Crown Princess Mette-Marit of Norway undergoing treatment for chronic condition

Crown Princess Mette-Marit of Norway will begin immediate treatment for a chronic condition she has been battling since 2018.

The Norwegian Royal House confirmed the news on Friday, explaining the royal's official engagements may be impacted.

"Previous experience has shown that the medicines can lead to side effects that can have consequences for the Crown Princess' official programme," the Royal House said in a statement that has been translated into English.

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"Therefore, we find it natural to share this information this time. We will inform you about changes to the official program if necessary," the statement continued.

Chronic pulmonary disease causes the tissue of the lungs to become damaged and can lead to breathing problems.

The disease is incurable, and worsens over time.

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Mette-Marit, 51, explained in 2018: "For a number of years, I have had health challenges on a regular basis, and now we know more about what is involved. The condition means that my working capacity will vary."

"The Crown Prince and I are choosing to make this public now partly because in future there will be a need to plan periods of time without an official programme to accommodate treatment and when the disease is more active."

The royal's doctor, Professor Kristian Bjøro at the National Hospital, said the progression of the royal's disease "has been slow."

Crown Princess Mette-Marit was a single mum when she began dating Crown Prince. The couple had previously met at a garden party in the late 1990s and reconnected later in life.

They married on August 25, 2001, at the Oslo Cathedral, becoming Her Royal Highness the Crown Princess of Norway. They celebrated their 23rd anniversary this year.

While their union was eventually accepted, it drew criticism early on due to here disadvantaged past and single mother status.

Since marrying the Crown Prince she has taken several university-level courses, obtaining a Masters degree in Executive Management in 2012.

Her son Marius is now 27. She and the Crown Prince have two children together – Princess Ingrid Alexandra, 20, and Prince Sverre Magnus, 19.

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The royal couple's most recent appearance was a country tour to Selbu Malvik, Midtre Gauldan and Trondheim in Norway on September 11.

This included a stop by Solberg Farm and a visit to a local hospital. The royals were greeted by supporters waving the country's flags.

They also visited Gausdal Secondary School and met with pre-med students.

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