Abstract
Purpose::
to study phenotype-genotype correlation in 65 consecutive patients with retinoblastoma seen between March 2004 and January 2006 and to report undescribed Rb1 mutations identified in patients seen earlier.
Methods::
Complete ophthalmic examination was performed in all patients and their parents. DNA was extracted from peripheral blood leucocytes and the Rb1 gene was screened by DHPLC and direct sequencing of the promoter and all the exons.
Results::
Thirty-two patients had bilateral retinoblastoma while thirty-three had unilateral retinoblastoma. Overall, 29 mutations were found in 65 patients (45 %). However, mutations were detected in 78% of the patients with bilateral retinoblastoma (25 out of 32 patients) and only in 12% of the patients with unilateral retinoblastoma (4 out of 33 patients). Twenty-two mutations were single-base substitutions (76 %). Of these mutations 68% were of the nonsense type (15 cases).Ten patients with bilateral retinoblastoma in whom mutations were detected in a non-systematic approach between 1995 and 1998 were added to our recent series. In total, ten novel mutations were identified, including 4 single base substitutions, 4 small deletions and 2 small duplications. These are g.39445G>A, g.41924A>G, g.56851A>G, g.156795T>G, g.41983delT, g.44699_44706delAGCAGTTC, g.73788_73789delAA, g.78253delA, g.2157dupC and g.2179_2183dupGGACC. Two patients had dysmorphic features associated with 13q14 large deletions.
Conclusions::
Low penetrance was observed in patients with the R661W mutations. All other mutations were associated with complete penetrance. As already reported, large deletions may be associated with a more severe syndromic form of retinoblastoma.
Keywords: retinoblastoma • mutations • gene screening