Teaching Case

A 37-year-old female presented with complaints of diffuse swelling over the right proximal forearm. Serum CRP was within normal limits.

There is destruction of the head, neck, and upper part of the body of the right humerus with soft tissue swelling.

MRI shows destruction of the right humeral head and neck with altered marrow signal intensity and soft tissue component. It is hypointense on TIWI and heterogeneously hyperintense on T2WI and shows a thick-walled peripheral enhancing lesion and synovium is seen.

Tuberculosis is one of the oldest diseases that has plagued humankind since prehistoric ages. [3]

Tuberculosis is an endemic disease in South Asian and African countries with a wide range of presentations. Osteoarticular tuberculosis involves either the synovial membrane or the metaphyseal region via direct spread or hematogenous spread from other viscera-like lungs. The lesion is often destructive with pus formation and the lesion may often get calcified. First, there is an erosion of the free surface of cartilage which can progress to involve the adjacent bone with resultant bone destruction. The hip, knee, and ankle are commonly involved joints. [2]

The tubercular osteomyelitis can involve the bone peripherally or centrally.  When peripheral bone involvement occurs, there is early destruction of the cortex with formation of a large juxtacortical inflammatory mass with small communicating juxtacortical abscesses. It may simulate a sarcoma. [5]

The central variant involves the medullary cavity and is less common. It appears aggressive in nature and is difficult to distinguish from other aggressive tumour and infections. Transphyseal spread of disease is more commonly seen in tuberculosis. [5]

The appendicular skeletal tuberculosis spreads hematogenously through the medullary cavity, causing extensive areas of necrosis. The cystic variant is seen more commonly in children. [4] Initially, non-specific areas of osteolysis may be mistaken for malignancy. [4]

Tubercular disease involving the shoulder is rare. The typical presentation is swelling and severely restricted shoulder movements. Three types of clinical presentation are identified.

1. Type I: caries sicca - patients present with marked wasting of the shoulder and painful restriction of all movement.
2. Type II: caries exudate- patients present with swelling of the joint, cold abscess, and a sinus tract.
3. Type III: caries mobile- patients present with characteristic restriction of active movements of the shoulder but passive movements of varying degrees are present. [1]

The disease can involve the head of the humerus, glenoid, spine of the scapula, or coracoid process. On the radiograph, there is osteoporosis with the erosion of articular margins. Since the joint space is small, multiple and large osseous destructions are commonly seen. Early features are joint space widening due to effusion, soft tissue swelling, and marginal erosions- which are seen on the surface lined by synovium and not cartilage. [2].

Late changes involve symmetrical obliteration of joint space, destruction of bone, and fibrous ankylosis. [2]

 On MRI, synovial hypertrophy is commonly seen which is characterized by hypointense areas on T2WI due to hemosiderin deposition, the rim of synovial lesion on precontrast T1WI, and fluid loculations with enhancing synovial rim.

USG-guided aspiration of the collection was performed, and core biopsy showed mixed inflammatory cells with predominant lymphocytes likely suggestive of granulomatous inflammation.

Differential diagnosis of infective arthritis should be kept when there is destruction of the bone. Synovial hypertrophy with fluid collections and sinus formation are important pointers for granulomatous inflammation. Late stages of infection may show calcification which should not be confused with the osteoid matrix as there will be periosteal reaction and less joint involvement in osteoid tumour.

Regarding the drug treatment of skeletal tuberculosis, the WHO recommends treatment in 2 phases: an intensive phase and a continuation phase. Most of the cases of spinal tuberculosis required surgery. Surgery improved these patients' postoperative neurological deficits, pain, and spinal alignment. [3]