Mitochondrial encephalomyopathies and West's syndrome: a frequently underdiagnosed association

West's syndrome is known to have symptomatic, cryptogenetic and idiopathic forms. Greater knowledge of the different pathologies and the development of new diagnostic techniques have allowed the list of symptomatic forms to be extended and congenital disorders of the metabolism account for a significant percentage as an aetiopathogenic factor. Yet, although it is known that mitochondrial cytopathies can trigger the development of West's syndrome, few reports exist concerning their association. Our aim in this paper is to report on four cases of West's syndrome in which a mitochondrial cytopathy was shown to be an aetiopathogenic factor. Two females and two males aged between 2 and 10 months, who were suffering from West's syndrome. Biochemical and neuroimaging findings suggested a possible mitochondrial cytopathy, which was later confirmed in the four cases on observing a partial deficiency of some of the complexes of the mitochondrial respiratory chain in muscles; this was found to be simple in the first three (complexes III, I and IV, respectively) and combined in the fourth (complexes I and IV). Infantile spasms should be considered as one of the ways mitochondrial encephalomyopathies manifest themselves. As part of the process of diagnosing West's syndrome, we recommend tests be carried out to determine the levels of lactic and pyruvic acid, carnitine and amino acids in plasma, and possibly in the cerebrospinal fluid, as well as those of amino acids and organic acids in urine. A muscular biopsy must also be carried out in patients who are strongly suspected of having a mitochondrial cytopathy, as well as the corresponding molecular genetic study.