Morgellons Disease
This is an unusual disease, and while there are some unusual thoughts about where it comes from, the Bacterial hypothesis seems to be the most logical and promising.
As discussed and referenced on Wikipedia.org:

Three members of the Morgellons Research Foundation, including Raphael Stricker, Director and former President of the International Lyme and Associated Diseases Society (ILADS), and Ginger Savely, also an ILADS member, authored an article about Morgellons published by the American Journal of Clinical Dermatology in early 2006. The authors wrote that "Morgellons disease may be linked to an undefined infectious process," and reported that many patients with Morgellons disease have positive Western blots for Borrelia burgdorferi, the causative agent of Lyme disease, and treatment with anti-bacterials appropriate for Lyme disease leads to remission of Morgellons symptoms in most patients. Dr. Harvey, another member of ILADS, has also stated there is serological evidence of bacterial pathogens in Morgellons patients, but did not provide any such evidence.

Stricker, along with Citovsky, MRF board member from the State University of New York at Stony Brook and a researcher on plant pathogens, reported in January, 2007, that Morgellons skin fibers appear to contain cellulose, and PCR screening of samples from two Morgellons patients produced evidence of DNA from Agrobacterium, a plant-infecting organism known to induce cellulose fibers at infected sites within plant tissues. They stated that if confirmed, Agrobacterium could be the first instance of plant infecting bacteria involvement in human disease. However, Agrobacterium is already known to be responsible for opportunistic infections in humans with weakened immune systems, but has not been shown to be a primary pathogen in otherwise healthy individuals.