Bone TB Uncovered: The Silent Pulmonary Connection and Its Transmission Risk

Abstract

Tuberculosis (TB) remains a major global infectious disease burden, with Extrapulmonary TB (EPTB), particularly musculoskeletal TB, contributing significantly to morbidity and disability. Traditionally, bone TB has been regarded as a non-contagious biological \"dead end,\" isolated from active pulmonary disease. However, this paper reviews accumulating evidence from modern radiology (High-Resolution Computed Tomography or HRCT) and whole-genome sequencing (WGS) that challenges this classification. Genomic studies consistently place musculoskeletal isolates within active pulmonary transmission clusters, and HRCT frequently reveals occult or subclinical pulmonary lesions in bone TB patients that standard chest X-rays miss. These hidden lung foci represent the true pulmonary reservoir that disseminates bacilli hematogenously to the bone, establishing a unified pulmonary-skeletal transmission axis. We conclude that bone TB is best understood as a downstream manifestation of occult pulmonary infection, and therefore, clinical protocols must be updated to mandate HRCT and molecular characterization for accurate case classification and effective transmission control.

Introduction

Bone and Musculoskeletal Tuberculosis (TB) remains a significant global health concern, accounting for 1–3% of all TB cases and 10–15% of extrapulmonary TB (EPTB). Musculoskeletal TB, particularly spinal involvement, is often severe and disabling. Historically considered minimally contagious and independent of pulmonary TB, recent epidemiological, radiological, and genomic evidence indicates that many bone TB cases originate from subclinical or occult pulmonary infection, serving as a hidden reservoir for hematogenous spread.

Epidemiology shows peak susceptibility in early childhood, young adults, and the elderly, with HIV coinfection increasing risk and complications. Peripheral joints, spine, and long bones are commonly affected. Drug-resistant TB remains a concern, though less frequent in skeletal disease.

Transmission dynamics challenge the “non-infectious” view of EPTB. Genomic studies reveal shared circulating strains among bone TB patients, while HRCT imaging uncovers subclinical pulmonary lesions missed by standard X-rays, providing pathways for bacillary dissemination to bone. Radiological findings, including micronodules, early consolidation, and necrotizing lesions, explain hematogenous seeding to skeletal sites.

Clinical and diagnostic implications emphasize the need for comprehensive pulmonary evaluation in suspected bone TB cases, improved imaging techniques, and heightened awareness of atypical presentations that mimic malignancy. Understanding these hidden transmission pathways is crucial for accurate diagnosis, effective treatment, and TB control strategies.

Conclusion

The evidence we’ve gathered—from looking at the disease itself, scanning patients, and even mapping the bacteria\'s DNA—tells a clear story: bone tuberculosis is not a separate problem happening in isolation. It’s deeply and strongly connected to an often-hidden infection in the lungs. For years, we’ve relied on old ideas and screening tools like the standard chest X-ray, which frequently misses the subtle, early lung disease. This lack of visibility is why we wrongly classified bone TB as \"non-contagious\" for so long. New tools like High-Resolution CT (HRCT) and whole-genome sequencing (WGS) have pulled back the curtain. They show us two consistent, crucial facts: first, the TB bacteria found in the bone are genetic siblings to the strains circulating in the community’s lungs; and second, most patients with bone involvement have small, previously unrecognized lung lesions. This has profound implications for how we tackle TB: 1) The Real Threat: The genuine source of TB transmission, even for bone patients, is that hidden lung disease. We can\'t afford to ignore it, even if a patient isn\'t coughing. 2) The Policy Shift: Continuing to overlook this subtle lung involvement means we\'re misjudging how infectious these cases really are, leading us to underestimate the community\'s risk. 3) The New Standard: Clinical practice must change. We can no longer evaluate musculoskeletal TB as a solitary issue. We need to mandate HRCT screening and use molecular testing whenever possible. Ultimately, we should stop viewing bone TB as a strange outlier. It is simply a painful, downstream consequence of an infection that starts in the lungs. Recognizing this connection is essential if we want to diagnose patients accurately, protect communities, and finally curb transmission.

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Copyright

Copyright © 2025 Dhananajay Masurkar, Shravni Jagtap , Shravanee Pawar, Omswaroop Bhor Patil, Samruddhi Deshmane. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.