A pilot, whether sport, recreational, private, commercial, or airline transport of whatever rating, would have a serious time justifying flying with a *disqualifying* condition.
But there are very few permanently disqualifying conditions. For instance if a pilot's blood pressure is greater than 155 (Systolic) or greater than 95 (Diastolic), then he is disqualified from flying. With diet, exercise, or medication, the flying priveleges can be restored once the high blood pressure is reduced. (Most blood pressure medications are not disqualifying.)
What medical conditions does the FAA consider disqualifying? The following conditions are listed in the regulations as disqualifying medical conditions;
however, in many cases when the condition is adequately controlled, the FAA will issue medical certification contingent on periodic reports.Angina pectoris
Bipolar disease
Cardiac valve replacement
Coronary heart disease that has been treated or, if untreated, that has been symptomatic or clinically significant
Diabetes mellitus requiring hypoglycemic medications
Disturbance of consciousness without satisfactory explanation of cause
Epilepsy
Heart replacement
Myocardial infarction
Permanent cardiac pacemaker
Personality disorder that is severe enough to have repeatedly manifested itself by overt acts
Psychosis
Substance abuse
Substance dependence
Transient loss of control of nervous system function(s) without satisfactory explanation of cause.
Here's the website where I found the above conditions:
http://www.faa.gov/licenses_certificates/medical_certification/faq/response6/ For recreational on up, it is an FAA certified aviation medical examiner (AME) and the FAA that makes the determination that a disqualifying condition has been brought under control.
For light sport pilot . . .