The patient presented with continuous pain in the left hip, which had been treated with physiotherapy for about 2 years. CRP was 4.2 mg/dl, other haematologic or biochemical parameters were normal. No skin rashes had been present. On external radiographs of the left hip, a "bone tumour" had been reported (images unavailable).
An MRI of the pelvis showed T2 hyperintense and T1 hypointense signal alterations in the left proximal femur, and to a lesser extent, in the 5th lumbar vertebra (Fig. 1a). The dorsal femoral trochanteric region and neck appeared thickened with unsharp borders. After contrast administration, there was intense patchy enhancement without demarcation of liquid zones (Fig. 1b). Soft-tissue oedema, but no mass could be seen in the neighbourhood. CT showed cortical bone thickening with irregular contours and multiple, partly confluent osteolytic foci (Fig. 2). A bone scintigram showed increased blood pool activity and late radionuclide deposition in both known regions, and revealed a third lesion in the corpus sterni (Fig. 3). A biopsy of the distal trochanteric region was obtained and showed a highly vascularised, predominantly inflammatory process with bone resorption and apposition. Malignancy could be excluded. Molecular biologic studies and cultures were negative for bacteria. The diagnosis of CRMO was established.
CRMO is an inflammatory condition involving one or, more typically, multiple bones. It has been first described in the early nineteen-seventies and predominantly affects children and adolescents. Occurrence in adults is however not unknown. There seems to be a female predilection of 2:1 [1]. The aetiology of CRMO has not been fully explained. An association with autoimmune diseases, e.g. Crohn's or psoriasis has been well documented. Newer studies have postulated a genetic component suggesting interleukin-1 as a key factor in the pathogenesis [2]. There is also a close link with the SAPHO syndrome, a variety of hyperostotic skeletal disorders occurring together with synovitis and dermatoses, such as acne or pustulosis. By some authors, SAPHO is regarded as the adult form of CRMO and vice versa [3].
The onset of clinical symptoms is often insidious and there may be exacerbations and remissions. Fever is present in only half of cases, laboratory tests may be normal, and pain is typically localised, even in multifocal disease. The three most common sites at initial presentation are the lower extremities, the spine and the pelvis. As in SAPHO, the bones of the anterior thoracic wall (clavicles, sternum, ribs) can also be affected [1].
The radiographic and histopathologic features of CRMO are similar to chronic infectious osteomyelitis, often with predominant sclerosis in long-standing cases, but large abscesses, fistulous tracts and sequesters are usually absent. No pathogens can be isolated from the affected tissues (abacterial osteomyelitis). Biopsy must always be performed, for there is a broad differential diagnosis to the imaging appearance, which also includes malignant disease (see below). Radionuclide bone scans are traditionally prescribed to determine the extent of the disease [4]. In recent times, MRI is increasingly used for this purpose [5]. MRI is also the most suitable imaging study to monitor disease activity during and after treatment [1].
CRMO is generally a self-limited disease, however up to 50% of patients may experience skeletal growth disturbances or deformities later in life. The treatment is not standardised. Though antibiotics have no impact on the course of the disease, a trial treatment is sometimes necessary. In abacterial osteomyelitis, NSAIDs are the mainstay of treatment. Bisphosphonates and TNFa antagonists are used in more severe forms [3]. In the present case, the patient didn't respond well to NSAIDs and was treated with etoricoxib and a single dose of bisphosphonates. Fig. 4 shows an MRI of the pelvis obtained 2 years after the initial diagnosis.
Chronic recurrent multifocal osteomyelitis (CRMO)
Based on the provided imaging (including MRI, CT, plain radiographs, and radionuclide bone scans), the following features are observed:
• An abnormal signal or density change is visible in the left iliac bone or near the femur/trochanteric region, manifested by local bone structural thickening, sclerosis, or mixed signal intensity.
• On MRI, T2-weighted sequences show relatively high signal areas with some degree of bone marrow edema, while T1-weighted sequences demonstrate relatively decreased or heterogeneous signals.
• CT reveals significant bone sclerosis and proliferative changes in the lesion area, with scattered thickening of bone trabeculae, but without extensive bone destruction or large abscess/sequestrum formation.
• Radionuclide bone scan may indicate multifocal or localized metabolic increases. Based on current imaging, no extensive abnormalities in other regions are noted (if other lesions are suspected, further evaluation is needed).
