Retinoblastoma (RB, OMIM#180200) is the most common intraocular tumour in infancy and early childhood. Constituent mutations in the RB1 gene predispose individuals to RB development. We performed a mutational screening of the RB1 gene in Italian patients affected by RB referred to the Medical Genetics of the University of Siena. In 35 unrelated patients, we identified germline RB1 mutations in 6 out of 9 familial cases (66%) and in 7 out of 26 with no family history of RB (27%). Using the single-strand conformational polymorphism (SSCP) technique, 11 novel mutations were detected, including 3 nonsense, 5 frameshift and 4 splicesite mutations. Only two of these mutations (1 splice site and 1 missense) were previously reported. The mutation spectrum reflects the published literature, encompassing predominately nonsense or frameshift and splicing mutations. RB1 germline mutation was detected in 37% of our cases. Gross rearrangements outside the investigated region, altered DNA methylation, or mutations in non-coding regions, may be the cause of disease in the remainder of the patients. Some cases, e.g. a case of incomplete penetrance, or variable expressivity ranging from retinoma to multiple tumours, are discussed in detail. In addition, a case of pre-conception genetic counselling resolved by rescue of banked cordonal blood of the affected deceased child is described.

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The most interesting sources of information about the pathogenesis of posterior capsular opacification seem to be histopathological studies and in vitro tissue cultures. Since our surgical technique is extracapsular cataract extraction, the explants we used for tissue culture consisted of the anterior capsule epithelial sheet without the equatorial germinative zone. We successfully overcame several problems by using the autologous plasma clot culture method. This medium, considered the optimal one for this type of culture, allowed us to study the heterogeneous behavior of the epithelial cells in culture. Using the plasma clot culture method, we were able to demonstrate in vitro fibroblastic transformation of the epithelial cells. Histopathological findings of particular cases of posterior capsule opacification and immunohistochemistry of the human lens are also reported.

Conclusions Type II tyrosinaemia in Italy has no regional preponderance. Neuromotor retardation and/or microcephaly seem to be correlated with the higher values of tyrosine. Enzyme studies have been refused in all patients. Treatment with a low tyrosine diet has been successful when accepted: since in many patients the diagnosis was made rather late, it is not possible to evaluate the results of the diet for the prevention of neuromotor retardation.

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