History and exam
Key diagnostic factors
common
presence of risk factors
Hx of autoimmune diseases, hepatitis B or C, syphilis, malignancy, and use of medications such as non-steroidal anti-inflammatory drugs (NSAIDs), gold, penicillamine, lithium, or captopril.
oedema
Typically generalised, including the lower extremities and peri-orbital regions.
elevated BP
Can be due to increased salt retention and volume overload, or due to renal dysfunction with decreased glomerular filtration rate.
Other diagnostic factors
common
incidental proteinuria or abnormal renal function
Patients may present after being referred with the incidental finding of proteinuria or abnormal renal function.
xanthelasma
Commonly seen owing to resulting hypercholesterolaemia.
foamy urine
May be caused by increased protein in the urine.
uncommon
fatigue/malaise
Non-specific symptom that may indicate an underlying secondary cause.
anorexia
Non-specific symptom that may indicate an underlying secondary cause.
Muehrcke's lines
White lines of the nails due to hypoalbuminaemia.
Risk factors
strong
male sex
Male to female ratio is 2:1.[2]
age >40 years
HLA-DR3
Associated with a higher risk of MN.[11]
autoimmune disease
hepatitis B and C
syphilis
Now a rare cause, but circulating antigen-antibody complexes can be deposited in the sub-epithelial space, leading to MN.
solid organ carcinoma
Lung and colorectal (most common) carcinomas may lead to tumour antigen deposition on the sub-epithelial surface and complement activation.[15]
medications
Uses of non-steroidal anti-inflammatory drugs (NSAIDs), gold, penicillamine, lithium, and captopril have been implicated as causes.[1][16] The mechanism associated with drug-induced MN is not clear. Proteinuria generally develops within the first 6 to 12 months of drug treatment, but can occur as late as 3 to 4 years. Discontinuation of the drug leads to resolution of the proteinuria in virtually all cases.
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