There was supposed to be a special party for Kendric Cromer, 12, last Wednesday, but it had to be postponed because he was too groggy to celebrate.

It was meant to mark the first day of his new life — the day he became one of the first children ever to be treated with a newly approved gene therapy that will free him from the sickle cell disease that has stolen his childhood.

On Sept. 11, despite the excitement of the moment, Kendric was unable to keep his eyes open as he lay in his hospital bed at Children’s National Hospital in Washington because of the drugs he had been given in preparation for his treatment.

His life with the disease has been punctuated by episodes of excruciating pain, requiring days in the hospital as doctors tried to control it. Sickle cell eroded his hip bones. It prevented him from riding a bike or playing soccer or even going outside when the temperature was below 55 degrees Fahrenheit because cold often brought on intense pain.

Now he could see a future — in a month or so — without pain from sickle cell.

“I can’t wait to start my new life,” he told his mother, Deborah Cromer.

His disease is caused by an inherited genetic mutation that leads to blood cells that form crescent shapes — sickles — instead of discs. Trapped in blood vessels and organs, the cells cause damage and pain. Gene therapy fixes that problem by giving the patient a new, normal hemoglobin gene.