At her Superbug blog, Maryn McKenna reports on a disturbing, but not unexpected development: over the past three months, 12 cases of tuberculosis at a single Mumbai hospital have been found to be resistant to all the drugs used to treat the disease.

This is not the first time totally drug-resistant tuberculosis (TDR-TB) has been reported; in 2009, McKenna notes, the disease was identified in 15 patients in Iran. This was only three years after extremely drug-resistant tuberculosis (XDR-TB) was first identified. The drivers of such rapidly evolving drug resistance include inadequate diagnostics and insufficient treatment. Too few facilities have the capacity to diagnose resistant cases of tuberculosis, so patients with resistant cases of TB may never be prescribed the drugs to which their infections are susceptible. Even those who get an appropriate diagnosis and prescription may not be able to afford the drugs, or might stop the long and grueling course of treatment too soon.

According to the Times of India, the average age of the 12 patients is just 32, and all have suffered from tuberculosis for at least two years. Tuberculosis caused 15% of Mumbai’s 2010 deaths, and the lack of sufficient diagnostic capability means that the city may have far more than 12 cases of a disease for which there is no effective drug therapy.

For more of the sobering details on these cases and drug-resistant TB, head over to Superbug. To get a sense of the immense challenges of treating tuberculosis in India, read Michael Specter’s 2010 New Yorker piece “A Deadly Misdiagnosis.”