Muscle-eye-brain disease. Santavuori syndrome.
Incidence
The syndrome is familial and is transmitted as an autosomal recessive trait. Originally, most patients came from a geographically isolated area in Finland. In later studies, the syndrome was reported in other areas.
Clinical Characteristics
Muscle-eye-brain disease is characterized by eye involvement (congenital myopia and glaucoma, retinal hypoplasia), mental retardation, and structural brain involvement (pachygyria, flat brainstem, and cerebellar hypoplasia with cerebellar cysts). The brain involvement is less severe compared to what is found in Walker-Warburg syndrome. Typically, muscle-eye-brain disease patients present in the neonatal period with hypotonia and poor visual alertness. Patients at the severe end of the spectrum remain bedridden, never achieve sitting, head control, or visual contact. These patients may die during the first years of life. Moderately affected patients usually show high myopia but have some preserved vision, enabling them to establish contact. Their maximum motor ability is to sit unsupported and, occasionally, to speak a few words. Patients at the milder end of the spectrum may acquire ambulation for a number of years. Often their functional abilities are more impaired by the coexistence of spasticity than weakness. Vision is preserved in these patients, and limited verbal communication skills are possible. Epilepsy is a common complication of muscle-eye-brain disease. It is due to defects of glycosyltransferases (dystroglycanopathies).
Precipitants
The usual precautions that should be observed for all patients with a muscular dystrophy and elevated serum CK should be followed.
Provocation Tests
None
Diagnostic Procedures
Brain MRI and ophthalmological examination will help to recognize the typical associated features. Serum CK levels are typically elevated (more than 10 times normal values). The muscle biopsy will show reduced or absent alpha-dystroglycan using antibodies that recognize a glycosylated epitope. Mutation analysis of the O-mannose beta-1,2-N-acetylglucosaminyltransferase gene will confirm the diagnosis.