Unusually mild tuberous sclerosis phenotype is associated with TSC2 R905Q mutation.

OBJECTIVE: To report the clinical manifestations and functional aspects of Tuberous Sclerosis Complex (TSC), resulting from Codon 905 mutations in TSC2 gene. METHODS: We performed a detailed study of the TSC phenotype and genotype in a large French-Canadian kindred (Family A). Subsequently, clinical and molecular data on 18 additional TSC families with missense mutations at the same codon of TSC2 were collected. Functional studies were performed on the different missense changes and related to the phenotype. RESULTS: A 2714G>A (R905Q) mutation was identified in Family A. The TSC phenotype in this family was unusually mild and characterized by hypomelanotic macules or focal seizures that remitted spontaneously or were easily controlled with medication. Diagnostic criteria were met in only a minority of mutation carriers. Other families with the R905Q mutation were found to have a similar mild phenotype. In contrast, patients with a 2713C>T (R905W) or a 2713C>G (R905G) mutation had more severe phenotypes. Although all three amino acid substitutions were pathogenic, the R905W and R905G substitutions affected tuberin function more severely than R905Q. INTERPRETATION: Codon 905 missense mutations in TSC2 are relatively common. The TSC2 R905Q mutation is associated with unusually mild disease, consistent with functional studies. Combined with previous reports, it is apparent that certain TSC2 missense mutations are associated with a mild form of tuberous sclerosis, which in many patients does not meet standard diagnostic criteria. These findings have implications for the large number of patients with limited clinical features of TSC and for genetic counseling in these families.

Transient edematous lesions of the splenium in epileptic patients.

BACKGROUND: Transient focal lesions in the splenium of the corpus callosum (SCC) have been previously described in patients with epilepsy or without epilepsy but receiving antiepileptic drugs (AED). CASE REPORTS: Two epileptic patients were admitted to our long-term monitoring unit. Antiepileptic drugs were completely discontinued a few days later. One patient had no seizures. The other had three attacks, the last of which occurred two days before a brain magnetic resonance imaging (MRI) was performed. In both cases brain MRI showed a lesion in the SCC characterized by high signal on T2-weighted images and no enhancement after Gadolinium infusion. The patients were discharged with their pre-admission medications. A follow-up MRI five weeks later showed resolution of the SCC lesions. CONCLUSIONS: The pathogenesis of transient SCC lesions in epileptic patients is still unclear. In our patients, either the sudden AED withdrawal or the seizures activity may be presumed to be the cause, though an individual susceptibility must also be considered.