The majority of extra-pulmonary TB cases involve the pleura, musculoskeletal and lymphatic systems. Most cases verified to have a previous pulmonary TB origin . TB bacilli spread over the pleural cavity, starting from a pulmonary infection focus on that occasion, immigrates through the blood vessels or lymphatics to other organs developing extrapulmonary TB.
The distribution of age and site of musculoskeletal TB has been previously studied. Overall, of all TB cases, 1-4 % showed musculoskeletal involvement. In a retrospective and observational study conducted in a tertiary area with the highest prevalence of TB worldwide, three peaks in the first, third, and sixth decade of life were found . However, some reports highlighted a bimodal age distribution . In a nine-year single-center experience, the rate of musculoskeletal TB was found as 4 % . In our study, the rate of musculoskeletal system TB was 3.2 %, which was compatible with the previous reports. On the other hand, the mean age was 44 years, and 90 % of all cases were adult patients. We did not find an age peak in childhood or in the advanced age group. Musculoskeletal TB is distributed almost equally among males and females in our sample group.
In the literature, most of the TB cases present with spine involvement. More than 10 % of patients with extra-pulmonary TB have skeletal involvement . The most common form of skeletal TB is the Pott’s disease, comprising approximately half of musculoskeletal TB cases, and followed by TB arthritis and extra-spinal TB osteomyelitis . In the retrospective study done by Held et al. , 78 % of the cases had spine TB while the remaining 21.6 % had extra-spinal diseases, comprising hip, knee, foot/ankle, shoulder, elbow, wrist, and others. The thoracic region of the vertebral column is commonly involved . Likewise, in our study, the prevalent anatomically affected location was the spine (23 of 31 patients; 75 %) as well as hands, knee joint, costa, shoulder, patella, and psoas muscle. Only two cases in this study were involved with psoas muscle. These two cases had both concomitant pulmonary TB. The psoas muscle is a retroperitoneal muscle that originates from the lateral borders of T12 to L5 vertebrae and ends as a tendon that inserts into the lesser trochanter. The primary TB of iliopsoas compartment abscess with occult cause rarely encountered in the clinical practice and is generally idiopathic.
The joints’ TB infection comes after hematogenous spread or direct invasion from neighboring tissue of TB osteomyelitis. Mostly monoarticular joints are involved such as the knee and hip. Oligoarticular/polyarticular patterns are very rare, ranging from 5 to 15 % of cases, sometimes with small joint involvement, and ordinary in immunosuppressed patients . A patient in our series (male, 38-year-old, butcher), TB was detected in the biopsy performed a long time after the local infectious swelling developed with a knife sticking in the left hand at the workplace.
The delays in the diagnosis of musculoskeletal TB have been sufficiently presented . This may be due to the patients’ uncertain histories, perhaps complicated by inaccurate stories of irrelevant trauma, and lack of presence of a concomitant pulmonary involvement. In the current study, complaints of 70.9 % of cases have been started as back pain. Therefore, these patients have been investigated in neurosurgery, orthopedic and traumatology, or algology clinics for a long time. The patients usually presented with nonspecific symptoms such as back pain, mass on back/neck, knee pain, wrist swelling, chest pain, shoulder pain, hand pain, or abdominal pain.
There were some limitations to our work. Primarily, because of the retrospective nature of our study, it was not possible to obtain detailed information of every patient. Furthermore, because the patient registry systems of dispensaries and hospitals are not integrated, monitoring and clinical information, such as misdiagnosis or delayed diagnosis for other reasons, that are not recorded in the ledger could not be accessed. In Turkey, all patients suspected with TB, whether they are pediatrics or adults, are directed to dispensaries to confirm their diagnosis and to give their treatment. However, dispensaries do not have a chance to diagnose possible overlooked cases unless clinicians from other branches express suspicion of TB. Even if all musculoskeletal TB patients living in this area have to apply to this dispensary as it is the only TB center in the city, the present results should not be generalized to the entire Turkey.