Epidemiology and Clinical Characteristics of Musculoskeletal Extrapulmonary Tuberculosis in Lagos, Nigeria

Globally, tuberculosis (TB) remains a major cause of morbidity and mortality from infectious diseases. It poses a substantial public health challenge. According to the World Health Organization global report, TB was the leading cause of death from infectious disease in 2019 and the second leading cause in 2020 (after COVID-19) [1, 2]. Among various forms of TB, musculoskeletal TB is particularly concerning. It accounts for 10%–15% of TB cases in developing nations [3]. This form of extrapulmonary TB (EPTB) often presents atypically, particularly in human immunodeficiency virus (HIV) coinfected patients, where it often manifests in areas outside the lungs, such as lymph nodes, pleura, and osteoarticular systems [4].

Diagnosing EPTB is challenging due to its unconventional presentation. Although histologic diagnosis via tissue biopsy is preferred for its accuracy, it is not always feasible in resource-limited settings. Microbiological cultures, the gold standard for detecting tubercle bacilli, are time-consuming and not universally accessible [5]. As a result, physicians often rely on clinical judgment and radiologic investigations. Previous studies have indicated that factors like gender, race, and comorbidities, particularly HIV status, significantly influence the epidemiology of EPTB [6-8]. In West Africa and Nigeria, male gender and positive HIV status have been strongly associated with EPTB, as shown in studies from Ghana and Benin Republic [9, 10].

In Nigeria, the epidemiological profile of EPTB, especially its musculoskeletal form, is not well documented. This lack of data hinders a comprehensive understanding of its prevalence and clinical manifestations. Therefore, this study analyzed the burden of musculoskeletal EPTB over a 4-year period (2020–2023) at a Federal tertiary hospital in Lagos, Nigeria. It examined demographic factors and clinical presentations, aiming to provide insights that could improve diagnostic methods, treatment strategies, and patient outcomes for EPTB in Nigeria.

This was a retrospective cross-sectional study. We reviewed medical records of 137 patients diagnosed with musculoskeletal EPTB at a Federal tertiary hospital in Lagos, Nigeria, over a 4-year period from January 1, 2020, to December 31, 2023. This facility is a specialized center for managing bone and joint diseases, including trauma, burns, and plastic surgery, and it also offers services in physiotherapy, TB diagnosis, research, and training. The hospital, supported by the Lagos State TB, Buruli Ulcer, and Leprosy Control Program, plays a crucial role in providing comprehensive TB screening, diagnosis, and treatment.

Data extraction took place in May 2021 and was conducted by accessing the Health Facility TB Treatment Register maintained by the National TB Program. The data extraction process was repeated annually to ensure the inclusion of records up to 2023. The primary diagnostic tools employed for confirming EPTB cases included X-ray imaging, GeneXpert testing, and biopsy procedures. Detailed demographic and clinical data were collected for analysis, including variables such as age, gender, HIV status, and the specific site of EPTB. HIV testing was performed using rapid antibody tests, and in cases where initial results were inconclusive, confirmatory testing was conducted using enzyme-linked immunosorbent assay (ELISA). Data was analyzed by using SPSS version 25.0 and the results were presented as frequencies and proportions.

The study adhered to ethical guidelines. Approval was obtained from the hospital ethics review board. Informed consent was waived due to the retrospective nature of the study. Patient confidentiality was maintained throughout the data collection and analysis process. All personally identifiable information was removed before analysis, ensuring that individual patients could not be traced.

A total of 137 musculoskeletal EPTB cases were diagnosed between 2020 and 2023 at the Federal tertiary hospital in Lagos, Nigeria. Over this period, trend in EPTB cases showed variability, with a slight decrease in 2021(31) and 2023(28), but a sudden increasing trend when looking from 2023 in number of cases (Figure 1).

The current study offers valuable insights into the epidemiology of musculoskeletal EPTB in Lagos, Nigeria. Our findings reveal that spinal TB is the predominant form of Musculoskeletal TB, accounting for 94.2% of cases over a 4-year period. This aligns with existing literature from various global regions, including Nigeria, China, and the United States, where spinal TB is often the most affected site [11-13]. The consistency in these findings suggests a possible universal mechanism for TB spread, likely hematogenous or lymphatic, originating from pleural disease. However, our emphasis on spinal TB contrasts with data from Pakistan and India, where lymph nodes are more commonly affected [14, 15]. These differences could be due to regional variations in epidemiology, potentially influenced by genetic, environmental, and healthcare factors, or they might reflect methodological discrepancies in the studies.

Our study utilized a comprehensive diagnostic approach, incorporating X-ray, GeneXpert, and biopsy techniques. This methodology likely contributed to the higher detection rates of spinal TB in our context, similar to the studies conducted in China and Nigeria that employed advanced diagnostic tools [12, 16]. In contrast, studies from regions like Pakistan and India, which relied more on clinical symptoms for TB diagnosis, reported different patterns in EPTB site prevalence, with a significant emphasis on lymphatic involvement [14, 15]. This highlights the importance of region-specific diagnostic strategies in accurately identifying and managing EPTB.

Regarding treatment outcomes, our study found that 64% of patients successfully completed their treatment, while 9% were LTFU, and 5% died during the treatment period. These results are consistent with findings from other studies, which also reported suboptimal treatment success rates among EPTB patients. For instance, a study conducted in Bahawalpur, Pakistan, reported a 71.1% treatment success rate among EPTB patients, with a significant proportion of patients (25.4%) lost to follow-up, which is higher than our findings [17]. The higher LTFU rate in the Pakistani study underscores the challenges in maintaining patient adherence to TB treatment, particularly in regions with similar healthcare infrastructure.

Similarly, a study in Malaysia reported a treatment success rate of 67.6% among EPTB patients, with a high rate of unsuccessful outcomes associated with co-morbidities such as HIV and diabetes mellitus [18]. In our study, 94.2% of the patients were HIV-negative, which may have contributed to the relatively higher treatment success rate compared to the Malaysian study. However, our study still highlights the need for integrated EPTB and HIV screening, as the presence of HIV co-infection is a known risk factor for poor treatment outcomes.

Moreover, a study from Northwest Ethiopia reported a treatment success rate of 88.4%, which is significantly higher than the success rate observed in our study [19]. The Ethiopian study identified factors such as male gender, normal nutritional status, and HIV-negative status as being associated with successful treatment outcomes. These factors were similarly relevant in our study, where the majority of patients were male and HIV-negative. However, the discrepancy in treatment success rates between our study and the Ethiopian study may reflect differences in healthcare delivery, patient management, and adherence to treatment protocols across the regions.

Victor Abiola Adepoju: conceptualization, methodology, investigation, formal analysis, writing – original draft. Safayet Jamil: formal analysis, writing – review and editing, conceptualization, investigation. Ify Genevieve Ifeanyi-Ukaegbu: formal analysis, data curation, investigation, writing – review and editing. Olusola Daniel Sokoya: formal analysis, data curation, investigation. ABM Alauddin Chowdhury: writing – review and editing, data curation, formal analysis. Mohammad Shahangir Biswas: conceptualization, methodology, data curation, supervision, writing – original draft, writing – review and editing.

The authors have nothing to report.

The authors declare no conflicts of interest.

The lead author Mohammad Shahangir Biswas affirms that this manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.