Consider a hypothetical scenario: Rosa, a 35-year-old healthy woman, visits a primary care physician at a community clinic for a routine checkup. She immigrated to the United States one year ago from Mexico, a country with a higher prevalence of tuberculosis (27 cases per 100,000 people) [1] than the US [2]. The primary care physician recommends screening for latent tuberculosis infection (LTBI) based on established guidelines. Rosa's purified protein derivative (PPD) skin test is positive, and she is started on isoniazid (isonicotinylhydrazide or INH). While taking it, she develops jaundice and lower extremity edema and is admitted to the hospital. She becomes critically ill and is found to have fulminant hepatic failure-acute liver failure-an iatrogenic consequence of INH treatment. A liver transplant would save her life, but Rosa is deemed not to be a good candidate for transplant because she is poor, uninsured, and undocumented. She dies of liver failure and sepsis. Here we consider the unique risks that undocumented immigrants incur when accepting LTBI therapy and the physician's duty to disclose these risks, and we present policy and clinical solutions that would protect public health without placing undue burden on undocumented immigrants. LTBI screening and treatment serve a dual purpose of preventing reactivation of tuberculosis (reactivation TB) in the individual and protecting public health by preventing the spread of TB in the community. Although 9,421 new TB cases were reported in the US in 2014, an estimated 11 million people in the US are living with LTBI [2,3]. The lifetime risk of reactivation TB in those with LTBI is 10 percent, but identification and treatment of LTBI can reduce the risk of active disease by 60-90 percent [4][5][6].LTBI screening and treatment are particularly important for immigrants from regions where TB is common. Over half (66 percent) of US LTBI cases occur in people born outside the US, and the case rate of reactivation TB among that group is about 13 times higher than among persons born in the US [2]. The Centers for Disease Control and Prevention (CDC) recommend LTBI screening for all immigrants from high-prevalence countries who have lived in the US for less than five years [7]. There were approximately 7 million new immigrants in the US in 2010, including approximately 2.7 million from three high-prevalence countries: Mexico, China, and India [8]. This population also includes 1.8-2.3 million undocumented immigrants [9,10]; these are immigrants who