People with psoriasis may be at an increased risk of developing chronic kidney disease, a new study indicates.

Psoriasis is a chronic, inflammatory skin condition that affects around 2% of the Irish population - some 100,000 people. It appears as pink or red raised patches on the skin. These patches, which are known as plaques, have a well-defined edge around them. They also have a scaly surface and can be large or small.

According to US scientists, there is increasing evidence linking the condition to diabetes and heart disease. However while a potential link between psoriasis and chronic kidney disease has been suggested, studies have so far been small with conflicting results.

The scientists decided to investigate this further by comparing the risk of chronic kidney disease in patients with and without the skin condition.

They used a UK medical records database to identify almost 144,000 adults with psoriasis. These were compared to over 689,000 patients without psoriasis. Known risk factors for chronic kidney disease, such as age, gender, high blood pressure and diabetes, were taken into account.

The study found that those with psoriasis, especially with severe forms of the disease, had an increased risk of developing moderate to chronic kidney disease compared with people who did not have psoriasis.

In fact, those with severe psoriasis were almost twice as likely to develop chronic kidney disease and were at least four times as likely to develop end stage kidney disease requiring dialysis.

The scientists from Philadelphia emphasised that even after they adjusted for known risk factors, severe psoriasis remained an independent risk factor for both chronic kidney disease and end stage disease requiring dialysis.

Meanwhile, a further analysis which compared over 8,700 people with psoriasis to more than 87,000 without the skin condition also showed that those with moderate to severe forms of psoriasis had an increased risk of developing chronic kidney disease.

The scientists explained that mild psoriasis is defined as limited disease - this is when 2% or less of the body's surface area is affected. Moderate psoriasis is known as scattered disease - 3-10% of the body is affected and severe or extensive disease refers to when more than 10% of the body is affected.

They noted that their findings suggest that while mild psoriasis does not appear to be linked to chronic kidney disease, moderate and chronic forms of the disease are. Around one in five people with psoriasis worldwide has moderate or severe forms of the disease.

The scientists recommended the close monitoring of people with moderate and severe forms of psoriasis for kidney problems.

"Future studies are warranted to confirm our findings, determine the mechanisms mediating renal insufficiency in psoriasis and examine the impact of treatment for psoriasis on the risk of chronic kidney disease," they added.

Details of these findings are published in the British Medical Journal.

For more information on psoriasis, see our Psoriasis Clinic here