A youg Asian female presented with painless neck mass. Few months later, she represented with Knee and foot pain. The diagnosis was established only after an excision biopsy of cervical lymph node.
A youg Asian female presented with painless neck mass. Fine needle aspiration drew pus, which was negative on staining and culture. She was treated with antibiotic with symptomatic improvement. Four months later she represented with pain and tenderness over the tibial tuberosity and foot.
X-ray of the knee showed well-defined lucent lesion in the tibial tuberosity (fig.1). Whole body isotope bone scan showed three foci of increased tracer activity in the tibial tuberosity, calcaneum and mid foot (fig.2). MRI of the knee showed thick-wall cavitating lesion with sclerotic rim and non-enhancing cavity (fig.3). Chest x-ray showed clear lungs.
The diagnosis of tuberculosis was suggested. Lymph nodes excision biopsy from the neck showed necrotizing granuloma and the culture grew acid-fast bacilli of tuberculosis. Anti-tuberculosis chemotherapy was started and a follow-up radiograph of the knee showed healing of the tibial tuberosity lesion (fig.4).
Skeletal involvement constitutes less than 3% of the extra pulmonary presentations of tuberculosis. The incidence of disseminated skeletal tuberculosis reported ranges from 5% to 10% (1). Osteoarticular tuberculosis shows a predilection for joints and paraarticular areas. Tubercular osteomyelitis comprises approximately 2% to 3%of all cases of osteoarticular tuberculosis. The feet are involved in only 8% to 10% of the patients with osteoarticular tuberculosis (2). Disseminated skeletal tuberculosis may result from haematogenous dissemination of a primary tuberculous lesion or from repeat impregnations on different occasions.
Symptoms may precede discernible radiological changes by 4-8 weeks and there is a wide spectrum of imaging appearances. The common presenting features of tubercular osteomyelitis are pain and swelling with abscess and sinus formation. Radiographs reveal irregular cavities and areas of bone destruction with little surrounding sclerosis or periosteal reaction, unless secondary infection through a sinus supervenes. If complicated by secondary infection, it may be difficult to differentiate tubercular osteomyelitis from pyogenic osteomyelitis.
Magnetic resonance imaging can show abnormal signals even in the predestructive stage, as early as 6 to 12 weeks of the onset of infection. MRI usually reveals a nonspecific marrow edema, seen as an abnormally high signal on T2-weighted images and a black signal on T1-weighted images. Nevertheless, MRI can show some cortical breaks, early cavitations, and soft tissue collections. During the destructive phase of the disease, CT clearly shows the sequestration and cortical breaks. CT also outlines the extent of the bone destruction and is helpful in facilitating biopsy (3).
The rarity of the problem and the ability of tuberculosis to mimic other diseases combined with a lack of awareness of the treating physician, often leads to diagnostic delays. Skeletal tuberculosis should be included in the differential diagnosis of chronic/subacute monoarticular arthritis, chronic osteomyelitis and chronic abscess or draining sinus. Multifocal tuberculosis can also be mistaken for metastasis.
The basic treatment of patients with skeletal tuberculosis is adequate and prolonged antituberculous therapy. Plain radiographs, CT scans, and MRI done during the follow-up of these patients may show advancing lesions up to 3 to 4 months after the start of treatment. This is because the imaging appearances lag behind the biologic process of repair. Even after complete clinical and radiological healing, there may be residual cavities observed on serial CT scans or on radiographs. These are of little consequence regarding the durability of healing and chances of recrudescence. These cavities are filled with fibrous or fibro-osseous tissue and do not warrant surgical intervention. If however, the imaging done at 6 to 7 months of adequate chemotherapy shows evidence of deterioration of the lesion, one should suspect a non-responding lesion, which may be caused by drug resistant disease, an immunocompromised state, or a non-tuberculous disorder. Repeat biopsy and tissue diagnosis (with or without debridement) becomes mandatory in these patients (2).
Mutifocal Skeletal Tuberculosis
Based on the provided X-ray, bone scan, and MRI images, the following observations are noted:
1. Localized bone destruction around the knee joint (especially the proximal tibia), displaying irregular contours with low-density or cavity-like changes. There is no obvious surrounding sclerosis.
2. On MRI, the lesion area predominantly shows low signal on T1 and high signal on T2, with signs of bone marrow edema and varying degrees of cortical bone destruction. Abnormal signals can be observed in some soft tissues.
3. The bone scan reveals abnormal localized uptake, possibly reflecting inflammation or infection.
4. Considering potential changes in other areas of the foot or lower extremities, there is an indication of multifocal bony lesions or soft tissue involvement in this case.
In summary, skeletal tuberculosis (or tuberculous osteomyelitis) is highly suspicious in this case.
Taking into account the patient’s age, clinical presentation (initial painless swelling of cervical lymph nodes followed by knee and foot pain), the pathological confirmation of cervical lymph node tuberculosis, and the imaging findings indicative of chronic low-grade destructive bone lesions, the most likely final diagnosis is:
Multifocal bone and joint tuberculosis (tuberculous osteomyelitis).
If any doubts remain or if follow-up imaging after treatment does not match the expected progress, a repeat biopsy of the lesion may be required to rule out drug-resistant tuberculosis or other non-tuberculous infections.
Disclaimer: This report provides a reference analysis based on the current clinical and imaging data. It cannot replace a professional physician’s in-person diagnosis and treatment advice. Patients should undergo evaluation and treatment under the guidance of a specialist. If you have any concerns, please seek prompt medical consultation.
Mutifocal Skeletal Tuberculosis
