A crippled Kiseilian may not show a physical deficiency but it will surely have big problems to survive: it may suffer of cardiac syndromes, have difficulties to fly or walk, it may suffer of asthma or internal pain. Their lifes are not easy at all.
These Kiseilians cannot take part in some events and have -1 in each stat.
It could increase the chance to get sick more often on activities.
This mutation will not affect breeding as it's not inheritable but only a random inbred mutation.