Why are we all so different? The plain answer is genetic polymorphisms. Perhaps the best known example is sickle cell anemia. Most people have hemoglobin A, but an unlucky few have a polymorphism at position 6 of the beta chain of hemoglobin so that what would normally be a glutamic acid is replaced by a different amino acid, valine. The effect of this is that under certain stressful conditions, the hemoglobin molecules line up as needle like crystals that distort the shape of the red cells so that they can't get through the narrow holes in the blood vessels and therefore cause ischemia in organs supplied by those blood vessels.
But sickle cell anemia is just the most severe of hundreds of polymorphisms of the hemoglobin molecule. Some cause anemia but many are entirely asymptomatic and people have no idea that they have them. So it is for just about every molecule in the body, but together they determine our every physical characteristic.
I have written about CD38 several times before. CD38 also has a polymorphism characterised by a C>G variation in the regulatory region of intron 1. A study from the excellent group in Turin, Italy has studies 248 patients with CLL, but find that this polymorphism is no commoner in patients than in controls. However, those with the polymorphism were more likely to have bad prognostic markers, more likely to have enlarged lymph nodes and spleen, and in particular, more likely to develop Richter's syndrome.