If your child is found disabled because of a deformity in one hand that is currently severely disabling, you would also need to report once the child learns to compensate for the limitations, and he will learn to compensate.
Quoting this, because I think it's an especially important point.
Children with congenital limb deficiencies do learn to compensate, and often excel, despite their differences.
My daughter was born with symbrachydactyly. She has a partial thumb and no other fingers on her right hand (which would have been her dominant hand). This has presented challenges for her, to be sure. But anyone who has seen her in action would be hard pressed to label her
disabled.
There is the story of Pete Gray, the man with one arm who became a minor league baseball player. He learned to compensate.
Jim Abbott was a two-sport athlete in high school, became the first U.S. pitcher to beat Cuba
in Cuba in 25 years, threw a complete game en route to an Olympic gold medal, was a 1st round draft pick by the Angels, won his first professional game without playing a single day in the minors, and hurled a no-hitter for the Yankees. All with one hand.
It is highly possible that with the right therapy and practice and modifications, your child could live a thriving life with a deformed hand. Attitude and perseverance will determine how successful he will be. The deformed hand is just a small piece.
Paul Wittgenstein was a rising concert pianist when he was called up into military service during WWI. He took a bullet in the elbow, became a prisoner of war, and lost his right arm to amputation. After the war, he continued his career one handed, playing pieces composed especially for him by the likes of Prokofiev, Strauss, and Ravel.
Best wishes to you and your son, 01ajp2012.