What is the ruling on abandoning fasting in Ramadan due to fear of a relapse in vitiligo treatment and a worsening of the disease?

It is out of God's mercy towards His servants that He has not placed any hardship upon them in religion. Thus, He has permitted the sick person who is harmed by fasting to break their fast and make up for that day, based on His (the Almighty's) saying: "And whoever is ill or on a journey - then an equal number of other days." The illness that permits breaking the fast is one with which fasting becomes difficult, or if there is a fear of its worsening, or a delay in recovery due to it. This is what the jurists have stipulated as the illness that permits tayammum (dry ablution). Therefore, if the illness causes a severe disfigurement in the visible limbs and there is a fear of its increase by fasting, then it is among the illnesses that permit breaking the fast.