He's 25, now and has a second bullseye on his leg. He'll be going to the doctor this afternoon.

Any information about dealing with the disease and side-effects would be appreciated.

Most of us do not have medical backgrounds, but we have had to learn a lot about Lyme & other Tick-Borne Diseases (TBDs).
The info we share is from experiencing these illnesses.

Since your brother had a misdiagnosis for about a month, had such a "bad" case of Lyme, & still has symptoms, it sounds as if he could have the original case & it's flaring up, maybe triggered by a new tick bite.
This would mean that the "side effects" are really symptoms of Lyme.

Also, a new tick bite may have caused the bull's eye rash. Either way, the EM rash (Erythema Migrans - bull's eye rash) is diagnostic for Lyme disease.

Do you know anything about the treatment he received when he was 16?
...antibiotic?
...dose per day?
...length of time treated?

Since he has continued to feel "the effects of the disease", I'd recommend that he be seen by a Lyme Literate Med Dr (LLMD).
There are not many available, so usually the majority of their patients have Lyme and/or Co-Infections, which means they have a lot of experience.

Go to "Seeking a Dr" here on LymeNet and put your location in the title.
Drs' names are not given here without their permission, so info on LLMDs will be
e-mailed to you.

If your brother's dr is recommended, then that is great.
If not, then in my opinion, it would be wise to have an evaluation done by a LLMD.

You don't mention how long your brother was treated for his first infection. My guess is 4-6 weeks of doxycycline and he was "cured." The reason I say this is if he really was cured, he would not have any continuing symptoms. So, the bull's eye rash could be an old infection or another one on top of the old infection.

Note that the rash makes it so that he absolutely has Lyme. No tests are necessary in order to start treatment.

The links that treepatrol posted are all good. There is an awful lot of new information that we have on Lyme Disease and the coinfections that may come with it.

The doctors who have been treating it a lot are called Lyme Literate Medical Doctors (LLMD) and your brother should find one right away.

There are many doctors out there who don't have the latest information for many reasons - mostly having to do with money.

As you learn more, you'll start to understand what I'm talking about. Dig in. There's lots to learn.

Good Luck,