June 15 (Reuters) - Sarepta Therapeutics SRPT.O on Sunday said there had been a second reported case of acute liver failure resulting in death after a patient received the company's gene therapy for a rare form of muscular dystrophy.

Sarepta shares slumped 20% in overnight trading.

The patient was undergoing treatment with Sarepta's therapy called Elevidys, which is the only gene therapy approved by the U.S. Food and Drug Administration for Duchenne muscular dystrophy patients aged four and above.

The first instance of death was reported in March this year, a 16-year-old boy who died from acute liver failure months after receiving Elevidys.

Liver damage is a known risk with Elevidys and other gene therapies that use adeno-associated viral vectors to infuse modified genes.

Sarepta said it is taking steps to mitigate the risk of acute liver failure in patients by working to convene an independent group of experts in Duchenne and liver health to consider an enhanced immunosuppression regimen for Elevidys. The company also said it has suspended shipments of the therapy for patients unable to walk and informed the FDA and global health authorities about the incident.

Roche ROG.S, which partners with Sarepta for commercialization of the gene therapy outside the United States, said in a separate statement on Sunday that it has paused the dosing of Elevidys in patients who are unable to walk following the two cases of fatal acute liver failure.