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Chapter 6: Disorders of the kidney 249

Investigations Table 6.10 Major causes of membranous nephropathy
In adults, renal biopsy is normally needed for diagno-
Malignancies Lung, colon, breast cancer
sis. In children renal biopsy is only indicated in pa- Haematological less often
tients with atypical features or who do not respond to Autoimmune disease SLE
treatment. Rheumatoid arthritis
Drugs Penicillamine, gold
Management NSAIDs
Infections Hepatitis B, hepatitis C
Themainstayoftreatmentiswithcorticosteroids,with

Malaria, schistosomiasis, syphilis
complete remission of proteinuria in over 90% of Miscellaneous Chronic renal transplant rejection
cases.Proteinuriamaytakeupto3or4monthstocom- Sarcoidosis
pletely disappear. Relapse can occur when steroids are Other glomerular diseases
reduced. Cyclophosphamide, cyclosporine and other
drugs have also been used to induce remission in Pathophysiology
steroid-resistant cases, or to reduce the steroid dose The mechanism is unknown. It is thought that antibod-
in those who are steroid-dependent. ies directed against antigens in the subepithelial space
Patients may also require anti-coagulation and peni- form immune complexes. In idiopathic MN, these are

cillin prophylaxis. probably autoantibodies, whereas in secondary causes
circulating antigen is filtered by the kidney, leading to de
Prognosis
novoimmunecomplexesorpossiblycirculatingimmune
Progression to CRF is very rare in those with true MCD.
complexes. Because the immune deposits are subepithe-
Repeat renal biopsy may demonstrate another condition
lial there is usually no marked inflammatory response.
such as focal segmental glomerulosclerosis in those who
The BM becomes more permeable to protein, lead-
do not respond to treatment.
ing to proteinuria and the nephrotic syndrome. Over
many years, there is increase in mesangial matrix caus-
Membranous glomerulonephritis ing hyalinization of glomeruli and loss of nephrons.
Definition Clinical features
This is the one of the two most common causes of Patients may present with asymptomatic proteinuria,
nephrotic syndrome in non-diabetic adults (together or (in most cases) nephrotic syndrome. There may be
with focal segmental glomerulosclerosis). Also called features consistent with an underlying disease, partic-
membranous nephropathy (MN), glomerulonephropa- ularly malignancies, which is usually overt at time of
thy or glomerulopathy. presentation.
Macroscopy/microscopy
Incidence/prevalence
Renal biopsy shows thickened capillary loops (ranging
MN accounts for as many as 25–30% of cases of adult
from mild in early disease, to marked in late disease),
nephrotic syndrome. The idiopathic form causes ∼20%
usually with mild to moderate mesangial proliferation.
of cases, although this varies by population.
Silver stains classically show ‘spikes’ where basement
membrane has grown between subepithelial deposits.
Age
Immunofluorescence shows immune complexes (IgG,
Peak age 30–50 years.
IgM, C 3 )deposited subepithelially in the BM in a diffuse
global pattern.
Aetiology
Eighty-five per cent are idiopathic. Secondary causes Investigations
are shown in Table 6.10. Malignancies are an important Renal biopsy is required for diagnosis. Complement is
cause – being present in 5–10% of cases, particularly in normal (low levels in SLE-associated and hepatitis B-
older persons. associated MN).