Partners HealthCare said last week it lost $22 million from operations in its most recent fiscal year.

The Boston-based health system could have managed a surplus if it weren’t for its struggling health insurance arm. Neighborhood Health Plan, which Partners bought in 2012, lost $202 million in the year ended Sept. 30. Executives said the steep losses resulted from higher-than-expected medical claims, high costs related to hepatitis C drug Sovaldi and troubles with the Massachusetts insurance exchange. The health plan has more than 330,000 members.