GUILDERLAND — On Sept. 20, two Guilderland freshmen each swam one mile across the 62-degree waters of the Boston Harbor to raise awareness of a disease plaguing one of the boy’s stepfather and four-year-old sister.

When Michael Ardito found out his younger sister, Kati Harrington, was diagnosed with hereditary angioedema (HAE), he immediately wanted to do something. He had seen the effects of the disease on his stepfather, John Harrington, and didn’t want his little sister to have to endure the same thing.

The hereditary disease causes swelling in the hands, feet, throat, and face, and the swelling can become fatal if it closes the airway.

Michael saw his stepfather go into a coma lasting over three days because of swelling in his throat.

The disease often goes misdiagnosed as allergies, Michael said, and also has many of the same symptoms as spider bites.

EpiPens have no effect on HAE symptoms, he continued.

“It was pretty devastating” to find out his sister had the disease, Michael said. That devastation turned to ambition, and Michael and his family held a family triathlon in 2010 to start raising awareness of the disease and money to find a cure.

This August, Michael and his family started a fundraising website where people could donate to the cause, and tied it to the swim across the Boston Harbor.

The boys swam during Boston Sharkfest, an annual open-water swim event that caps at 800 participants.

The fundraising page the family made is called “Taking a bite out of HAE,” and raised $8,640, over $3,000 more than its original goal.

“The awareness that page has brought in,” Michael said, “is better than the money.”

For the swim, Michael’s friend Luke Tanner joined him.

“He was the only one I knew, without question, that would do this,” Michael said.

The two boys have been swimming together for five to six years, and Michael is currently on the Guilderville varsity swim team; Luke is a triathlete.

Asked about the swim, Michael said, “It was definitely cold. A lot colder than I thought it would be.”

He also said it was “very motivating” to think about all the people supporting him and Luke.

“It was a shock to see that many people cheering for us,” he said. “It was kind of insane.”

“I want this to kickstart fundraising for the future,” he continued.

All the money his fundraising earned will go to HAEA, the U.S. Hereditary Angioedema Association, toward finding a cure for the disease, which affects about one in 10,000 to one in 50,000 people.

While a blood test at any age can look for common indicators of HAE, symptoms usually don’t manifest until the teenage years.

Triggers for an attack include anxiety, stress, and illness, but attacks can also occur spontaneously, with no known trigger.

While Michael and his family don’t have any concrete plans for future fundraising events, ideas are in the works.

“I know definitely next summer we will be doing more,” he said.