<div></div><div>Key Messages:</div><div>The specificity of our cases is their different presentations. The first
case and the third case simulated bone tumors. The second case had the
aspect of spondylodiscitis with soft tissue involvement, which to our
knowledge have not been reported previously, and with simulated
infectious spondylodiscitis.</div><div>Introduction:</div><div>The acronym SAPHO (synovitis, acne, pustulosis, hyperostosis, and
osteitis) includes a group of diseases with similar osteoarticular
manifestations and skin conditions [1,2]. The incidence is thought
to be less than 1/10 000, with the highest occurrence in children and
young adults [3,4]. There are no validated diagnostic criteria and
the diagnosis is based on clinical and radiological findings. When
atypical sites are involved and there are no skin lesions, the diagnosis
may be difficult to be differentiated from other diagnoses, especially
bone tumors, and infectious disease. Herein we present different cases
where the diagnosis was not easy to make.</div><div>Case History:</div><div>Case 1: A 46-year-old woman presented with eight months of cervical pain
history. She had selective pain upon palpation at the cervical spine.
Blood analysis was normal. Cervical Spine X-ray revealed osteosclerosis
of the C5 vertebral body with the aspect of an ivory vertebra which was
confirmed on the cervical scanner (Fig. 1). The spinal magnetic
resonance imaging (MRI) showed an abnormal signal on C5 and C6 with a
hypointense signal on T1 and T2 and a hyperintense signal on T2 Short TI
Inversion Recovery (STIR) and post-contrast enhancement. Bone metastasis
was suspected. A thoracoabdominal pelvic (TAP) tomography was performed
searching for primitive tumors and did not found any suspect lesion, but
showed sclerosis and hyperostosis
of the manubrium and fusion on edges of sternocostal joints. There was
not sacroiliitis. We completed by bone scintigraphy of the whole body,
showing increased uptake in the sternoclavicular articulations with a
characteristic ”bullhead” appearance. SAPHO syndrome was diagnosed and
treatment with diclofenac was initiated, with real clinical improvement.
The control X-ray showed the appearance of para-vertebral ossification
with the aspect of an ivory C4, C5 and C6 vertebra (Figure 1b).</div><div>Case 2: A 61-year-old woman presented with complaints of the thoracic
and lumbar spine. Clinical examination showed a stiffness of the lumbar
spine. The C-reactive protein (CRP) and erythrocyte sedimentation rate
(ESR) were elevated to 14 mg/L and 83 mm respectively. Conventional
radiography showed a narrowing of the intervertebral discs D5-D6 and
D6-D7. Spine MRI showed spondylodiscitis in D3-D4, D4-D5, D5-D6, D6-D7,
and L1-L2 and soft tissue involvement, simulating infectious
spondylodiscitis (Fig. 2). All infectious investigation was negative
(chest X-Ray, cytobacteriological examination of the urine, Tuberculin
Skin Test, Wright test). A biopsy was performed showing unspecific
inflammation. As the patient was a consumer of unpasteurized milk and
according to the MRI findings, the diagnosis of brucellar
spondylodiscitis was first evocated and treatment with Rifadin and
doxycyclin was decided upon. After six months of treatment, no clinical
improvement has been noted. CRP and ESR remained elevated. No bone
reconstruction has been noticed in the plain radiography. So a second
MRI was performed and showed the stabilization of the original lesions
and the appearance of a new lesion in L4-L5. A second vertebral biopsy
was performed and was sterile. The diagnosis of SAPHO was then suspected
and bone scintigraphy was performed showing uptake in the chondrosternal
articulations and D4 to D7 vertebrae, corresponding to the diagnosis of
SAPHO. The patient did not respond to four classes of NSAIDs, so the
decision was to switch to Etanercept with clinical and biological
improvement and unchanged lesions in MRI after 3 months.</div><div>Case 3: A 46-year-old man followed at the department of carcinology for
lung adenocarcinoma. Staging for metastatic disease, a TAP tomography
was performed and showed osteosclerosis of vertebral bodies of D8 to D12
and L4 with paravertebral ossifications (Fig. 3a) and bilateral
osteosclerosis in the sacroiliac joints (Fig. 3b). Among the relevant
history of the patient, we found mechanic low back pain lasting for 20
years. As malignancy could not be eliminated, an MRI was performed
showing bilateral sacroiliitis (Fig. 3c) and abnormal signal in the D4
to D11 vertebrae. Bone scintigraphy showed increased uptake in the
manubrium, D8 to D11 vertebrae, sacroiliac joints, right collarbone, and
skull. The diagnosis of SAPHO was made and the patient was treated by
diclofenac. Control by a TAP tomography was performed, showing ankyloses
of sacro-iliac joint (figure 4).</div><div>Discussion:</div><div>SAPHO syndrome was first described by the French Society of Rheumatology
in 1987 as a group of musculoskeletal manifestations that can or cannot
be associated with dermatologic lesions [1]. The osteoarticular
manifestations include synovitis, hyperostosis, and osteitis. The skin
manifestations typically are palmoplantar pustulosis and acne. They can
either precede (40-60%), occur simultaneously (30%), or after the
start of the osteoarticular lesions (32-60%) [5,6]. At least 15%
of adult patients may never have skin manifestations. The diagnosis of
SAPHO syndrome is not difficult when the typical osteoarticular lesions
are located in characteristic target sites. The diagnosis is more
difficult if atypical sites are involved and there is no skin disease.
