Portrait of a(n) (ill?) Young Man

Can doctors spot illness in centuries-old paintings? Some friends and I (none of us experts when it comes to the visual arts) were talking about the significance of the subject's hand gesture in Botticelli's painting Portrait of a Young Man the other day, so I looked it up online. I found this paper from a 1983 issue of the journal Arthritis and Rheumatism. The article claims that the swelling in the joints of the hand is characteristic of juvenile rheumatoid arthritis, and that the painting may document one of the earliest cases of the illness. The authors base their claims on their studies of Botticelli's other works, concluding that the swelling is not a stylistic trait, nor is it a mistake, as Botticelli is well known for his superb technique.

As for the actual positioning of the fingers, the paper notes that the third and fourth finger were often painted together for aesthetic reasons by many artists of the Renaissance, and the fifth finger was often bent as well. (The Wikipedia article is a bit misleading on this subject, as its wording suggests the hand gesture itself is considered to be a symptom of arthritis.) For example, a similar gesture can be seen in the left hand of the subject of Botticelli's painting Fortitude, which represents one of the seven virtues:
The 1983 paper reminded me of a recent claim made by pathologist Vito Franco of University of Palermo that an examination of Mona Lisa's face indicates she had high cholesterol when she was painted. Franco has studied other paintings of the Renaissance and made several other conclusions about illnesses afflicting the subjects. (Unfortunately, I couldn't find a link to his formal findings, which he presented at a human pathology conference in Florence last fall.)

In going back to the Time article on these claims, I found that Franco actually has a different diagnosis for Botticelli's Young Man. According to him, the subject suffers from Marfan syndrome, a genetic disorder that affects connective tissue and generally results in tallness and elongation of limbs. As evidence, Franco presents the "unusually long, thin fingers" of the young man.

Personally, I am skeptical of diagnoses of diseases based on analysis of paintings of patients, but I think it's fascinating that beloved art can be approached from all sorts of angles, even medical ones.