I received a letter like this after my son broke his arm, about 3 years ago. It was from a Florida law firm.
They sent me a 10-page questionnaire, essentially asking for my son's entire medical history, as well as personal details about our family.
I threw several of them away. Then they called me. I got their address and wrote them a letter. I told them to forward to me:
1. The agreement establishing attorney-client privilege with their firm and my employer and/or my insurance carrier, to include any confidentiality agreements;
2. The document where I agreed to the sharing of personal information with outside entities as a condition of my employment and/or insurance coverage;
3. The justification for requiring my son's entire medical history.
I never heard back from them.