D.P.17 Whole body muscle MRI in three patients suffering from XMEA: A peculiar involvement pattern

Abstract

X-linked myopathy with excessive autophagy (XMEA) is a rare childhood-onset disease characterized by progressive vacuolation and atrophy of skeletal muscle. It is caused by mutations in the VMA21 gene. The VMA21 protein is an essential assembly chaperone of the V-ATPase, the principal mammalian proton pump complex. Decreased VMA21 is thought to raise lysosomal pH, which reduces lysosomal degradative ability and blocks autophagy. In patients with inherited muscular disorders, extensive evaluation of muscle alterations by magnetic resonance imaging (MRI) can significantly contribute to a specific diagnosis. The aim of this work was to describe muscle involvement on whole-body MRI scans in three patients from two separate families, presenting with XMEA confirmed by genetic testing. Patients 1, 2 and 3 were aged of 13, 41 and 30 respectively. Patients 1 and 2 were related. Patients 1 and 3 were ambulatory, presenting with lower limb girdle myopathy and mainly proximal amyotrophy. Patient 2 was in electrical wheel chair with movements basically restricted to the hands. In the three patients, whole-body imaging was performed on a 1.5-tesla MRI system. Selected imaging sequences were T1-weighted turbo spin echo and STIR (short T1 inversion recovery) with axial slices and coronal reconstruction. No paramagnetic contrast agent was injected. Muscles changes consisted essentially of fat replacement with faded signal. In patients 1 and 3, most affected muscles were vastus lateralis, vastus medialis, soleus, adductor magnus, gluteus maximus. Rectus femoris was relatively spared. In patient 1 (youngest one), upper limb and girdle muscles were normal. In patient 2, shoulder muscles and biceps brachialis were affected. In patient 3, all muscle territories but the anterior compartment of the leg and the forearms were involved. Description of MRI patterns of muscle involvement can therefore help providing diagnosis clues when XMEA is suspected.