Adenylosuccinate lyase deficiency (MIM 103050, ADSL) is a rare autosomal recessive disease causing severe mental retardation and/or autistic features.1,2 Seizures are often observed (80%),3 varying in age of onset (from newborn to late childhood) and nature (tonic-clonic, “suppression burst” pattern, West syndrome, etc), and are very often resistant to all medication. Around 50% of the children show autistic-like behaviour.4 Microcephaly is rare (1/13 of reported cases). Non-specific anomalies of the brain, such as hypoplasia of the vermis, cerebral atrophy,5 lack of myelination,6 white matter anomalies,7 and lissencephaly4 have often been described. ADSL is a homotetramer involved in two distinct steps of purine synthesis, namely (1) the conversion of succinylaminoimidazole carboxamide ribotide (SAICAR) into aminoimidazole carboxamide ribotide (AICAR), and (2) the conversion of adenylosuccinate (S-AMP) into adenosine monophosphate (AMP) in the inosine monophosphate transformation pathway (fig 1). The diagnosis of ADSL deficiency is based on the detection of dephosphorylated SAICAR and S-AMP products, that is, S-Ado (succinyladenosine) and SAICAr (succinylaminoimidazole carboxamide riboside). The modified Bratton-Marshall test is the most …
