Different mutations in the same genetic locus causing similar or identical phenotype is?

Allelic heterogeneity Different mutations in the same genetic locus can cause an identical or similar phenotype. eg- different mutations of the b-globin locus- b-thalassemia Phenotypic Heterogeneity When more than one phenotype is caused by allelic mutations e.g. Identical mutations in the FGFR2 gene- Crouzon syndrome or Pfeiffer syndrome Locus or Non-allelic Heterogeneity Similar disease phenotype results from mutations at different genetic loci. eg- osteogenesis imperfecta- mutations in COL1A1 or COL 1A2: located on different chromosomes