In our cases, no patient had dermatologic manifestations. The
osteoarticular involvement is generally insidious in onset [7], like
in our third patient where the diagnosis was fortuitous. Although the
sternoclavicular involvement is the most common localization, other
bones in the axial or peripheral skeleton may be involved. The spine is
the second most common site in the disease being involved in up to
one-third of cases, most frequently in the thoracic spine, followed by
the lumbar and cervical spine [8]. Spinal involvement is usually
segmental, most commonly affecting a single vertebra, but occasionally
affects up to four lesions [8]. All our patients had more than one
vertebra affected, and our third patient even had five vertebrae
affected. There is frequent involvement of the soft tissues but abscess
and epiduritis are usually not seen [8]; however, our second case
presented infrequent liquid paravertebral masses, which to the best of
our knowledge have not been reported before. The presence of liquid
masses makes the differential diagnosis with an infectious disease more
difficult, especially knowing that an infectious theory involving
Propionibacterium Acnes has been proposed [9]. P Acne activates
innate immune response through Toll-like receptors [10]. It can
persist in a latent form in bone cells and to enhance IL1ß production by
skin and bone cells leading to dermatologic and osteoarticular lesions
[11]. Sacroiliitis of SAPHO is observed in 13% to 52% of cases
[12,13], it is more frequently unilateral and is characterized by a
predominance of hyperostosis and sclerosis in the iliac side [7].
Our third patient had bilateral sacroiliitis. MRI is the most sensitive
imaging technique in evaluating soft-tissue swelling, synovial reaction,
and intra-articular effusion and synovial reaction in SAPHO syndrome
[14]. Bone scintigraphy can be very useful because it not only shows
increased uptake in the affected sites but also reveals silent lesions
[15]. The most frequent localization is the anterior chest wall,
especially the characteristic appearance of bull’s head, as seen in the
first case. Bone biopsy does not reveal specific lesions but it helps to
exclude malignant and infectious aetiologies [7]. Most patients are
treated in a symptomatic way with nonsteroidal anti-inflammatory drugs
(NSAIDs) and analgesics. The role of antibiotics remains unclear.
Conventional disease-modifying anti-rheumatic drugs (DMARDs) have their
place. In the refractory cases, anti-TNF alpha agents are used. A good
response is frequently obtained like in our second case [16]. The
prognosis of SAPHO syndrome is considered to be relatively good
[12]. But the ignorance of the syndrome and the fear of a bone tumor
or an infectious disease are a major source of antibiotics and biopsy.</div><div>In conclusion, the diagnosis of SAPHO syndrome is not difficult when
typical bone lesions are associated with typical skin manifestations.
The diagnosis is much more difficult if the osteoarticular sites are
atypical, especially if the patients are free of skin disease. In those
cases, imaging findings could facilitate differentiating SAPHO syndrome
from other diseases.</div><div>Author Contributions:</div><div>Author 1: Design, literature search, manuscript preparation, manuscript
review</div><div>Author 2: Design, literature search, manuscript preparation, manuscript
review</div><div>Author 3: manuscript preparation, manuscript review</div><div>Author 4: manuscript preparation, manuscript review</div><div>Author 5: manuscript review</div><div>Author 6: manuscript review</div><div>References:</div><div>1 Chamot AM, Benhamou CL, Kahn MF, Beraneck L, Kaplan G, Prost A. Le
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