MU-2
Flight Crew Commercial; Flight Crew Multiengine
Flight Crew Last 90 Days 30; Flight Crew Total 2100; Flight Crew Type 400
Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Returned To Clearance; Flight Crew Took Evasive Action
Human Factors; Weather
I was at FL240 enroute from ZZZ to ZZZ1 when the aircraft started picking up ice. There had been PIREP reports of ice between 14;000 to 18;000 and 22;000 to 24;000.  I requested to descend and was given 22;000 by ATC. I was still picking up significant ice at 22;000 and requested lower altitude. The ice was continuous and becoming moderate at 20;000 and the aircraft was accumulating a significant amount of ice. I had to keep descending and while trying to control the aircraft; I got into a left turn bank thereby deviating from the assigned heading. The ice piled on extremely quickly and it wasn't until I got around 15;000 that I finally got out of the ice and got back on course heading westbound. Although I was in significant ice; I believe my attention became too focused on the ice accumulation thereby distracting me from maintaining the heading and also assigned altitude.
MU-2 GA pilot reported a heading deviation after being distracted while dealing with ice accumulation.