Diagnosis of tuberculosis in children is challenging because of variable clinical symptoms and no specific signs. We report a case of tuberculous osteomyelitis of the ribs, which demonstrates difficulties associated with the diagnosis of generalized tuberculosis in an 8-year-old child (correct diagnosis was established after 1.3 years). Diagnostic procedures included: Mantoux test, skin test with recombinant tuberculosis allergen, computed tomography, pathomorphological and bacterioscopic testing. The patient presented with disease progression and lesions to the lung tissue, pleura, and ribs and did not respond to antibacterial therapy, hormones, and cytostatics. This required repeated diagnosis revision. The diagnosis of tuberculosis of the right 4th and 5th ribs was confirmed after surgery using bacterioscopic and immunohistochemical examinations. The child received comprehensive treatment in a specialized tuberculosis hospital and had positive dynamics. Despite the correct routing, low suspicion for tuberculosis in primary and secondary healthcare institutions has led to an insufficient use of currently available diagnostic methods and late diagnosis of tuberculosis in a child residing in a megapolis. Key words: generalized tuberculosis, children, tuberculosis of the rib, immunodiagnostics, diagnosis of tuberculosis, immunohistochemistry