[Magnetic resonance imaging of dystrophinopathy that mimics adductor enthesopathy]

To report thigh muscle magnetic resonance imaging (MRI) tests of four Chinese patients with dystrophinopathy with edema changes in adductor longus muscles that mimics adductor enthesopathy.

Four boys, who were from four unrelated families and aged from 5 to 11 years, were investigated because of the clinical manifestations including myalgia or muscle weakness or the incidental findings of elevated serum creatine kinase levels, and were diagnosed with dystrophinopathy by gene test of Duchenne muscular dystrophy (DMD). Their creatine kinase levels were increased from 4 087 IU/L to 32 700 IU/L (Normal range: 75-175 IU/L). The muscle biopsy of three patients all demonstrated a dystrophic pattern including necrosis, regeneration, hypertrophy, atrophy and connective tissue proliferation, with different proportions of dystrophin-negative muscle fibers. The gene test of DMD showed an out-frame deletion of exons in three of the four patients, involving either exons 45 or exons 49-52 deletion or exon 62 duplication, and c.2665 C>T with nonsense mutation in the other one. Muscle MRI tests of the bilateral thighs were performed with T1 weighed sequence and slow tau inversion recovery sequence. The degree of fatty infiltration changes was scored.

MRI of the thigh muscles showed mild to severe fatty infiltration changes in T1 weighed sequence with the total scores from 2 to 13.The most severe fatty infiltration changes were in the long head of biceps femoris and adductor magnus. Obvious hyperintensities appeared mainly in the adductor longus muscles on slow tau inversion recovery (STIR) images in all the patients without any abnormal signals in the attachment of the ligament, indicating edema changes of the adductor longus muscles which mimiced adductor enthesopathy. Two of the four patients presented with edema changes in the bilateral adductor longus muscles, while the other two were with only unilateral changes. Furthermore, other thigh muscles, including adductor magnus, semitendinosus, sartorius and rectus femoris muscles, could also have mild edema changes in two of the four patients.

Dystrophinopathy can manifest as edema changes in the adductor longus muscles in thigh muscle MRI tests, which is a typical lesion in adductor enthesopathy. The adductor longus muscles in the dystrophinopathy patients may be easy to be impaired due to traction injury during sports.