Genzyme (NASDAQ:GENZ) is sitting on cruise control for the moment, but it should be able to step on the gas just as soon as regulators in the U.S. and Europe allow it.

The company expects this quarter's adjusted earnings to be flat compared with the previous quarter's $1.04 per share. That would be a 9% increase year over year, but Genzyme is a high-growth company where quarter-over-quarter measurements are important.

The flat growth of earnings is coming from supply constraints from Myozyme, its treatment for a rare disorder called Pompe. Genzyme is guiding for 50% sales growth this year, but first it has to get American and European regulators to sign off on larger manufacturing scales. It's expecting a decision by Feb. 28 from the Food and Drug Administration and in April from the European regulators.

Once it does step on the gas, investors should get a nice ride in the form of 13% to 17% revenue growth this year. That's pretty impressive, considering that it's having to fight through a major headwind from currency movements just like its large pharmaceutical counterparts, Johnson & Johnson (NYSE:JNJ), Bristol-Myers Squibb (NYSE:BMY), and others.

Genzyme, BioMarin Pharmaceuticals (NASDAQ:BMRN), Regeneron Pharmaceuticals (NASDAQ:REGN), and the other orphan-drug specialists have shown that there's plenty of growth available in selling drugs for rare diseases. With a well-stocked pipeline -- partially thanks to licensing drugs from Isis Pharmaceuticals (NASDAQ:ISIS) and Osiris Therapeutics (NASDAQ:OSIR) and nice cash flow -- the growth at Genzyme should continue into the future.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. Johnson & Johnson is a selection of the Income Investor newsletter. The Fool has a disclosure policy.