Membranoproliferative glomerulonephritis (MPGN): a rare kidney filter disease

The NHS describes glomerulonephritis as damage to the tiny filters inside the kidneys, the glomeruli, often caused by the immune system attacking healthy body tissue. MPGN is one particular pattern of this damage. Kidney Care UK explains that it occurs when antibodies and/or a part of the immune system called complement are deposited in the kidneys, which affects the kidneys' ability to filter the blood and can eventually lead to a reduction in kidney function.

MPGN is also sometimes called mesangiocapillary glomerulonephritis (MCGN). Kidney Care UK says there is a specific subtype of MPGN called C3 glomerulopathy (C3G), and a specific subtype of C3G called dense deposit disease (DDD). The precise diagnosis depends on the location and appearance of the antibody and/or complement deposits within the kidneys.

Because it is rare, MPGN is usually looked after by a specialist kidney (nephrology) team rather than in general practice alone.

Kidney Care UK says some people have no symptoms. When symptoms occur, they include blood in the urine, which may look red or dark brown like a cola drink, is more likely to be noticed after an infection such as a cold or sore throat, and is painless. The blood may be visible only under a microscope. Kidney Care UK adds that the amount of blood is not an indication of severity.

Protein in the urine is another feature; if there is a lot, the urine may look frothy, and the more protein there is, the more severe the condition is. Swelling or puffiness (oedema) may develop, especially around the eyes and ankles, and is caused by the kidneys retaining too much water. High blood pressure and mild or moderate anaemia can also occur.

The NHS lists other possible features of glomerulonephritis, depending on cause, including rashes, joint pain, stomach pain, high temperature, shortness of breath, jaundice, peeing a lot less than usual, tiredness, and loss of appetite and weight loss.

The NHS says that if a GP suspects glomerulonephritis they will usually arrange blood tests to check protein and creatinine and a urine test for blood or protein, and that further tests may include an ultrasound scan and a biopsy. The NHS describes a biopsy as removing a small sample of kidney tissue, carried out using local anaesthetic, with an ultrasound machine used to locate the kidneys.

Kidney Care UK says MPGN is diagnosed by kidney biopsy. Under the microscope, antibodies and/or complement can be seen in the kidney's cells. Blood tests can check complement levels and genetic testing may be offered.

The NHS advises seeing a GP if you notice blood in your urine, which does not always mean glomerulonephritis but should be investigated, or if you have other symptoms such as joint pain, tiredness and shortness of breath.

Kidney Care UK says MPGN occurs due to a fault in the immune system that causes antibodies and complement to be deposited in the kidneys, and that it is not currently known why this happens. It usually follows other medical problems such as chronic infection like hepatitis or autoimmune conditions like lupus, which is called secondary MPGN. When no cause can be found, it is called primary or idiopathic MPGN.

On inheritance, Kidney Care UK says there is some recent research that MPGN may run in families, but the precise details of any inheritance patterns are still being investigated. The NHS says that if you are diagnosed with an inherited type of glomerulonephritis, a doctor can advise about the chances of someone else in the family being affected.

Treatment for secondary MPGN focuses on the underlying disease, according to Kidney Care UK. For primary MPGN, treatment focuses on reducing blood pressure with ACE inhibitors or ARBs, which also reduce the loss of protein in the urine, slowing progress and preventing or at least delaying further kidney damage. Immunosuppressants such as steroids may be prescribed to help control the immune system. Dietary changes, including a low-salt diet to reduce swelling, may be recommended, and a diuretic may be prescribed.

Kidney Care UK advises that any dietary changes should only be made with advice from a specialist kidney dietitian, and that vitamin D supplements may be recommended if kidney function continues to decline. Dialysis and/or transplant may be needed if kidney damage becomes severe, and MPGN can reoccur in a transplanted kidney.

On outlook, Kidney Care UK says that although some people have a spontaneous remission, in most cases the condition remains active, and half of all people with MPGN will develop kidney failure within 10 years. The NHS notes that complications of glomerulonephritis can include high blood pressure, high cholesterol, blood clots, damage to other organs, chronic kidney disease and kidney failure, and that a doctor may prescribe medicine to help lower blood pressure, lower cholesterol or protect against blood clots.

Kidney Care UK points people to the MPGN/DDD Support Group for more information about diagnosis, symptoms and treatment. Given the long-term nature of the condition, regular monitoring of blood pressure, urine protein and kidney function is part of care, and it is worth asking your kidney team how often you will be reviewed.