The entire coding region of the TSC1 gene has been screened for
mutations in 79 unrelated patients
with tuberous sclerosis. Causative mutations have been found in 27 of these
patients and five other
variations in the gene have been identified. 26 of the mutations are predicted
to cause premature
truncation of the protein product of the gene and one mutation is in a
splice site. The mutation screen
has revealed that TSC1 mutations are rarer in sporadic tuberous sclerosis
patients than in familial
cases. We have also found that the only previously described case of non-penetrance
can no longer
be described as such, and that a single ungual fibroma is not necessarily
diagnostic of tuberous
sclerosis, important findings for the genetic counselling of tuberous sclerosis
patients.