Karin's Mother was a member of the Uzumaki Clan who lived in Kusagakure.

After her home village was destroyed, Karin's mother came to Kusagakure while her daughter was still young. The two were allowed to stay, provided that the mother would use her powers to heal the injured of the village.

As a direct descendant of the Uzumaki clan, she had a remarkably powerful life-force, granting her immense vitality, longevity, and healing powers. Even more, she could transmit her healing to anyone who bit her and sucked on her chakra, immediately healing any injury.

(Source: Narutopedia)