EPG5-Related Vici Syndrome: A Primary Defect of Autophagic Regulation with an Emerging Phenotype Overlapping with Mitochondrial Disorders.

Abstract

Listen

Translate article

Vici syndrome is a rare, under-recognised, relentlessly progressive congenital multisystem disorder characterised by five principal features of callosal agenesis, cataracts, cardiomyopathy, combined immunodeficiency and oculocutaneous hypopigmentation. In addition, three equally consistent features (profound developmental delay, progressive failure to thrive and acquired microcephaly) are highly supportive of the diagnosis. Since its recognition as a distinct entity in 1988, an extended phenotype with sensorineural hearing loss, skeletal myopathy and variable involvement of virtually any organ system, including the lungs, thyroid, liver and kidneys, have been described.Autosomal recessive mutations in EPG5 encoding ectopic P-granules autophagy protein 5 (EPG5), a key autophagy regulator implicated in the formation of autolysosomes, were identified as the genetic cause of Vici syndrome. The eight key features outlined above are highly predictive of EPG5 involvement, with pathogenic EPG5 mutations identified in >90% of cases where six or more of these features are present. The manifestation of all eight features has a specificity of 97% and sensitivity of 89% for EPG5-related Vici syndrome. Nevertheless, substantial clinical overlap exists with other multisystem disorders, in particular congenital disorders of glycosylation and mitochondrial disorders. Clinical and pathological findings suggest Vici syndrome as a paradigm of congenital disorders of autophagy, a novel group of inherited neurometabolic conditions linking neurodevelopment and neurodegeneration due to primary autophagy defects.Here we describe the diagnostic odyssey in a 4-year-old boy whose clinical presentation with multisystem manifestations including skeletal myopathy mimicked a mitochondrial disorder. A genetic diagnosis of Vici syndrome was made through whole genome sequencing which identified compound heterozygous variants in EPG5. We also review the myopathic presentation and morphological characterisation of previously reported cases.