Could shooting heroin in the arm cause arm lymphedema?

Yes: Injecting any drugs into arm veins can cause scarring of the veins, which increase your risk of swelling. This is not true lymphedema, which is caused by damage to lymph vessels, but the symptoms of swelling can be the same.

Potentially: Lymphedema can result from any type of disruption of lymphatic channels: surgery, trauma, and infection are common causes. If the heroin was injected into tissues rather than into the vein, it can incite an inflammatory reaction which alters lymphatic flow.