Background information
The acronym “SAPHO” describes the key symptoms of “Synovitis”, “Acne”, “Pustulosis”, “Hyperostosis” and “Osteitis”. The term “Skibo disease” (skin and bone) is also derived from the heterogeneous coexistence of skin and bone findings. The disease is an autoinflammatory disease associated with cutaneous involvement and chronic non-bacterial osteomyelitis. The diagnostic criteria are:
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multifocal sterile osteomyelitis with or without pustular skin disease,
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arthritis and pustular dermatosis, and
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osteomyelitis and pustular dermatosis or psoriasis.
The following forms of SAPHO syndrome are distinguished:
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chronic recurrent multifocal osteomyelitis (CRMO) in two-thirds of cases,
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spondyloarthritis hyperostotica pustulopsoriatica in almost one-third of cases (pustulosis palmoplantaris, sternoclavicular hyperostosis, spinal lesions) and
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rarely abortive forms (ACW syndrome = anterior chest wall syndrome, SCCH = sternoclavicular hyperostosis, acne-CRMO, acne-spondylitis).
Chronic recurrent multifocal osteomyelitis (CRMO) usually manifests outside of SAPHO syndrome with synchronous or metachronous osteomyelitis at the metaphyses of the long bones, at the thoracolumbar vertebral bodies and clavicles. Pustulosis palmoplantaris is present in 60% of cases. Pathogens usually cannot be isolated; anaerobic, hypovirulent skin germs are discussed as the cause.
Whether SAPHO syndrome should be classified as a seronegative spondyloarthropathy is a matter of controversy. The spondylarthropathy group comprises these entities:
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ankylosing spondylitis (Bechterew's disease),
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psoriatic arthropathy,
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enteropathic arthritis (Crohn's disease, ulcerative colitis),
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reactive (post-infectious) arthritis and
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undifferentiated spondyloarthritis.
Learning points
In cases of multifocal joint and spinal lesions, the history should be extended to cover evidence of skin involvement. Inflammatory lesions of the skeletal system are often detected earlier by MRI than by radiography. Imaging plays an important role in early diagnosis of inflammatory skeletal diseases.
