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Shares of Illumina (ILMN - Get Report) plunged more than 16% on Friday after the genome-sequencing biotech company lowered its second-quarter revenue expectations amid a deferred sale of at least one its gene-sequencing machine systems.

The San Diego-based company on Thursday provided updated revenue guidance for the quarter ended June 30, of $835 million, compared with $830 million a year earlier. Analysts polled by FactSet were expecting revenue of $888 million.

Some $30 million of the revenue hit was due to one sale that didn't close as expected in the second half of June, the company said. That transaction is still expected to close later in 2019.

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"We are obviously disappointed with our second-quarter financial results," CEO Francis deSouza said in a statement. "Our preliminary analysis suggests that these challenges are transitory and do not reflect a macro change to the fundamentals of our business. 

Illumina also lowered its outlook for the year, saying it now expects revenue growth of 6%, compared with its previous guidance of 13% to 14%. 

Shares of Illumina were down 16.07%, or $58.45, to $305.21 in Friday trading on the Nasdaq Stock Market. The shares ended the day Thursday down 2.43% at $363.66.

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