I know ghusl bath is must before Jumma prayer (Friday prayer). Is it possible to pray Jumma prayer without ghusl if someone is sick?
In case the person in question already had Ghusl, even if he/she cannot renew his Ghusl on Friday, he/she may accomplish the Salah. But if he doesn't have Ghusl and he cannot perform it due to his sickness, then he/she will have to perform Tayamum.
"O you who believe! When you intend to offer As-Salat (the prayer), wash your faces and your hands (forearms) up to the elbows, rub (by passing wet hands over) your heads, and (wash) your feet up to ankles. If you are in a state of Janaba (i.e. after a sexual discharge), purify yourselves (bathe your whole body). But if you are ill or on a journey, or any of you comes after answering the call of nature, or you have been in contact with women (i.e. sexual intercourse), and you find no water, then perform tayammum with clean earth and rub therewith your faces and hands. Allah does not want to place you in difficulty, but He wants to purify you, and to complete His Favour to you that you may be thankful." — Qur'an, Sura 5 (Al-Mai'da), ayat 6