PiebaldismProto-Oncogene Proteins c-kitMutationGastrointestinal Stromal TumorsReceptor, Platelet-Derived Growth Factor alphaPoint MutationMutation, MissenseDNA Mutational AnalysisGastrointestinal NeoplasmsFrameshift MutationGerm-Line MutationPedigreeReagent Kits, DiagnosticPolymorphism, Single-Stranded ConformationalHeterozygoteExonsPolymerase Chain ReactionBase SequenceMolecular Sequence DataGenes, p53Mutation RateAmino Acid SubstitutionGenotypeGenetic TestingAllelesPhenotypeHomozygoteCodon, NonsenseSequence Analysis, DNAAmino Acid SequenceSequence DeletionGenes, RecessiveMutagenesis, Site-DirectedDNA PrimersCodonMutagenesisGenes, Dominant