Patients with HIV are susceptible to mycobacterium infection. In the case of fast-growing mycobacteria, the group to which Mycobacterium fortuitum (M. fortuitum) belongs, infections have been described in the skin, lungs, lymph nodes and disseminated disease. We present the case of a 43-year-old male patient with pre-diagnosis of HIV in antiretroviral therapy, which comes as a fever, asthenia, weight loss and chronic diarrhea. Abdominal tomography is performed and hepatosplenomegaly is evidenced with nodular lesions in the spleen. The splenic culture was finally positive for M. Fortuitum, with positive PCR to Mycobacterium tuberculosis. The current treatment protocols for this type of infection are based on the susceptibility shown in the cultures performed. With regard to coinfections between M. Fortuitum and Mycobacterium tuberculosis, in HIV positive patients, there are even less information.