A class-action lawsuit has been filed against the health insurer Aetna for a July 28 mailing that may have exposed the HIV status of approximately 12,000 recipients through the envelope window, per STAT.

The AIDS Law Project of Pennsylvania filed the suit with the Legal Action Center and Berger & Montague P.C. on behalf of the plaintiff, described as a "52-year-old Bucks County [Pa.] man, whose sister learned from an unopened large-window envelope that arrived in their mail that he was taking HIV medications."

Aetna's response: The company didn't comment on the lawsuit, but it apologized for the privacy breach last week and said it was "undertaking a full review of our processes to ensure something like this never happens again."

Why it matters: Health care companies and providers are legally required to protect patients' medical privacy, as Aetna itself acknowledges.