You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Disease"].

Please return the output as a JSON object of the format: {"Disease" : ["COVID-19", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Germline mutations in the RB1 gene in patients with hereditary retinoblastoma. We have analyzed the 27 exons and the promoter region of the RB1 gene in familial or sporadic bilateral retinoblastoma by using single-strand conformation polymorphism analysis. For improvement over previous studies, a new set of primers has been designed, which allow for amplification of the coding and splicing sequences only. The positioning of the polymerase chain reaction (PCR) primers was such that the resulting PCR products were of different sizes, which enabled us to analyze two different exons simultaneously and still distinguish between the banding profiles for both (biplex analysis). By using this approach, we were able to identify mutation in 22 new patients, but the overall efficiency of the procedure when we used a single-pass regimen was only 48%. The mutations were small insertions and deletions and point mutations in roughly equal proportions..
{"Disease": ["familial or sporadic bilateral retinoblastoma", "hereditary retinoblastoma"]}