GABARITO: ALTERNATIVA D

Explanation:

Systemic lupus erythematosus (SLE)

Clinical features

Systemic symptoms: low-grade fever, generalized fatigue, and unintentional weight loss
Musculoskeletal: symmetric, migratory joint pain or arthritis
Dermatologic: malar (butterfly) rash and increased sensitivity to sunlight
Serosal involvement: inflammation of pleura (pleuritis), pericardium (pericarditis), or peritoneum (peritonitis)
Thrombotic complications: arterial or venous thrombosis, often related to vasculitis or the presence of antiphospholipid antibodies

Laboratory findings

Hematologic abnormalities: immune-mediated hemolytic anemia, thrombocytopenia, and leukopenia
Complement levels: decreased C3 and C4 due to complement activation
Autoantibodies: antinuclear antibodies (high sensitivity); anti–double-stranded DNA and anti-Smith antibodies (high specificity)
Renal involvement (lupus nephritis): proteinuria and elevated serum creatinine

This young woman presents with chronic migratory arthralgias, pancytopenia, and glomerulonephritis (evidenced by proteinuria and red blood cell casts), a constellation of findings suggestive of systemic lupus erythematosus (SLE)—a chronic, idiopathic autoimmune disease most commonly seen in women of reproductive age. Although a malar or photosensitive rash is a classic feature, cutaneous involvement is not required for diagnosis and may be absent in some cases.

Hematologic manifestations are frequent in SLE. Anemia is often due to chronic inflammation (anemia of chronic disease), but pancytopenia may result from autoantibody-mediated destruction of erythrocytes, leukocytes, and platelets (a type II hypersensitivity reaction). Autoimmune hemolytic anemia in SLE involves IgG antibodies against red blood cells, leading to extravascular hemolysis, spherocytosis, and a positive direct Coombs test. Thrombocytopenia may resemble immune thrombocytopenic purpura due to antiplatelet antibodies, and neutropenia can occur via immune destruction.

Renal involvement, or lupus nephritis, results from immune complex deposition (type III hypersensitivity) within various regions of the glomerulus, including the mesangium, subendothelial, and subepithelial spaces. While histologic patterns vary, the most common and severe form is diffuse proliferative glomerulonephritis (class IV).

Educational Objective:

Systemic lupus erythematosus should be suspected in young women with migratory arthralgias, pancytopenia, and glomerulonephritis. Hematologic abnormalities result from autoantibody-mediated destruction of blood cells (type II hypersensitivity), while renal involvement reflects immune complex deposition (type III hypersensitivity). Diagnosis is supported by serologic markers (e.g., ANA, anti-dsDNA, low complement) and confirmed by clinical criteria.

Answer Choice Explanations: