All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
Studying human pathology or any other discipline that falls under the category of beneficial secular science that are needed by the Muslim community is considered a collective religious obligation. This means that a group of Muslims are obliged to learn that discipline in proportion to the needs of the Muslim community. In fact, this is a good enough reason for Muslims to be greatly concerned with such disciplines. Verily, learning these beneficial sciences is part of the required preparation with which Allaah has commanded us. Allaah, The Exalted, says (what means): {And prepare against them whatever you are able of power and of steeds of war by which you may terrify the enemy of Allaah and your enemy and others besides them whom you do not know [but] whom Allaah knows. And whatever you spend in the cause of Allaah will be fully repaid to you, and you will not be wronged.} [Quran 8:60]
Thus, the answer is not simply to say that it is permissible to learn this discipline; rather, it may be a religious obligation, either an individual or collective one. For further information, please refer to Fataawa 84369 and 86424.
However, the Muslim should devote such a good deed (learning beneficial sciences) sincerely and solely to Allaah, The Exalted, and intend to benefit the Muslim community in order to be rewarded for it and brought closer to Allaah in addition to the benefits one gains by them in the worldly life. There is revealed evidence that good intention renders everyday activities, which are not usually rewardable, as acts of worship and rewardable good deeds. The Prophet, sallallaahu ‘alayhi wa sallam, said: "You will be rewarded for whatever you spend for the sake of Allaah even if it were a morsel which you put in your wife's mouth.” [Al-Bukhari and Muslim]
Allaah Knows best.