Protracted Febrile Myalgia Findings on MRI- A Case Series of 4 Patients

Neta Aviran ¹ Gil Amarilyo ^1,2 Yaniv Lakovsky ³ Jenny Garkaby ^5,7 Rubi Haviv ^2,8 Rotem Tal ^1,4 Shiri Spielman ^1,9 Hamada Mohammad Natour ¹ Yonatan Butbul Aviel ^5,6,7 Harel Liora ^1,2

¹Rheumatology Unit, Schneider Children's Medical Center of Israel, ישראל
²Sackler School of Medicine, Tel Aviv University, ישראל
³Department of Radiology, Schneider Children's Medical Center of Israel, ישראל
⁴Pediatric Day Care Center, Schneider Children's Medical Center of Israel, ישראל
⁵Department of Pediatrics B, Ruth Rappaport Children's Hospital, Rambam Health Care Campus, ישראל
⁶Rheumatology Unit, Ruth Rappaport Children's Hospital, Rambam Health Care Campus, ישראל
⁷The Ruth and Bruce Rappaport Faculty of Medicine, Technion - Israel Institute of Technology, ישראל
⁸Pediatric Rheumatology Unit, Meir Medical Center, ישראל
⁹Rheumatology Unit, Edmond and Lily Safra Children's Hospital, Sheba Medical Center, Tel-Hashomer, ישראל

Objective: Protracted febrile myalgia syndrome (PFMS) is a rare dramatic complication of Familial Mediterranean fever (FMF) which consist of prolonged attack of fever and excruciating myalgia (up to 6 weeks) with normal creatine phosphokinase (CPK) levels. This syndrome may be the first sign of FMF and moreover, the molecular diagnosis of FMF is occasionally unknown at time of presentation. Therefore, unnecessary workup and delay of diagnosis are common. We aimed to describe for the first time the MRI findings of 4 patients with PFMS and their contribution to diagnosis.

Methods: Four patients with PFMS who had MRI data during attack were identified from the electronic database of a 4 tertiary pediatric medical centers. All patients were genetically tested by Sanger sequencing for the 9 most common MEFV mutations. Their clinical, laboratory and imaging data were collected. MRI findings were revised by a musculoskeletal radiologist.

Results: There were 3 females and 1 male patients of median age 7 years. one patient was found to be homozygous for the M694V mutation. In 3 patients, PFMS was the first-ever manifestation of FMF. All patients demonstrated various degrees of myositis although CPK levels were normal.

Conclusion: myositis observed in MRI along with relevant symptoms and normal CPK levels can facilitate the diagnosis of PMFS even without prior genetic or clinical evidence of FMF.