Systemic lupus erythematosus is a systemic autoimmune disease that often affects the kidneys, leading to lupus nephritis. The incidence of kidney involvement depends on the diagnostic criteria. Based on clinical manifestations, kidney involvement occurs in 40–75% of cases, while general pathological examinations reveal a rate as high as 90%. If immunological and electron microscopic examinations are performed, nearly 100% of cases show kidney involvement. Lupus nephritis is a critical factor influencing the prognosis of systemic lupus erythematosus.

bubble_chart Clinical Manifestations

This condition is more common in females, particularly in older children. Renal involvement typically occurs within the first year of systemic lupus erythematosus onset, with rare cases presenting renal involvement as the initial symptom. The severity of renal involvement varies, ranging from microscopic hematuria or proteinuria to acute nephritis syndrome (edema, hematuria, proteinuria, hypertension, and even some degree of azotemia), nephrotic syndrome, rapidly progressive nephritis, or chronic nephritis. In addition to renal involvement, multisystem manifestations are often present, such as fever, rash, arthralgia, anemia, jaundice, subcutaneous hemorrhage, hepatosplenomegaly, lymphadenopathy, palpitation, dyspnea, pericardial friction rub, cardiac insufficiency, pleuritis, and neuropsychiatric symptoms.

bubble_chart Auxiliary Examination

1. Routine blood tests often show mild to grade II anemia, decreased white blood cell and platelet counts, and increased erythrocyte sedimentation rate. 2. Blood complement levels decrease during active disease periods. 3. Lupus erythematosus (LE) cells are positive in 60–75% of cases. 4. Antinuclear antibodies (ANA) are positive in 90% of cases, with titers often exceeding 1:160 during active phases, and immunofluorescence typically shows a peripheral pattern. 5. Anti-DNA antibodies, particularly anti-double-stranded DNA (anti-dsDNA) antibodies, are highly specific. Anti-extractable nuclear antigen (ENA) antibodies, including anti-Smith (Sm) and anti-ribonucleoprotein (RNP) antibodies, are also significant. Although anti-Sm antibodies have a low positivity rate (20–30%), they are highly specific. 6. Other findings include positive immune complexes in the blood, elevated gamma globulin levels, and abnormal urinary sediment (indicative of nephritis), proteinuria, or renal dysfunction, depending on kidney involvement. **(IV) Renal Pathology Examination** The pathological changes in lupus nephritis are complex. The World Health Organization (WHO) classified them in 1974, with further revisions by Churg and Pirani in 1980. The current classification is as follows: - **Class I**: Normal glomeruli or minor glomerular abnormalities. - **Class II**: Mesangial proliferative type (grade I and grade II mesangial proliferation). - **Class III**: Focal segmental type (with mild or grade II mesangial proliferation), featuring necrosis and/or sclerosis. - **Class IV**: Diffuse proliferative type (grade III mesangial proliferation, endocapillary proliferation, membranoproliferative, and crescentic glomerulonephritis, with extensive subendothelial deposits), with or without necrosis or sclerosis. - **Class V**: Membranous type. - **Class VI**: Advanced sclerosing type. Under electron microscopy, lupus nephritis reveals large subendothelial electron-dense deposits. Additionally, findings may include "Sappan Wood" bodies, fingerprint-like structures, and tubuloreticular inclusions. Occasionally, round or oval virus-like particles may also be observed. Immunofluorescence studies predominantly show IgG and C3 deposition, often accompanied by positivity for IgA, IgM, fibrin-related antigens, Clq, C4, and properdin. Immune deposits along the tubular basement membrane and interstitial small vessel walls are also commonly observed.

Systemic lupus erythematosus with clinical renal involvement and/or renal pathological changes can be diagnosed as lupus nephritis. (1) Diagnostic criteria for systemic lupus erythematosus The diagnosis can be confirmed if six of the following criteria are positive. 1. Clinical manifestations (1) Butterfly or discoid rash. (2) Non-deforming arthritis or arthralgia. (3) Alopecia areata. (4) Raynaud's phenomenon and/or vasculitis. (5) Oral mucosal ulcer. (6) Serositis. (7) Photosensitivity. (8) Neuropsychiatric symptoms. 2. Laboratory findings (1) Increased erythrocyte sedimentation rate. (2) Leukopenia <4×10⁹/L, or thrombocytopenia <80 ×10⁹/L, or hemolytic anemia. (3) Proteinuria and/or cylindruria. (4) Hypergammaglobulinemia. (5) Positive lupus cells. (6) Positive antinuclear antibodies. Cases that do not meet the above criteria are considered suspected and should undergo further laboratory tests. Diagnosis can be confirmed if six of the following are positive: (1) Positive anti-DNA antibodies. (2) Hypocomplementemia and/or positive circulating immune complexes. (3) Positive renal biopsy. (4) Positive anti-Sm antibodies.

bubble_chart Treatment Measures

﹝Treatment﹞

(1) Adrenal corticosteroids: Usually, prednisone is administered orally at 1.5–2.0 mg/(kg·d) (total daily dose not exceeding 60 mg), divided into 3–4 doses. Once clinical symptoms are alleviated and laboratory tests return to near-normal levels, the medication is switched to alternate-day oral administration. The dosage is gradually tapered to 0.5–1.0 mg/kg on alternate days, and most children require long-term maintenance therapy. Intravenous methylprednisolone pulse therapy is administered at 15–30 mg/kg (no more than 1000 mg per dose) in 10% glucose solution, with 3 consecutive doses constituting one course. After an interval of several days, the treatment may be repeated. During the intervals and after pulse therapy, prednisone is continued on alternate days. Pulse therapy is indicated for: rapid deterioration of renal function presenting as rapidly progressive nephritis, or lupus nephritis with significant lupus activity, such as lupus encephalopathy, retinal lesions, cardiomyopathy, large pericardial effusion, marked decreases in white blood cells and platelets, etc. Side effects of pulse therapy include hypertension, electrolyte imbalances, arrhythmias, severe infections, diabetes, and rarely, sudden death. (2) Cytotoxic drugs

1. Cyclophosphamide: Cyclophosphamide can suppress T-lymphocyte-mediated humoral immunity, reduce antibody production, improve renal interstitial lesions, and delay or prevent end-stage renal disease. Combined use with corticosteroids can reduce the dosage of steroids, thereby mitigating their side effects. For some severe cases unresponsive to steroids, combination therapy may facilitate disease remission and potentially improve the long-term prognosis of lupus nephritis. Oral administration is at 2–3 mg/(kg·d). For intravenous use, 8–12 mg/kg is added to 100 ml of normal saline and infused over no less than 1 hour, administered for 2 consecutive days every 2 weeks, with a cumulative total dose ≤150 mg/kg. Clinicians should be mindful of its toxic side effects. 2. Other options include azathioprine and chlorambucil. (3) Plasma exchange: This can remove pathogenic antigens, antibodies, and immune complexes from the blood, providing relief for acute and severe conditions. However, about 1 month after the treatment course ends, the condition often deteriorates again, with autoantibodies and immune complexes returning to pre-treatment levels. Therefore, this therapy is only suitable for cases presenting as rapidly progressive nephritis and must be combined with corticosteroids and other immunosuppressive treatments. (4) For patients with declining renal function, appropriate treatment is given based on renal function status, such as dialysis and transplantation. (5) General measures: Avoid direct exposure to sunlight or ultraviolet rays, remove infection foci, prevent infections, and avoid indiscriminate use of medications.