In a lounge, Cameron is explaining that cocaine or meth "are very hard on the blood system" and could cause Larry's symptoms, and Larry's dad doesn't think it's drugs, but -- and the camera swings over to Fishface, sulking on a couch out of earshot -- he does know that Fishface "was in rehab in the ninth grade." Blah blah blah fishcakes (...sorry), Dad doesn't approve of Fishface and thinks she only cared about the car, not about Larry, but Fishface is pretty much a red herring (...sorry!) here, so let's move on to the part where we find out that Larry's mom died of cancer. Cameron tells Dad they're going to test Larry for drugs. By now, he's gotten a "real" name, "Keith," but I'm used to typing "Larry" now, so Larry he shall remain.
"I don't do drugs," Larry is protesting. Chase: "It's not that we don't trust you, but...[doink!]" He plucks one of Larry's hairs as Cameron VO explains to Dad that the hair will tell them what drugs, if any, Larry has taken in the last sixty days, "kind of like...rings on a tree." Chase loads the vial into the test machine, then checks the results screen. He's galled to admit it, especially since Foreman is eyeing him smugly, but it's negative for drugs, so it's Mystery Ailment 1, Chase's Diagnosis 0.
Back to Cameron questioning Dad about travel, and how he himself is feeling lately, and Dad tells her he feels fine, and they went to China but got all their shots first. Cameron says they'll test for an infection, just in case, and Larry is on what looks like an open MRI table while Foreman looks at the radioimmunoassay monitor in the next room. Given that Foreman is sort of grinding his knuckles while making a "...dammit" face, we can assume it's Mystery Ailment 1, Foreman's Diagnosis 0...
...a conclusion borne out by the fact that Cameron is now asking about joint pain and whether anyone in the family has been diagnosed with lupus. Dad doesn't even know what that is, which lets Cameron exposition that "in simple terms, the body becomes allergic to itself," which I thought we all knew because Richard Dreyfuss's wife did those PSAs about it years ago, but okay. Dad, overwhelmed, fidgets with a hand over his mouth while Cameron explains more about lupus, then asks if it's treatable. "It...can be manageable," Cameron says carefully, adding that they'll test for an antibody which 95 percent of lupus patients have. Cut to the lab, and Foreman and Chase discovering that Larry does not have said antibody. Mystery Ailment 1, Cameron's Diagnosis 0, for an overall score of Mystery Ailment 3, the Houselings 0.