When do you consider genetic testing in patients with suspected hereditary brachial plexopathy?

There are two hereditary disorders associated with brachial plexopathy: 1) Hereditary neuralgic amyotrophy (HNA), which is caused by SEPT9 mutations ~70% of cases, and 2) Hereditary neuropathy with liability to pressure palsies (HNPP), which can manifest as a painless brachial plexopathy especially in young people after either sleeping on the same side or loading the shoulder with weight (e.g. backpack). There are some differences between the two.

In HNA, the attacks are very painful at onset, a...