Page 484 - Concise Pathology for Exam Preparation ( PDFDrive )

16 Diseases of the Kidney and Lower Urinary Tract 469

2. Hyperlipidaemia which is due to:
1. Enhanced synthesis of lipoproteins in liver
2. Abnormal transport of circulating lipid particles
3. Reduced catabolism of lipids
The lipid-related metabolic abnormalities seen in nephrotic syndrome are
• Increased cholesterol, triglycerides, VLDL, LDL, LP (a) and apoproteins
• Decrease in HDL (loss in urine)
• Lipiduria or oval fat bodies or free fat in urine (lipoproteins reabsorbed by tubular
epithelium and then shed with the epithelium when it gets injured and detached)
3. Thrombotic complications: Renal vein thrombosis due to loss of anticoagulant factors,
eg, antithrombin III (AT III)
4. Increased susceptibility to infection: Due to loss of immunoglobulins in the urine

Causes
• Primary glomerular diseases:
• Membranous glomerulonephritis
• Lipoid nephrosis
• Focal segmental glomerulosclerosis (FSGS)
• Membranoproliferative glomerulonephritis (MPGN)
• IgA nephropathy
• Systemic diseases:
• Diabetes mellitus (DM)
• Amyloidosis
• SLE
• Drugs (gold, penicillamine and street heroin)
• Infections (malaria, syphilis, hepatitis B and AIDS)
• Malignancy (carcinoma and melanoma)
• Miscellaneous (bee-sting allergy and hereditary nephritis)

Membranous Glomerulonephritis
Pathogenesis
• Primary or idiopathic membranous nephropathy is thought to be an autoimmune dis-
ease linked to a susceptibility gene like HLA-DQA1. It is caused by an in situ immune
reaction involving renal autoantigens (eg, PLA2R) and in some cases, planted antigens.
The disease shows resemblance to Heymann nephritis (induced by formation of anti-
bodies to the megalin antigenic complex present in rat podocytes which is the animal
counterpart of PLA2R).
• Circulating immune complexes are present in 25% cases.
• Paucity of neutrophils, monocytes and platelets in glomeruli and virtually uniform pres-
ence of complement points to direct action of C5b-9 (membrane attack complex),
which is thought to activate glomerular epithelial and mesangial cells to release prote-
ases and oxidants, which cause capillary wall injury to lead to protein leakage.
Causes
Idiopathic (primary) in 75% cases; the remaining 25% are labelled secondary and may
be caused by:
• Malignancies (carcinoma lung/colon/melanoma)
• SLE
• Exposure to inorganic salts (gold and mercury)
• Drugs (penicillamine and captopril), gold and NSAIDs
• Infections (hepatitis B and C, syphilis, schistosomiasis and malaria)
• DM and thyroiditis
Morphology (Fig. 16.6)
Light microscopy: The early stages show no abnormality; later, uniform and diffuse thickening
of the glomerular capillary wall due to IgG deposits along the epithelial side of the basement
membrane is noted.

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