Teaching Case

A 55-year-old woman presented with general arthralgia and axial pain since many years. Clinical inspection revealed palmoplantar pustulosis.

Chest radiography showed sclerosis of the medial aspect of the left clavicle (Figure 2).

CT confirmed osteosclerosis and periosteal reaction at the left clavicle. Erosions were seen at the sternoclavicular and costosternal joints with ligamentous ossification of the left costoclavicular ligament (Figure 3a-b).

MRI of the sternoclavicular joints revealed a mixture of sclerosis and bone marrow oedema (Figure 4a-c). After administration of gadolinium contrast, there was also enhancement of the left clavicle (Figure 4d).

SAPHO is an acronym that stands for synovitis, acne, pustulosis, hyperostosis and osteitis.

The hallmark of the skin manifestations is palmoplantar pustulosis and acne [1].

SAPHO syndrome tends to involve the axial skeleton and the anterior chest wall, especially the sternoclavicular joint, with clavicular involvement typically starting at the medial aspect [2]. Spinal involvement is usually monovertebral, with the thoracic spine being most frequently affected [3]. Sacroiliitis is also sometimes seen. Peripheral joints in the form of a mono- or polyarthritis can also be affected, but to a lesser extent [4].

Its pathogenesis is still not completely understood. There is an association with HLA-B27 and different pathogens were isolated from different bone sites and pustules in the skin. The most probable hypothesis is that it is caused by autoimmune reactions in genetically predisposed individuals triggered by some infectious agent [5].

Patients present with pain, swelling, and limitation of movement, most often in the anterior chest wall. In many patients, there is a considerable delay in the correct diagnosis [1].

In children and adolescents, a similar condition called chronic recurrent multifocal osteomyelitis (CRMO), more commonly involves the long bone metaphyses and clavicles [1].

The imaging features are dominated by hyperostosis, osteitis and synovitis, arthritis, and chronic inflammatory bone disease. Osteitis consists of inflammation of the medullary bone, which manifests as osteosclerosis on conventional radiography. The term hyperostosis is used to designate chronic periosteal reaction and cortical thickening leading to bone hypertrophy. Radiography is usually the initial modality and can reveal sclerosis and periosteal reaction in advanced disease, but it is less sensitive for early detection. CT scan is the preferred modality to demonstrate osteosclerosis and/or hyperostosis, erosions, and ligamentous ossifications. MR imaging on the other hand, is best suited for demonstration of inflammatory changes and bone marrow oedema using fluid-sensitive sequences. Whole-body MRI is recommended for the evaluation of multifocality and asymptomatic lesions [6, 7].

The treatment remains a challenge. It includes administration of nonsteroidal anti-inflammatory drugs, corticosteroids, methotrexate, and tumour necrosis factor alfa inhibitors. Except for a minority of patients who have a self-limited course, most of them have either a relapsing-remitting course or a chronic indolent disease pattern [5].

Written informed patient consent for publication has been obtained.