SKELETAL-MUSCLE OF PATIENTS WITH GYRATE ATROPHY OF THE CHOROID AND RETINA AND HYPERORNITHINEMIA IN ULTRALOW-FIELD MAGNETIC-RESONANCE-IMAGING AND COMPUTED-TOMOGRAPHY

Gyrate atrophy of the choroid and retina with hyperornithinaemia (GA), an autosomal recessive disease, affects skeletal muscle in addition t o the eye. Muscle biopsy samples show prominent type 2 muscle fibre at rophy. Atrophic fibres also contain accumulations of tubular aggregate s in electron microscopy. To evaluate skeletal muscle involvement in d etail, the thigh muscles of 7 patients with GA were examined using sem i-open conchotome muscle biopsies, computed tomography (CT) and ultral ow-field magnetic resonance imaging (MRI) at 0.02 T. In MRI, the T1 an d T2 proton relaxation times were measured. Type 2 muscle fibre atroph y was found in all biopsy samples (100%) and tubular aggregates in 6 o f the 7 samples studied (87%). The CT density of the muscle tissue was increased in the only child of the study, decreased in 3 elderly subj ects, and normal in the remaining 3 patients. Mean T1 relaxation times of the patients were decreased (135 +/- 5 ms) as compared to those of 6 healthy controls (157 +/- 12 ms) (p = 0.002). The T2 relaxation tim e was slightly increased (40 +/- 3 ms) as compared to the controls (35 +/- 7 ms; not significant, p = 0.3). Our findings suggest that the th igh muscles of the patients with GA universally show changes in CT and MRI studies, but relaxation time measurements gave little additional information on the muscle metabolism.