Protein Recommendations

Deletion-insertion Variant


Deletion-insertion (delins)
a sequence change between the translation initiation (start) and termination (stop) codon where, compared to a reference sequence, one or more amino acids are replaced with one or more other amino acids and which is not a substitution, frame shift or conversion.


Format: “prefix”“amino_acid(s)+position(s)_deleted”“delins”“inserted_sequence”, e.g. p.(Arg123_Lys127delinsSerAsp)

“prefix” = reference sequence used = p.
“amino_acid(s)+position(s)_deleted” = position amino acid or range of amino acids deleted = Arg123_Lys127
“delins” = type of change is a deletion-insertion = delins
“inserted_sequence” = description inserted sequence = SerAsp


  • prefix reference sequence accepted is “p.” (protein).
  • by definition, when one amino acid is replaced with one other amino acid, the change is a substitution.
  • for all descriptions the most C-terminal position possible of the reference sequence is arbitrarily assigned to have been changed (3’rule)
  • predicted consequences, i.e. without experimental evidence (no RNA or protein sequence analysed), should be given in parentheses, e.g. p.(Arg123_Lys127delinsSerAsp).
  • when the inserted protein sequence is large and it is possible to derive the inserted amino acid sequence from the description given at DNA or RNA level, the insertion may be described by its length only (e.g. p.Arg456_Leu488delins(54)).
  • two variants separated by one or more amino acids should preferably be described individually and not as a “delins”
  • variants should be described on the protein level and not incorporate knowledge regarding the change at the DNA level.
    • deletion-insertion variants containing a translation stop codon in the inserted DNA sequence are described as insertion, not as a deletion-insertion removing the entire C-terminal amino acid sequence
    • deletion-insertion variants encoding an open reading frame but after the DNA insertion shifting to another reading are described as a frame shift
    • deletion/insertion variants extending the amino acid sequence at the C-terminal end with one or more amino acids are described as Extension.
    • deletion-insertion variants on DNA/RNA level starting starting 5’ of and including the translation termination (stop) codon are described as frame shift.


  • p.Cys28delinsTrpVal
    a deletion of amino acid Cys28, replaced with TrpVal
  • p.Cys28_Lys29delinsTrp
    a deletion of amino acids Cys28 and Ly29, replaced with Trp
  • p.(Pro578_Lys579delinsLeuTer)
    the predicted change at the protein level resulting from DNA variant c.1733_1735delinsTTT is a deletion of amino acids Pro578 and Lys579 replaced with LeuTer
    NOTE: the predicted consequence of variant c.1732_1794del is p.(Pro578_Gln598del). Although the proteins resulting from the changes c.1733_1735delinsTTT and c.1732_1794del are identical, their HGVS description is different. Example derives from the SLC34A3 gene, coding DNA reference sequence NM_080877.2)
  • NP_003070.3:p.(Glu125_Ala132delinsGlyLeuHisArgPheIleValLeu)
    the predicted change at the protein level resulting from DNA variant NM_003079.4:c.374_395inv is a deletion of amino acids Glu125 to Ala132 replaced with GlyLeuHisArgPheIleValLeu. NOTE: the predicticted consequence from the inversion on DNA level is described as a deletion-insertion (inversion descriptions are not used at protein level)
  • p.[Ser44Arg;Trp46Arg]
    the change of two variants affecting amino acids separated by another amino acid.
    NOTE: the variant is not described as p.Ser44_Trp46delinsArgLeuArg


What is an "indel"?

The term "indel" is not used in HGVS nomenclature (see Glossary). The term is confusing, having different meanings in different disciplines.

Can I describe a TrpSer to CysArg variant as a amino acid substitution (p.TrpSer23CysArg)?

No, this is not allowed. By definition a substitution changes one amino acid into one other amino acid. The change TrpSer to CysArg should be described as p.Trp23_Ser24delinsCysArg, i.e. a deletion/insertion (indel) (see Deletion-Insertion).