Want to kvetch about your illness online? PatientsLikeMe, a free data-sharing service, invites you to come over. The Cambridge, Massachusetts-based company announced on April 11 its plan to expand its service to include more than 500 illnesses from the initial 22 chronic illnesses it offered previously.

As more and more people are comfortable sharing the intimate details of their lives online via blogs and social networks, the future of health-related virtual communities is looking brighter than ever - with thousands of people logging on to share side effects, treatment options, test results, and coping strategies. Data-rich virtual communities, such as PatientsLikeMe, HealthCentral, and CureTogether, have been drawing a crowd in the past few years, offering a platform for patients with chronic illnesses such as fibromyalgia, depression, and multiple sclerosis to share information and connect.

PatientsLikeMe cofounders Ben and Jamie Heywood launched their site in 2008 after their brother Stephen was diagnosed with amyotrophic lateral sclerosis (ALS, also known as Lou Gehrig's disease). Earlier this year, the company tested a new design with the 100,000 members of its community, and is now ready to launch the revised product to new members. CureTogether, which rates treatment options for more than 500 illnesses, boosts 26,000 members. HealthCentral, a large-scale health content site offering virtual communities, draws 17 million users to its network of health-related sites per month.

A few other virtual communities for those dealing with serious illness include Upopolis, which helps young patients, especially those in a hospital, stay wired with school friends and family in a format similar to Facebook but packed with "kid-friendly" tools. Also MDJunction offers online support groups to discuss feelings, ask questions, and share hopes about recovering from an illness with like-minded people.

PatientsLikeMe: http://www.patientslikeme.com
HealthCentral: http://www.healthcentral.com
CureTogether: http://www.curetogether.com
MDJunction: http://www.mdjunction.com