Do people who have one autoimmune disease

Yes, there is statistically significant comorbidity with autoimmune diseases.

For both the password and the key pair, I am creating a salt derived from OpenSSL's random number generator. For the password, I am using bcrypt to encrypt with the aforementioned salt. For the key pair, it's a little more complicated. I am using OpenSSL with aes-128-ctr to encrypt the pair, and the key for aes is derived from the password and the salt. Specifically, here's the code I am using in Ruby:

The study Recent Insights in the Epidemiology of Autoimmune Diseases: Improved Prevalence Estimates and Understanding of Clustering of Diseases analysed other studies on the subject. It puts the comorbidity of 29 autoimmune diseases - including, for example, Crohn's, diabetes, rheumatoid arthritis - at around 7 to 9 percent.

Earlier studies put the comorbidity number lower, at around 4 to 6 percent, this appears to depend mainly on what diseases are considered and the quality of the records being reviewed for the large population-based studies. They found that certain diseases "cluster" in patients, for example type 1 diabetes, rheumatoid arthritis and thyroiditis. The reverse is true as well, several of the analysed studies report that rheumatoid arthritis in combination with multiple sclerosis occur together less frequently than expected. More at Videos

Two other main meta analyses on the subject are

Are Individuals With an Autoimmune Disease at Higher Risk of a Second Autoimmune Disorder? in the American Journal of Epidemiology Autoimmune diseases co-occurring within individuals and within families: a systematic review in the journal Epidemiology The conclusion that a significant comorbidity exists and that it's more prevalent between certain diseases is drawn by all these studies the studies, which is also discussed in the first paper I linked.