Genzyme has sent a letter to U.S. patients of its enzyme replacement therapies of rare diseases, letting them know that they will be receiving more doses of medicine than they have for the past year during the company’s scaled-back operations stemming from a temporary shutdown of its Allston manufacturing plant in June 2009.

American patients taking Cerezyme for Gaucher disease will be able to return to their full bi-weekly dosing schedule. The letter also stated that doctors can now submit requests from new patients who want to start taking Cerezyme.

Those patients taking Fabrazyme for Fabry disease were notified that they would receive one dose per month for September and October – roughly half their normal dose, but up from the every other month dosing schedule Genzyme has had to impose since its temporary shutdown. The company is not able to accommodate any new Fabrazyme patients at this time.

This is a welcome piece of good news from the Genzyme manufacturing front, as it has sought to emerge from a series of setbacks, including the discovery of foreign materials in their drugs in November, a water system problem that forced them to discard some drugs in March, and a serious enforcement action levied by the U.S. Food and Drug Administration in April.

The news is well-timed, as Genzyme reportedly seeks to increase the asking price of the company, in a potential buyout deal with Sanofi Aventis.

Genzyme officials did not post the patient letter on its “supply update” website, or submit it to the FDA, unlike previous letters to patients, because they said they wanted to be cautious and avoid letting patients down. The improved dosing schedule only applies to U.S. patients.