By the time he reached Los Angeles, Landry was scared, dazed and exhausted. Flying for the first time in his life, the 13-year-old from Cameroon was now some 8,200 miles from all things familiar.

Landry, whose parents had recently died in a car crash, came to LA to live with his legal guardian. Although Aunt Delphine welcomed him warmly, Landry’s first night in America was restless. His left ankle was puffy and warm.

He settled in to his new environment, attending school and studying English while speaking French and Cameroonian pidgin at home. He played soccer and watched YouTube videos on his cellphone. But his ankle and lower leg continued to swell on occasion.

“In the hospital where I work,” Delphine, a certified nursing assistant, told Landry, “elderly people can have blood clots that make their limbs swell. But in someone your age, that doesn’t make sense. The next time this funny thing happens, please tell me tout suite, and I’ll take you to a clinic.”

Sure enough, Landry’s symptoms returned, and Delphine cajoled a local doctor into ordering an MRI of her nephew’s leg. But the swelling was gone by the time the scan was performed.