McKusick's belief in this paradigm-the focus on disability rather than abnormalcy-was actualized in the treatment of patients in his clinic. Patients with dwarfism, for instance, were treated by an interdisciplinary team of genetic counselors, neurologists, orthopedic surgeons, nurses, and psychiatrists trained to focus on specific disabilities of persons with short stature. Surgical interventions were reserved to correct specific deformities as they arose. The goal was not to restore normalcy-but vitality, joy, and function. McKusic had rediscovered the founding principles of modern genetics in the realm of human pathology. In humans as in wild flies, genetic variations abounded. Here too genetic variants, environments, and gene-environment interactions ultimately collaborated to cause phenotypes-except in this case, the phenotype in question was disease. Here too some genes had partial penetrance and widely variable expressivity. One gene could cause many diseases, and one disease could be caused by many genes. And here too fitness could not be judged in absolutes. Rather the lack of fitness-illness [italicized, sic] in colloquial terms- was defined by the relative mismatch between an organism and environment.
~ Siddhartha Mukherjee
