The Argentine pope was ending his weekly audience in St Peter's Square on Wednesday when he turned his attention to the man, who suffers from neurofibromatosis, an illness which causes tumours all over the body.
Images of Francis kissing and hugging the man quickly circulated the world, furthering his rapidly growing reputation as "the people's pope" and winning praise from commentators for his compassion
Francis, whose real name is Jorge Bergoglio, was known in his former role as the Archbishop of Buenos Aires for his concern for social issues and preference for a modest lifestyle. He was famed for shunning the archbishop's lavish residence in the Argentine capital, instead living in a simple apartment, cooking his own meals and using public transportation.
The newest occupant of St Peter's Chair comes from the Jesuit school of Catholicism, which has a strong focus on social justice. Since entering the Vatican, Francis has displayed a more open and inclusive attitude on social issues than many of his predecessors. He has won praise from sectors formally marginalised by the Catholic Church, such as divorced couples and gay people, whose numbers are reportedly increasing in congregations under his watch.
On several occasions members of his flock have been surprised to receive phone calls from Francis himself after writing him letters detailing painful life experiences. In one reported case, Francis personally telephoned Michele Ferri of the Italian city of Pesaro, to offer words of comfort after the man wrote to him about his struggles with his faith following the murder of his brother.
Neurofibromatosis is a painful disease with can result in impaired vision, learning impairment, and even cancer, according to the non-profit research group Mayo Clinic.
It is not contagious but its effect on the appearance of sufferers often leads to social discrimination.