I've watch a documentary about Marlie before, it's called 'Extraordinary People'.
https://www.youtube.com/watch?v=xk7yEj4g5YIVery interesting documentary to watch. Being born in Haiti where people still believe in curses etc, she and her family faced an extremely difficult time due to the enormous growth on Marlie's face, that lead the villagers in the area to think the family was cursed.
It was terrible for the family, and even worst for Marlie. Due to the growth, she refused to go out of her house and even had to quit school. It eventually became so heavy and painful that she had to support her head with her hands so that she can walk straight.
It was also her fortune that two Christian missionary nuns found out about her condition and help raised the funds and sent her for medical treatment overseas (as Haiti do not have a skilled consultant to offer the service). Now she have a new face and can lead a normal life.
It is no doubt, that as a Buddhist we believe in Karma. As the times we're in degenerate further, not so strangely we discover or new diseases (infectious, degenerative or genetic) surfaces. There are many diseases that we can classify as being imprisoned within our physical body. Take for example, spinocerebellar degeneration, a degenerative genetic disorder that causes all motor reflexes to degenerate in a short period of time from the time symptom occurs... causing the person to loose the ability to function physically but have a full functioning mental capacity. I think this is one of the most terrible disease... to be imprisoned within one's own body. Imagine, if you want to move your hand but you just could not move it no matter how hard you try.
However, despite all the karmic manifestations that we can see physically... I believe the worst of it would be one that interferes with our mental capabilities... the disease of the mind is far worst than any disease that can take place in us physically. Although one may be physically disabled, it is still possible to practice the Dharma as the Dharma is mind transformation and can be done even if one is on a wheel chair. But to be mentally 'off'... even if the person is physically able, he/she will not be able to practice the Dharma as they may be cognitively incapable to do so.
Therefore, to avoid from such karma manifestation, we must hold our vows and commitments clean. Not doing any harm to others would be a start. And because we have lived for countless of lifetimes, we should always do purification practices to purify the negative karma that we have collected for countless of aeons.