Lawsuits stemming from employees who have missed work due to the need to care for a loved one are on the rise, according to a new report.

The lawsuits, which usually involve workers who have needed to care for an elderly parent or spouse or a child with a disability, have increased nearly 400% in the last 10 years, according to data from the Center for WorkLife Law at the University of California.

Many of the cases allege that an employer denied leave or retaliated against a worker. Employers also violated the federal Americans with Disabilities Act by denying workers accommodations to care for a relative with a disability, according to the suits. In response to the rise in the number of such lawsuits, the U.S. Equal Employment Opportunity Commission recently has issued its first guidance for employers about the issue.