Considering the patient is a 25-year-old female with persistent hip joint pain, mildly elevated inflammatory markers, and radiographic findings of bone sclerosis and localized edema, the following diagnoses should be contemplated:
1) Chronic Recurrent Multifocal Osteomyelitis (CRMO):
• Commonly seen in children and adolescents, but also occurs in young adults, typically presenting with chronic, recurrent pain.
• Imaging findings resemble chronic osteomyelitis but without bacterial evidence, often showing varying degrees of bone sclerosis, bone marrow edema, and multifocal lesions.
• May be associated with SAPHO syndrome or autoimmune diseases.
2) Infectious Osteomyelitis (bacterial):
• Usually presents with more pronounced inflammatory signs (significantly elevated CRP, high white blood cell count, etc.), along with notable bone destruction, potential abscesses, or sequestra.
• Although the CRP level is slightly elevated in this case, it does not fit the typical profile of bacterial infection. Additionally, the prolonged clinical history and imaging findings are atypical for an acute infectious process.
3) Bone Tumor or Tumor-like Lesions (e.g., Giant Cell Tumor, Osteosarcoma):
• Malignant tumors generally exhibit more extensive bone destruction or a substantial soft tissue mass.
• Histopathological biopsy is key to excluding malignancy.
4) Other Rare Bone Diseases (e.g., Langerhans Cell Histiocytosis):
• May also present with mixed lytic-sclerotic changes, but often have more distinctive clinical or morphological features.
Taking into account the patient's age, clinical presentation (persistent hip pain without marked acute inflammatory symptoms), imaging findings (primarily bone sclerosis and osteomyelitis-like changes lacking typical abscess/sequestrum), and laboratory tests (slightly elevated CRP with other parameters largely normal), the most likely diagnosis is: Chronic Recurrent Multifocal Osteomyelitis (CRMO).
If there is any doubt, a biopsy of the lesion can be performed to rule out malignancy and confirm the exclusion of bacterial osteomyelitis.
Treatment Strategy:
• Medications: NSAIDs (non-steroidal anti-inflammatory drugs) are the first-line treatment. In more severe cases or where NSAIDs are insufficient, consider bisphosphonates, TNF-α inhibitors, or other advanced immunomodulators.
• Other Management: In situations where infection cannot be definitively ruled out, short-term antibiotic therapy may be used early on, though prolonged antibiotic use has no clear benefit once infection is excluded.
• Follow-up: Regular MRI or bone scans are recommended to monitor lesion activity, treatment response, and disease progression.
Rehabilitation/Exercise Prescription (FITT-VP Principle) Example:
1) Frequency (F): Engage in light to moderate exercise 3–4 times per week initially. If pain and inflammation improve, gradually increase to 4–5 times per week.
2) Intensity (I): Begin with exercises placing minimal stress on the joints (such as water walking or cycling), avoiding high-impact or heavily weight-bearing activities. As symptoms and inflammation subside, gradually increase resistance training intensity.
3) Time (T): Start with 20–30 minutes per session, and increase by 5–10 minutes every 2 weeks based on tolerance, avoiding excessive fatigue.
4) Type (T): Focus on protecting joints, promoting bone blood circulation, and maintaining muscle strength through aquatic therapy, low-intensity muscle strengthening, and stability training (core or hip stabilizing exercises).
5) Progression (P): With symptom relief and functional improvement, progressively incorporate weight-bearing exercises or light running, monitoring closely for any recurrence of pain or inflammation.
6) Volume & Individualization (V): Tailor the exercise volume to the patient's overall fitness, bone condition, and pain tolerance, avoiding overtraining.
Precautions:
• CRMO can flare up periodically, so remain alert to any worsening hip pain or new joint discomfort during exercise.
• If pain intensifies or significant swelling/inflammation appears, seek medical evaluation promptly and adjust the exercise regimen as necessary.
• If long-term use of potent medications (TNF-α inhibitors, bisphosphonates, etc.) is indicated, closely monitor bone density and potential systemic side effects.
Disclaimer: This report provides a reference analysis based on imaging and preliminary clinical information and does not substitute for an in-person consultation or professional medical judgment. If you have any questions or if symptoms change, please consult a specialist or visit a hospital.
Chronic recurrent multifocal osteomyelitis (CRMO)
