A THREE YEAR FOLLOW UP MUSCLE SONOGRAPHIC STUDY IN HIBM PATIENTS

Background: HIBM is a neuromuscular disorder caused by mutation of GNE, UDP-N-acetylglucosamin 2 epimerase/N-acetylmannosamine kinase, on chromosome 9p12-13. Clinically it is characterized by severe progressive muscle weakness affecting distal and proximal limbs,it's onset is in early adulthood. The most prominent type of HIBM is the autosomal recessive form of Persian Jews type II. Histologically rimmed vacuoles with filamentous inclusions are noted in muscle. It is also known as the Quadriceps Sparing Myopathy because of this unusual and unique clinical feature. However a recent publication (Eisenberg et al, 2003) and our own experience indicate that the quadriceps musculature is affected.Objectives: To evaluate the morphological changes of muscle with sonography in a three year follow up study in four patients affected by Hereditary Inclusion Body Myopathy (HIBM).Methods: We studied 4 Persian Jews diagnosed with HIBM type II by muscle biopsy findings and genomic analysis, there were all homozygous for GNE-M712T. Atrophy was determined by echogenicity patterns on gray scale sonography. Sonography of quadriceps and hamstrings muscle groups were initially studied and in our follow up examination we extended our study to their distal anterior and posterior lower limb compartments.Results: A peculiar and newly described finding of central atrophy and peripheral sparing resulting in a target lesion appearance was noticed in the hamstrings compartment of all 4 patients. The quadriceps compartment also showed the target lesion in the rectus femoris, atrophy in the vastus medialis and intermedius muscle of the two with longest disease duration. The severity of atrophy and number of target lesions increased with disease duration. In their follow up examination, three years later, the rectus femoris developed perifascicular and interfascicular edema with a marbled appearance, the vastus medialis, lateralis and intermedius were severly affected by atrophy in the patients with longest disease duration. The rectus femoris and vastus intermedius showed target lesions and marked diffuse atrophy in the patient with shortest disease duration. The hamstring muscles of all again were affected by central atrophy and peripheral sparing. The anterior tibial muscle showed the marbled lesion, the peroneal musculature demonstrated both target and marbled lesion in the patient affected longest. The anterolateral compartment of the leg showed profound atrophy in the rest of the study group. The gastrocnemius muscles were affected by diffuse atrophy in all patients studied.Conclusion: Our study demonstrates that sonography is a helpful non-invasive procedure that can indicate the stage and progression of HIBM disease. The newly described myopathic target lesion may provide a useful adjunct to disease diagnosis. The involvement of the quadriceps compartment has not been previously recognized, this study represents the first use of imaging in HIBM type II patients.1. Eisenberg et al, Mutation Spectrum of GNE in hereditary inclusion myopathy sparing the quadriceps, volume 21, issue 1, 2003Citation: , volume , supplement , year 2003, page Session: Myopathies and soft tissue diseases