An 8-year-old boy was referred with 5 weeks history of generally feeling unwell with lethargy, intermittent fevers, rash on chest, face, knees and elbows and loss of appetite. Neurological examination revealed proximal muscle weakness in the lower-limbs. Laboratory tests demonstrated leucopenia, elevated transaminases and creatine kinases. Abdominal ultrasonography was normal.
MRI of pelvis and upper thigh was performed. T1 axial, STIR axial and STIR coronal imaging sequences were used. STIR sequences showed diffuse bilateral patchy high signal intensity involving the skeletal muscles.
Juvenile Dermatomyositis is a rare multisystem disorder of children. It is the most common idiopathic inflammatory myopathy accounting for 85 percent of the cases [1]. Autoimmune reaction in response to environmental triggers like a viral infection in genetically susceptible individuals has been proposed [1]. Timely diagnosis and management is of paramount importance to avoid complications and functional disability in children.
Symmetrical proximal muscle weakness is the hallmark clinical manifestation of Juvenile Dermatomyositis. The most common symptom at the disease onset is skin rash (Gottron's and Heliotrope rashes). In a classical presentation like in this case, diagnosis can be made based on the clinical presentation. MRI findings in proximal musculature and skin is a sensitive tool in confirming the diagnosis.
MRI demonstrates inflammatory changes in proximal muscles in the form of high signal intensities on T2 weighted or fat suppressed T2 (STIR) images like in this case. Though clinically Juvenile Dermatomyositis causes symmetric proximal muscle weakness, the muscle involvement can be patchy or asymmetric [2]. In more severe cases, there will be involvement of skin, subcutaneous connective tissue and muscle fascia. T1 weighted images detect muscle atrophy and fatty infiltration in the setting of chronic disease [2]. MRI thereby can accurately demonstrate the intensity and extent of the disease and defines an appropriate biopsy site. Literature review also shows a decline in high signal intensities in patients responding to immunosuppressive treatment. Hence, MRI also demonstrates a role in monitoring disease process [3].
Abnormal MRI signals in muscles characterise myopathies. MRI is a sensitive tool in detecting muscle inflammation, although not specific. The signal changes on imaging needs to be interpreted on the background of the clinical setting.
Juvenile Dermatomyositis
According to the provided MRI images, bilateral proximal muscle groups exhibit hyperintense signals on T2-weighted or STIR sequences, indicating significant muscle inflammation. The lesions appear relatively symmetrical, primarily involving the proximal thigh muscles. In some images, signal enhancement within the muscles can be observed due to inflammation. No obvious muscle atrophy or fatty infiltration is seen, suggesting that the disease is still in the acute or subacute inflammatory stage. Furthermore, there are no extensive lesions noted in the adjacent soft tissues, and the skeletal structure seems to be without significant abnormalities.
Based on the overall clinical presentation (fever, fatigue, characteristic rash, and symmetrical proximal muscle weakness), laboratory findings (leukopenia, elevated transaminases, and creatine kinase), and MRI showing hyperintense signals in proximal muscle groups on T2 and STIR sequences, the most likely diagnosis is:
Juvenile Dermatomyositis (JDM)
Treatment Plan:
Rehabilitation/Exercise Prescription (FITT-VP Principle):
Throughout this process, special attention should be paid to the child’s cardiopulmonary function and skeletal development, avoiding high-impact or excessively intense activities. Regular consultations are essential to adapt the exercise prescription as needed.
This report is a reference-based medical analysis derived from the currently provided information. It cannot replace a face-to-face consultation or further examination by a qualified physician. Please consult an appropriate specialist and combine clinical evaluations for an accurate treatment plan.
Juvenile Dermatomyositis
