Nail clubbing. Cause for the conditions?

Hello, I noticed I have clubbing about 2 years ago and consulted a doctor. The doctor has recommended for an ECG test and chest X-ray. The results were completely normal at that time. Doctor said its an early stage of clubbing and told me that, I should not neglect it. More or less from the same time I'm suffering from alopecia areata. I have suffered from alopecia areata in my childhood but it was there for only few months whereas now the problem is still present after 2 years. Does alopecia areata and clubbing relate to each other in any way? Does these conditions mean that I'm suffering from any major disease? Also please suggest what should I do now in order to find out the cause for the conditions? Many thanks.