Found this article (abridged here) by Doug Caldwell, "Fire in His Fingers". Thought it might be of interest to some: first detailed discussion I have ever found (for those with an interest in the macabre):

"December 2, 1928, an 18 year old Django Reinhardt had just finished at a club called La Java. It was 1:00 a.m. He trudged back to his caravan home where his wife, a few months pregnant, was sleeping. The wooden wagon on this night was full of colourful cellophane flowers that his wife was to sell at a cemetery next day. While getting undressed, Django thought he heard a mouse rustling around in the flowers, and as he grabbed a dying candle to have a look, the wick separated from the wax, and fell into the mass of explosive cellophane. Within a millisecond, the caravan was an inferno. Django just managed to grab a blanket with his left hand to shield himself, exposing the hand to the flames. He fell down, almost unconscious; his wife scrambling out of the burning caravan, her hair almost completely scorched. After long moments, he staggered to his feet, and stumbled out of the caravan. His left leg was burned so badly that it was urged that it be amputated, but after two operations, it was saved. He spent a year and a half in hospital. Even into the 1940's he was healing from sores, bathing and pouring sulfur into his wounds.

His ring and little fingers were all but useless, muscles and tendons destroyed. They remained curled up, leaving him only the index, middle, and thumb to chord with. To compensate, he developed a technique of crossing the first finger over the second and vice versa. We do know from musicians' accounts that he was able to pull the two dead fingers onto the high B and E strings for chordal work, and was able to bend the third finger enough to flatten it across the three bottom strings."