Bob Herman May 17
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DOJ pursues UnitedHealth in second Medicare fraud suit
Jim Mone / AP

The Department of Justice is intervening in a second whistleblower lawsuit that alleges UnitedHealth Group, the largest health insurance and services company in the country, has defrauded the Medicare Advantage insurance program by exaggerating people's medical diagnoses to obtain more federal dollars.

Why this matters: These lawsuits have some explosive allegations and threaten a company that dominates a growing and lucrative Medicare industry. In addition, the Center for Public Integrity and a federal watchdog agency have reported numerous instances of insurers manipulating a Medicare patient's "risk score" to get more money.

The bottom line: This will be one of the most closely watched federal court cases in health care considering billions of taxpayer dollars are on the line.