Brucellosis is a zoonotic infection, endemic in rural areas. It is caused by Brucella species, which are transmitted through the intake of unpasteurized dairy products and contact with infected animals. Sacroiliac joint involvement is common in brucellosis and typically presents as unilateral sacroiliitis. Contrarily, bilateral sacroiliitis is less typical and may mimic tuberculosis, pyogenic infection, or inflammatory spondyloarthropathy. We report a case of a 19-year-old man who presented with a one-month history of bilateral buttock pain radiating to the legs and a 2-week history of fever, chills, rigors, and febrile diaphoresis. He reported unpasteurized milk intake. Physical examination revealed bilateral sacroiliac joint tenderness, and Patrick's and Gaenslen's provocation tests elicited pain in both sacroiliac joints. Laboratory findings showed leukocytosis, elevated CRP, and ESR. Standard agglutination testing was positive for anti-Brucella antibodies, and MRI confirmed bilateral sacroiliitis, along with erosive changes and marrow edema. A diagnosis of brucellosis complicated by bilateral sacroiliitis was proposed. The patient was started on doxycycline, co-trimoxazole, and gentamicin. Gentamicin was used for 22 days, while doxycycline and co-trimoxazole were continued for a total planned duration of 13 weeks. During follow-up visits (day 15 and day 45), the patient demonstrated clinical improvement, evident by laboratory parameters, pain improvement, no fever, difficulty walking, and medication-related adverse effects. This case emphasizes that clinicians in endemic areas must consider brucellosis as a differential diagnosis in patients with bilateral lower back or buttock pain. MRI findings and serology testing are useful in early recognition. While blood cultures, PCR, and biopsy are necessary for definitive diagnosis.

SAPHO syndrome is a rare autoinflammatory disorder characterized by synovitis, acne, pustulosis, hyperostosis, and osteitis. Although musculoskeletal and dermatologic manifestations are well recognized, extra-articular involvement remains uncommon, particularly muscular inflammation. We report the case of a 17-year-old male who presented with severe inflammatory low back pain and extensive nodulocystic acne for which he took escalating doses of isotretinoin. Clinical examination demonstrated positive sacroiliac stress tests, proximal muscle myopathy, and dermatologic evaluation confirmed acne conglobata. Laboratory testing revealed markedly elevated inflammatory markers. Magnetic resonance imaging of the sacroiliac joints showed bilateral asymmetric active sacroiliitis, fulfilling clinical criteria for Axial Spondyloarthritis. The infectious and autoimmune workup was negative. The patient responded favorably to isotretinoin withdrawal and immunosuppressive therapy, with sustained remission following steroid withdrawal. This case describes a rare and severe isotretinoin-associated inflammatory myopathy in SAPHO syndrome, highlighting the need to expand the differential diagnosis of myopathy in SAPHO syndrome. It is imperative to exercise caution when prescribing isotretinoin to patients with SAPHO syndrome.

The sacroiliac joint (SIJ) is a critical anatomic structure that connects the axial skeleton with the lower limbs. Compared with its adult counterpart, the pediatric SIJ exhibits unique anatomic features, and imaging evaluation may then present significant challenges due to overlapping features between normal developmental manifestations, anatomic variants, and true pathologic conditions. Two frequently observed developmental findings can resemble pathologic conditions: subchondral irregularities and subchondral flaring. These are commonly seen on MR images of the developing pelvis. A diverse range of anatomic variations has been documented in both the cartilaginous and ligamentous components of the SIJ. Though overall innocuous, some variations are linked to mechanical overload and pain. True sacroiliitis can arise from inflammatory, infectious, or traumatic causes. Inflammatory conditions may exhibit similar imaging characteristics and are best differentiated through MRI. The presence of unilateral sacroiliitis should prompt consideration of an infectious cause, with imaging indicators such as capsular edema and abscess formation suggesting infection. Traumatic injuries to the SIJ are uncommon in children and usually occur in the context of high-energy trauma. Mechanical overload or repetitive stress in the pediatric population can result in bone marrow edema in the weight-bearing regions of the SIJ and, less commonly, in sacral stress fractures, most often involving the sacral ala. It is crucial to accurately differentiate these imaging features to avoid functional impairments, morbidity, and unnecessary interventions. The authors aim to enhance radiologists' understanding of the pediatric SIJ by examining its unique anatomic characteristics, key imaging features, and pertinent differential diagnosis. [©] RSNA, 2026 Supplemental material is available for this article.

Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease characterized by autoantibody production and immune complex deposition. Antiphospholipid syndrome (APS) is frequently associated with SLE and is characterized by arterial or venous thrombosis and pregnancy morbidity in the presence of persistent antiphospholipid antibodies. The coexistence of ankylosing spondylitis (AS) with SLE and APS is extremely rare. A 38-year-old woman was admitted to our clinic with gangrene of the right fifth toe and swelling of both knees. She had a previous diagnosis of AS based on inflammatory low back pain and radiographic evidence of bilateral Grade 4 sacroiliitis. Laboratory investigations revealed positive antinuclear antibody, anti-double-stranded DNA, and antiphospholipid antibodies, including lupus anticoagulant and anti-cardiolipin IgG. Renal biopsy performed due to proteinuria demonstrated mesangioproliferative lupus nephritis. Based on clinical, laboratory, and histopathological findings, the patient was diagnosed with coexisting AS, SLE, and APS. Considering the coexistence of these autoimmune diseases and the patient's previous exposure to anti-tumor necrosis factor therapy, treatment with the interleukin-17 inhibitor secukinumab was initiated. The patient showed significant improvement in inflammatory back pain and arthritis during follow-up. To our knowledge, this is one of the rare reported cases of coexistence of AS, SLE, and APS treated with secukinumab.

Brucellosis is a zoonosis acquired direct contact with infected animals or by consumption of unpasteurized animal by-products. The most common complications involve the musculoskeletal system, such as sacroiliitis or vertebral osteomyelitis. However, skin and soft tissue involvement is uncommon, and cervical abscess are rarely reported. We report the case of a 19-year-old male patient, with no medical history, from the metropolitan region of Caracas, Venezuela, with no history of travel or direct contact with farm animals, but regular consumption of cheese. In July 2024, he presented with undulating fever, hypor1exia and general malaise. One month later his fever intensified, preceded by chills, followed by the development of a painful, erythematous, warm swelling in the anterior neck, which evolved into an abscess requiring drainage. Purulent material yielded Brucella abortus biovar 1 confirmed by Polymerase Chain Reaction (PCR). The patient received Rifampicin and Doxycycline with full recovery. To our knowledge, this is the first recorded case of human brucellosis with this presentation in Venezuela, and the first reported case of cervical abscess caused by Brucella abortus. These findings underscore the importance of maintaining epidemiological surveillance of brucellosis and strengthening quality control and hygiene measures throughout the dairy production and distribution chain.