Brucellosis is a common zoonosis worldwide, yet large-scale pediatric data are scarce. This nationwide multicenter study from Türkiye, a highly endemic country, aimed to characterize pediatric brucellosis and identify independent risk factors for complications, relapse, and hospitalization. A retrospective cohort was conducted across 32 hospitals between January 2019 and June 2024. Children aged 0-18 years with confirmed brucellosis were included. Data were analyzed by multiple backward logistic regressions, with Firth penalization for the complication and relapse models. A total of 1052 children were included (median age 12 years; 69.9% male). Complications occurred in 87 patients (8.3%), most frequently osteoarticular (spondylitis, sacroiliitis, and osteomyelitis), whereas neurobrucellosis was rare (0.9%); relapse occurred in 34 patients (3.2%). Complications were independently associated with headache (adjusted OR 3.566, 95% CI 1.861-6.637), arthralgia/arthritis, culture positivity, night sweating, and myalgia. Relapse was independently associated with female sex (adjusted OR 3.675, 95% CI 1.617-8.568), whereas treatment compliance was protective (adjusted OR 0.254, 95% CI 0.092-0.857). Hospitalization (34.1%) was independently associated with headache, diarrhea, hepatomegaly, lymphadenopathy, fever, elevated CRP, and lower hemoglobin, whereas diagnosis through household contact screening was protective. Conclusion: Pediatric brucellosis in Türkiye generally follows a favorable course, with low complication and relapse rates. Readily identifiable musculoskeletal and constitutional symptoms at presentation may help predict complicated disease, while treatment adherence remains the key determinant of relapse. Early detection through household contact screening may reduce disease burden in endemic regions. What is Known: • Brucellosis is a common zoonosis with limited pediatric data worldwide. Early detection and treatment adherence are critical for favorable outcomes. • Complications and relapse are recognized but poorly defined in children What is New: • This is one of the largest nationwide pediatric brucellosis cohorts reported to date, including 1052 children. Household contact screening shown protective against hospitalization. • Treatment adherence, rather than disease severity or complications, was the key determinant of relapse in pediatric brucellosis.

Ureteral entrapment within the sacroiliac joint is an exceedingly rare anatomical phenomenon. To date, 6 cases have been documented in the literature: 1 cadaveric and 5 clinical reports. Among the clinical cases, 3 followed high-energy pelvic trauma, while 2 were nontraumatic. We report the third nontraumatic clinical case (and seventh case overall) in a 77-year-old woman presenting with chronic lower back pain. Computed tomography intravenous pyelography revealed focal entrapment of the right ureter at the level of the sacroiliac joint due to advanced degenerative sacroiliitis. Despite a 10-12 hours delay in contrast excretion, the patient was urologically asymptomatic with stable renal function. Unlike previous nontraumatic cases requiring surgical intervention or nephrostomy, this patient was managed conservatively.

Adolescents commonly present with chronic back and knee pain, and distinguishing mechanical from inflammatory causes is a frequent challenge in general and pediatric practice. Juvenile spondyloarthritis (jSpA) is a chronic inflammatory disease affecting joints, entheses, and potentially the axial skeleton that may require prolonged immunosuppression to prevent structural joint damage. Generalized joint hypermobility (GJH) and hypermobility spectrum disorder (HSD) can present with overlapping musculoskeletal symptoms, including chronic joint pain and back stiffness, and may therefore be mistaken for inflammatory disease. Sacroiliac joint bone marrow edema on magnetic resonance imaging (MRI), although an important feature of axial spondyloarthritis, may also be seen in healthy individuals, athletes, postpartum women, and mechanically stressed joints, particularly when interpreted without adequate clinical correlation. This case report and brief review aim to illustrate how GJH can mimic jSpA and how overinterpretation of sacroiliac MRI findings may lead to unnecessary immunosuppression in adolescents. A 17-year-old male from Bangladesh presented for an independent pediatric rheumatology evaluation after a prior diagnosis of jSpA based on reported sacroiliac MRI abnormalities, partial response to nonsteroidal anti-inflammatory drugs (NSAIDs), and intermittent gastrointestinal symptoms. His inflammatory markers were persistently normal, HLA-B27 testing was negative, and his back pain lacked inflammatory features. Examination demonstrated GJH with a Beighton score of 7/9. Repeat independent sacroiliac MRI was normal, and knee MRI showed a partial anterior cruciate ligament injury with bone contusion, supporting a mechanical etiology. Genetic testing for heritable connective tissue disorders was negative. Expert consultation, including review by specialists affiliated with the Ehlers-Danlos Society and an independent pediatric rheumatologist at the National University Health System in Singapore, favored generalized HSD over jSpA. Structured physiotherapy and conservative rehabilitation led to complete symptom resolution without immunosuppressive therapy. This case highlights the risk of overdiagnosing spondyloarthritis when nonspecific sacroiliac MRI findings are prioritized over the clinical pattern, laboratory data, and mechanical risk factors. GJH should be systematically assessed in adolescents with chronic musculoskeletal pain, especially when inflammatory markers are normal and symptoms are predominantly activity-related.

