Vertex Pharmaceuticals Inc. said Friday that Ireland’s national health care system has agreed to pay for Kalydeco, a Vertex drug designed to treat some patients suffering from cystic fibrosis, a rare and often fatal genetic disease.

In a press release, Cambridge-based Vertex said that the Health Service Executive in the Republic of Ireland will fund Kalydeco for people ages 6 and older who have a specific mutation of the cystic fibrosis gene.

Several other national health services in Europe have taken a similar step, including health services in Germany, France, and England, Vertex said.

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Vertex received regulatory approval to market Kalydeco in the United States in January 2012. European regulators gave the drug their OK a few months later.

In the United States, it costs about $300,000 a year to treat a patient with Kalydeco, Vertex said.

Kalydeco targets the defective protein that causes cystic fibrosis and is the first medicine to treat the disease’s underlying causes, Vertex said.

Other cystic fibrosis drugs on the market only treat symptoms of the inherited disease, which causes mucus to thicken and block the passage of air to the lungs, making it harder for patients to breathe and digest food. Kalydeco targets the cause of the disease in roughly 4 percent of the US patient population of 30,000, previous Globe stories have noted.

Vertex also markets a drug called Incivek, a hepatitis C treatment.

Construction was recently started on a new company headquarters in Boston’s Seaport District. When the facility is ready, Vertex plans to relocate from Cambridge.