Suggest Treatment For Symptoms Of Raynaud's Disease
Not a bug issue, a rheumatological cause may be considered.
Detailed Answer:
I read your question carefully and I appreciate your concern about your friend.
Regarding his thoughts of bugs consuming him I must say that there is no basis for that. There are no such parasites which crawl under the skin, it is not possible.
That being said he the color changes of the fingertips you describe seems like what is called Raynaud's phenomenon, caused by vasospasms of blood vessels. It may be without a cause or may be in the setting of rheumatological conditions such as rheumatoid arthritis, lupus etc. The fact that he has had joint issues as suggested by the surgeries of the neck and hips does indicate towards such a rheumatological condition. The swollen hands and feet may be in such conditions as well. So it should be investigated in that direction. Such conditions are commonly associated with peripheral neuropathy which may cause abnormal skin sensations leading him to those false beliefs of bugs under the skin (for which a psychiatric consult is necessary anyway).
I remain at your disposal for other question.