Updated from 10:33 a.m. EST

European regulators have recommended rationing of a

Genzyme

( GENZ) drug to treat a rare genetic disorder due to unspecified manufacturing problems.

The European Medicines Agency (EMEA) said Friday that infants, children and adolescents with Pompe disease should be given priority access to Genzyme's Myozyme due to a supply shortage that is expected to last several months.

The EMEA said the Myozyme shortage was caused by an increase in demand for the drug as well as unspecified manufacturing problems at some sites where Genzyme makes the drug.

Last week, Genzyme pre-announced fourth-quarter Myozyme sales of $75 million but also warned that supplies of the drug would be tight between January and April of this year due to manufacturing constraints.

Deutsche Bank biotech analyst Mark Schoenebaum, in a note to clients Tuesday morning, said the new Myozyme manufacturing issues disclosed by the EMEA Friday could reduce Myozyme to equal or below fourth-quarter 2008 levels. Presently, the consensus estimate for Myozyme first-quarter sales is $91 million, according to Schoenebaum.

"The EPS

earnings per share impact should be modest given Genzyme's ability to manage expenses," he added. Schoenebaum has a hold rating on Genzyme.

Genzyme is in the process of seeking regulatory approval for two new manufacturing plants to produce Myozyme. A U.S. plant is expected to receive FDA approval in February. A larger facility in Belgium is under review by European regulators with a decision expected in April.

Myozyme sales in 2008 reached $296 million compared with sales of $201 million in 2007.

Pompe disease is a rare genetic disorder in which patients lack an enzyme to break down glycogen, which builds up in certain tissues like the heart and muscles and can lead to heart problems, breathing difficulties and muscle weakness. When Pompe disease occurs early in life, it can progress quickly and is usually fatal without treatment.

Genzyme is currently the only drug maker to market a treatment for Pompe disease, although

Amicus Therapeutics

(FOLD) - Get Report

is developing its own drug, currently in phase II studies. Other companies which make and market drugs for rare genetic diseases include

Shire

( SHPGY)

Genzyme shares were up 0.8% to $68.23 heading into Tuesday's close.

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