NYPD detectives are investigating the mysterious death of a 19-year-old Staten Island man found in his family’s home with suspicious injuries Tuesday, police said.

When EMS arrived at the home on Elmwood Park Drive near Devon Loop in New Springville shortly after 11 a.m., they found the teen victim dead in the living room.

He had bruising on his wrists, swollen ankles, and his ribs were protruding from his skin, as if he was malnourished, a police source with knowledge of the case said.

The victim’s mother said she heard a loud thud before finding her son dead on the floor, but the teen’s injuries weren’t consistent with a fall, a second police source said.

As police continue to investigate, an autopsy has been slated to determine how the teen died, officials said.

A man at the home who introduced himself as the dead teen’s stepfather told a Daily News reporter that there was “nothing to be concerned about.”

“(The police) are here as a precaution,” the stepfather said.