skeletal sarcoidosis

Skeletal sarcoidosis is an uncommon manifestation of sarcoidosis.

Epidemiology

Skeletal involvement is thought to occur in ~1-13% of patients with sarcoidosis .

Osseous involvement may be more common in black patients .

Clinical presentation

Patients with large bone lesions and vertebral lesions may become symptomatic. The exact symptoms may vary depending on site. It may be accompanied by lupus pernio (chronic, predominantly facial skin lesion resembling frostbite ) or other types of infiltrative skin lesions .

Pathology

Primary skeletal involvement without other organ involvement is extremely rare . Approximately 80-90% patients have concurrent pulmonary involvement .

Location

The phalanges in the hands and feet are most frequently affected. There is typically multiple joint involvement.

Radiographic features

Plain radiograph

Small bone lesions

Radiographic features may include cyst-like radiolucent areas, a lacelike honeycomb appearance (this is typically seen in the hands), or extensive bone erosion with pathologic fractures. The articular spaces are usually intact unless extensive neuropathic lesions develop. A subcutaneous soft-tissue mass or tenosynovitis may also be present.

When there is involvement of other skeletal structures, diagnosis becomes difficult as the condition can mimic various other pathology

Large bone lesions and axial skeletal lesions

Large bone lesions may manifest radiographically as either focal lytic or sclerotic areas. They may even be occult.

In the vertebrae, sarcoidosis can cause osteolytic lesions and disc spaces are usually preserved. Widespread vertebral sclerosis can also occur.

They have been secondary alignment abnormalities deformities due to pathologic fractures with bone collapse.

MRI

MRI may demonstrate fine perpendicular lines extending from the ghost of the cortex and resembling periostitis .

Intermediate-density–weighted MR imaging sarcoidal nodules are typically hyperintense .

MR imaging of large bony lesions usually reveals indistinct or well-marginated lesions of varying sizes.

Reported signal characteristics include:

• T1: large bone lesions are typical low signal 
• inversion recovery: can have high signal
• T2 / PD FS: most cases are high signal
• C+ (Gd): lesions may enhance

Nuclear medicine

Scintigraphic findings become usually positive even before the lesions become manifest at radiography. Both Tcm methylene diphosphonate and Ga citrate imaging may show uptake.

PET/CT

FDG-PET/CT has shown promising results in the detection of extra-thoracic involvement including skeletal lesions .

Differential diagnosis

While classical hand lesions have characteristic features, there is a wide differential for skeletal involvement in other sites

For vertebral lesions, consider

• vertebral metastases 
• multiple myeloma

For calvarial lesions also additionally consider

• eosinophilic granuloma

See also

• musculoskeletal manifestations of sarcoidosis

Siehe auch:

• Sarkoidose
• vertebrale Metastasen
• Multiples Myelom
• benigne Osteolysen
• musculoskeletal manifestations of sarcoidosis
• skeletale Manifestationen der Langerhanszell-Histiozytose
• Sarkoidose der Kalotte

und weiter:

• Enchondroma protuberans
• skelettale Tuberkulose
• vertebral sarcoidosis
• Sarkoidose Kniegelenk