Objectives: To evaluate the real-world diagnostic and therapeutic impact of repeat sacroiliac joint magnetic resonance imaging (SIJ MRI) in patients undergoing assessment for axial spondyloarthritis (axSpA). Methods: This retrospective study included patients who underwent at least two SIJ MRI examinations from January 2010 to January 2026 at a single tertiary center. Demographic, clinical, laboratory, and imaging data were extracted from electronic medical records. MRI findings were classified according to Assessment of SpondyloArthritis International Society (ASAS) definitions. Changes between MRI1 and MRI2, diagnostic reassessment, treatment modification, and factors associated with diagnostic change were analyzed. Results: A total of 229 patients were included. The median interval between MRI examinations was 34 months. Among patients with initially negative or suspicious MRI findings, 13.0% converted to MRI-positive status on MRI2, whereas 44.8% of those with positive MRI1 findings regressed to negative or suspicious categories. Bone marrow edema (BME) was less frequent on MRI2 than MRI1 (38.0% vs. 50.2%, p = 0.003), while fat metaplasia (9.6% vs. 3.1%, p < 0.001) and sclerosis (34.9% vs. 26.6%, p = 0.006) were more common. Repeat MRI was associated with diagnostic reassessment in 41 patients (17.9%) and treatment modification in 27 patients (11.8%). In multivariate analysis, MRI1 BME positivity (OR 3.13, 95% CI 1.47-6.63, p = 0.003) and higher CRP levels (OR 1.06, 95% CI 1.01-1.11, p = 0.017) were independently associated with diagnostic reassessment. Conclusions: In routine clinical practice, repeat SIJ MRI was associated with diagnostic reassessment and treatment modification in a subset of patients undergoing evaluation for axSpA. Diagnostic reassessment was more frequently observed in patients with baseline inflammatory MRI findings and elevated inflammatory markers.

Multifocal skeletal tuberculosis is an uncommon manifestation of osteoarticular tuberculosis characterized by noncontiguous involvement of multiple skeletal sites. When associated with a mass-like pulmonary lesion, it may closely simulate disseminated malignancy. We report a 26-year-old immunocompetent male presenting with progressive neck stiffness, fever, cough, weight loss, and dysphagia. Imaging demonstrated a large right upper lobe mass with internal air bronchograms and associated centrilobular tree-in-bud nodules, along with multifocal destructive lesions involving the cervical, thoracic, and lumbar spine, sternum, sacroiliac joint, and pelvic bones. Extensive posterior-element involvement was present, with associated prevertebral, paraspinal, and epidural soft-tissue collections resulting in early spinal cord compression. Laboratory evaluation revealed elevated inflammatory markers, a strongly positive Mantoux test, and negative HIV serology. Bronchoalveolar lavage was negative for malignancy and acid-fast bacilli. Histopathological examination of a CT-guided biopsy demonstrated granulomatous inflammation with Langhans-type giant cells, while GeneXpert MTB detected Mycobacterium tuberculosis, confirming the diagnosis. The constellation of a pulmonary mass and multifocal destructive skeletal lesions initially raised strong suspicion for disseminated metastatic disease. This case highlights an uncommon radiologic phenotype of tuberculosis that closely mimics malignancy and underscores the importance of maintaining a high index of suspicion and obtaining early tissue diagnosis to facilitate appropriate management.

Sarcoidosis is a chronic granulomatous, multisystem disease of uncertain etiology that affects various organ systems, although musculoskeletal involvement is rarely the dominant feature. We present the case of a woman in her 50s with a history of pulmonary sarcoidosis who developed new lower back and hip pain. Magnetic resonance imaging demonstrated an asymmetric soft-tissue mass in the ligamentous left sacroiliac joint, along with osseous involvement of the sacrum and ilium. These findings were suspicious for malignancy. An 18F-FDG PET/CT subsequently confirmed FDG-avid disease in this soft-tissue mass and the surrounding bone. However, a CT-guided biopsy of the lesion revealed non-caseating granulomas. This case highlights a rare presentation of skeletal sarcoidosis with an extraosseous mass, a diagnostic pitfall that can closely mimic malignancy or inflammatory sacroiliitis.