What: bluebird bio (NASDAQ:BLUE) was down as much as 12% Tuesday, apparently on no news. The stock just started falling from the open and never really recovered.

So what: Let's keep this in perspective. Bluebird bio traded this low as recently as last Tuesday. Then shares traded up for a few days in anticipation of the release of abstracts at American Academy of Neurology on Thursday.

Investors seemed to like the limited data in the abstract for bluebird bio's phase 2/3 Starbeam study testing its Lenti-D gene therapy for the treatment of cerebral adrenoleukodystrophy. The clinical trial won't finish until patients have been followed for two years after treatment, but the interim data showed no major functional disabilities -- the primary endpoint of the study -- in the 12 patients that have been followed for at least six months since they were treated with the Lenti-D gene therapy.

As things often happen, short-minded investors soon remember that that we're only about a quarter of the way through the two-year study and sell the news. We could see another bump -- and potentially another decline -- later this month when the company presents at the meeting on April 20. Abstracts for scientific meetings have to be submitted well before the meeting, so the data at the meeting is likely to be more up to date than the abstract data.

Now what: Long-term investors don't really need to worry about the daily stock price change. Changes last week and today will have very little effect on the stock price when the Starbeam study finally reads out.

And keep in mind, while it would be great to treat cerebral adrenoleukodystrophy, bluebird bio's LentiGlobin gene therapy for treating beta-thalassemia and severe sickle cell disease is arguably more important than the Lenti-D program. We'll have to wait until the American Society of Hematology in December for the next major update on the LentiGlobin program.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.