE. A renal biopsy was performed, followed by the initiation of pulse therapy with methylprednisolone (500 mg per day for 3 days), but without clinical or laboratory response. The biopsy revealed active chronic tubulointerstitial nephritis, with deposition of immune complexes, probably associated with SLE, without evidence of glomerular involvement. This characterizes an isolated Chronic Tubulointerstitial Nephritis, a rare manifestation of lupus nephritis. After this diagnosis, supportive measures and immunosuppressive treatment were implemented, including hemodialysis, antihypertensives, hydroxychloroquine (400 mg per day), corticosteroids and cyclophosphamide (1 gram per month for the first six months). Chronic tubulointerstitial nephritis is characterized by insidious tubular aggression, with gradual interstitial infiltration, fibrosis and tubular atrophy, resulting in renal dysfunction and progressive deterioration of renal function over the years. Symptoms are usually nonspecific and varied. The prognosis depends on the etiology, treatment and patient response, with the aim of preventing the occurrence of irreversible fibrosis. Tubulointerstitial disease, with or without immune deposits, is a rare finding in patients with SLE.