Appearances are illusory. We cannot rely on physiological features to determine our karma.
This question is only resolved in meditation and the internal planes, because each person is a unique case. There are simply too many factors to take into account when understanding one's unique experience.
However, we can deduce that certain conditions, sicknesses, and illnesses are caused from specific behaviors which have been repeated for multiple lifetimes.
Other times, our diet, lifestyle, and habits shape our existence, not necessarily some ancient, hereditary karma we are unaware of.
In general, though, having a more or less strong and healthy body is definitely dharma, because we need a healthy vehicle by which to perform the great work.
Illness is the result of imbalance within the psyche, heart, mind, and body. Health is often the result of positive deeds, since "a healthy mind is a healthy body."
For thirty years I sought God. But when I looked carefully I found that in reality God was the seeker and I the sought. -Bayazid al-Bastami