Familiar Mediterranean fever mimicking septic arthritis: distinguishing with diffusion weighted imaging

Familial Mediterranean fever with pseudo-septic arthritis: A case report and review of the literature

Familial Mediterranean fever (FMF) is a hereditary auto-inflammatory disease resulting from mutations of the MEFV gene. The disease is characterised by recurrent attacks of abdominal pain and fever. Most FMF patients develop arthritis at some point in their life usually manifesting as self-limiting monoarthritis. On very rare occasions, arthritis in FMF can mimic septic arthritis (pseudo-septic arthritis) with very similar clinical and laboratory findings. We report a case of a young male patient who presented with recurrent attacks of prolonged monoarthritis. For 2 years, he had undergone multiple admissions and operations for drainage of suspected septic joints. The synovial aspiration showed culture-negative pus with very high synovial white blood cell counts highly suggestive of septic arthritis. The patient was later found to have FMF based on homozygous M694V mutation of the MEFV gene. He was treated with colchicine monotherapy with a quick improvement of arthritis and later good control of his disease. The literature review showed very few case reports with similar presentations, most of which responded well to colchicine. FMF can mimic septic arthritis resulting in unnecessary expensive and invasive interventions and prolonged courses of antibiotics. Pseudo-septic arthritis is usually associated with M694V homozygous mutation and can complicate FMF at any time throughout the disease course. It is important to consider FMF in the differential diagnosis of septic arthritis, particularly with a family history of FMF and in patients from communities with a high prevalence of MEFV gene mutation.

Role of Diffusion Weighted Imaging in Musculoskeletal Infections: Current Perspectives

Accurate diagnosis and prompt therapy of musculoskeletal infections are important prognostic factors. In most cases, clinical history, examination and laboratory findings help one make the diagnosis, and routine magnetic resonance imaging (MRI) is useful to identify the extent of the disease process. However, in many situations, a routine MRI may not be specific enough especially if the patient cannot receive contrast intravenously, thereby delaying the appropriate treatment. Diffusion-weighted imaging (DWI) can help in many such situations by providing additional information, accurate characterization and defining the extent of the disease, so that prompt treatment can be initiated. In this article, we illustrate the imaging findings of the spectrum of musculoskeletal infections, emphasizing the role of DWI in this domain.

KEY POINTS

• Abscess in background cellulitis is detected on DWI. • Infectious tenosynovitis shows diffusion restriction as compared to mechanical tenosynovitis. • Pyomyositis with abscess can be differentiated from diabetic myonecrosis on DWI. • Intraosseous abscess is bright on DWI versus devitalized tissue, sequestrum and air. • DWI can be used to differentiate spine infection from simple Modic changes.

Auto inflammatory syndromes: Diagnosis and treatment

Hereditary recurrent fevers are rare genetic diseases characterized by apparently spontaneous attacks of inflammation. They include familial Mediterranean fever (FMF); tumor necrosis factor (TNF) receptor periodic syndrome (TRAPS); hyperimmunoglobulinemia D syndrome (HIDS); and hereditary periodic fevers related to mutations in the CIAS1 (cold induced autoinflammatory syndrome 1) gene, such as Muckle-Wells syndrome, familial cold urticaria, and CINCA/NOMID (chronic infantile neurological cutaneous and articular/neonatal-onset multisystemic inflammatory disease). Musculoskeletal manifestations are common. They may occur as features of the acute inflammatory attacks or persist for longer periods. Among them, the most common include arthritis of the large and medium-sized joints in FMF and CINCA, arthralgia in HIDS, and myalgia or pseudo-fasciitis in TRAPS. The outcome is usually favorable, although joint destruction may develop in CINCA or at the hip in FMF. The recurrent bouts of fever and accompanying clinical manifestations suggest the diagnosis, which can be confirmed by genetic testing. Among differential diagnoses, infection should be considered routinely. The treatment of the inflammatory attacks is nonspecific. New pathophysiological insights have led to the development of promising maintenance treatments designed to reduce the number and severity of the inflammatory attacks and to diminish the risk of secondary amyloidosis.