Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Aegerion Pharmaceuticals (NASDAQ: AEGR), a biopharmaceutical company focused on therapies to treat rare and unmet diseases, dipped as much as 14% after reporting its preliminary 2013 and 2014 sales guidance and disclosing a Department of Justice subpoena over the marketing of lead drug, Juxtapid, after the closing bell last night.

So what: According to Aegerion's press release, it anticipates reporting preliminary 2013 net product sales of $48 million to $49 million and estimates 2014 sales will be in the range of $190 million to $210 million. By comparison, Wall Street had forecasted $49.8 million in sales in 2013 and $204.2 million in 2014. The real downer today, though, is the announcement that the DOJ is requesting documents related to the marketing of its homozygous familial hypercholesterolemia drug, Juxtapid. Aegerion announced that it intends to cooperate fully with the investigation.

Now what: Although sales estimates for 2013 came in a bit lighter than estimates, the concern with investors is solely over the marketing subpoena. The problem with this subpoena is twofold. First, these investigations can go on for weeks or months, placing a cloud of uncertainty around Aegerion's share price and potentially capping any near-term gains. Second, there's the possibility that, if any wrongdoing were discovered, it could result in fines. Obviously, there have been plenty of investigations from the DOJ that have resulted in no wrongdoing or just a slap on the wrist, but some do indeed result in fines. I was already concerned about Juxtapid's high price point and sales potential relative to the competing HoFH treatment on the marketplace, Kynamro, from Isis Pharmaceuticals and Sanofi, so today's news gives me even more recourse to avoid the company in the meantime.