A 35-year-old male patient, originally from India, presented with worsening pain of the left wrist over the course of two months. He was otherwise asymptomatic with no history of trauma. Following failed conservative treatment in primary care, a plain radiograph of the wrist was performed.
A well-defined lytic lesion in the distal ulna can be seen with no cortical break identified on plain film. An MRI scan was then performed. On the T2 image a soft tissue mass within the distal ulna, erupting through the cortex of the bone and extending into the adjacent adipose tissue on the palmar aspect of the wrist joint was seen. The lesion enhanced vividly on administration of intravenous gadolinium. The lesion was in contact with the flexor carpi ulnaris tendon but invasion was not seen. The triangular fibrocartilage complex was intact and there was no involvement of the radius or carpal bones. No surrounding synchronous lesions were identified. In terms of classification, as the anterior margin of the lesion is indistinct but there are no permeative or moth-eaten features, the Lodwick classification would be grade 1C. This gives a likelihood of malignancy of 36%.
Background: The differential diagnosis for a lytic bone lesion is wide-ranging and includes infectious, neoplastic and cystic aetiologies. Factors such as age, previous medical history, family history, exposures, and the characteristics of the lesion itself in terms of location and radiographic appearance can be used to narrow the differential. The Lodwick classification system (illustrated in figure 3) can be used to evaluate the appearance of a lytic bone lesion and assess the likelihood of malignancy based on appearance, and has been demonstrated to be accurate and reliable [1, 2].
Clinical Perspective: The MRI findings in our case were determined to be most consistent with neoplasia and due to uncertainty regarding the histological origin of the lesion; an image-guided biopsy was performed. This in fact demonstrated necrotising granulomatous inflammation with well-formed granulomas and some central necrosis, consistent with a diagnosis of a tuberculoma. On further questioning our patient had been exposed to tuberculosis (TB) as a child but had never developed any manifestations of infection. A tuberculoma is a well-defined area of granulomatous inflammation caused by localised infection with mycobacterium tuberculosis and represents an extra-pulmonary manifestation of TB. Musculoskeletal involvement by TB is rare in comparison to other forms of the disease, with extra spinal musculoskeletal TB specifically occurring in only 1-2% of cases [3]. It most commonly involves the spine but can also involve large weight-bearing joints, long bones, the skull and soft tissues.
Imaging Perspective: Due to its imaging appearance it can often mimic other pathologies such as malignancy on imaging, and is therefore an important differential diagnosis to the considered in anyone with a potential exposure to TB. The typical appearance on plain films is that of a lytic and well-defined lesion with or without surrounding sclerosis. Magnetic resonance imaging (MRI) is the modality of choice for diagnosis and may also detect any associated soft tissue or bone marrow abnormalities. MRI may also demonstrate intraosseous involvement earlier than with other imaging modalities. Marrow changes are demonstrated as areas of low and high signal intensity on T1- and T2-weighted images respectively, and show enhancement after the intravenous administration of gadolinium. Areas of necrosis appear hyper-intense on T2- weighted images and show no enhancement [4].
Outcome: In most cases of musculoskeletal TB, treatment with multi-drug chemotherapy regimens used for other forms of TB is sufficient. In severe cases, however, surgical intervention can be required.
Tuberculoma of distal ulna
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From the provided plain X-ray of the left wrist, a relatively well-defined lytic lesion can be observed in the local area. The lesion has a relatively clear margin, with some degree of sclerosis or marginal reaction around it, presenting an overall focal change.
MRI shows an abnormal signal in the distal radius of the left wrist or the proximal carpal bones. On T1-weighted images, the lesion appears hypointense; on T2-weighted images, it appears hyperintense, with a relatively well-defined boundary. After contrast enhancement, some peripheral areas of the lesion show enhancement, while the central region appears necrotic or cystic (high signal on T2, no enhancement), suggesting possible granulomatous or necrotic changes within the lesion. In MRI, there is also a connection with adjacent soft tissues; although overt soft tissue swelling or inflammatory infiltration is not significant, potential soft tissue involvement related to the lesion cannot be ruled out.
Based on the patient’s age (35 years), history of tuberculosis exposure, imaging findings (lytic lesion with necrotic areas), MRI evidence of granulomatous inflammation, and histopathological biopsy results, the most likely diagnosis is: Tuberculous Osteomyelitis (Bone Tuberculosis, also referred to as a “tuberculoma”).
Pathological findings indicate necrotizing granulomas consistent with Mycobacterium tuberculosis infection, further supporting this diagnosis.
If any doubts remain or to assess possible drug-resistant strains, further blood tests, cultures, and molecular biological tests (such as nucleic acid amplification) are recommended.
Throughout these exercises, attention should be paid to pain, swelling, or other discomfort. If severe pain, restricted range of motion, or other adverse reactions occur, seek medical advice for re-evaluation or adjustment of the rehabilitation plan.
This analysis report is based on the available imaging and clinical information for reference in clinical decision-making and does not replace an in-person diagnosis or professional opinion from a qualified physician. If you have any concerns or if your condition changes, please consult a specialist or medical institution for further evaluation and treatment.
Tuberculoma of distal ulna
