Description MLPA deletion

Chiara Maragno

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Nov 17, 2025, 5:24:53 AMNov 17

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Dear HGVS support,

I have a question about the description in case of deletion. I found with MLPA analysis a deletion from Exon 1 to Exon 6 of CFHR3 gene and from exon 1 to exon 6 of CFHR1 gene in heterozygous.

In the section "Reccomandation-DNA-deletion" i have read the exampe about deletion of DMD gene.

So, it is correct to write this way: NC_000001.10:g.(196725407_196737914)_(196801143 _196857047)del ?

Could you also tell me how to specify that the deletion is in heterozygous? I haven't found any examples.

Thanks for your help.

--

Dott.ssa Chiara Maragno.
UOC Laboratorio Analisi-UOS Laboratorio Genetica Medica
Pad. Invernizzi-Fondaz. IRCCS Ca' Granda Ospedale Maggiore Policlinico -
via F. Sforza, 35 - 20122 Milano
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Johan den Dunnen

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Nov 19, 2025, 8:17:57 AMNov 19

to HGVS Nomenclature

Dear Chiara,

the description NC_000001.10:g.(196725407_196737914)_(196801143 _196857047)del follows current HGVS nomenclature recommendations. It indicates you detected a deletion on chr1 which, based on the hg38 reference sequence, extends from minimally position g.196737914 to g.196801143 and maximally from position g.196725407 to g.196857047. Since you give a description for one allele only, it automatically indicates the variant was detected in heterozygous state. When you want to indicate the other allele is not affected, you can use the format explained on the Alleles page (see https://hgvs-nomenclature.org/stable/recommendations/DNA/alleles/).

Best regards,

Johan den Dunnen
HUGO HGVS Variant Nomenclature Committee (HVNC)

Op maandag 17 november 2025 om 11:24:53 UTC+1 schreef Chiara Maragno:

Chiara Maragno

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Nov 20, 2025, 10:32:03 AMNov 20

to HGVS Nomenclature

Dear HGVS support,

sorry but i forgot to indicate that the reference genome is hg37.

So, if the deletion is in homozygous is correct write: NC_000001.10:g.[(196725407_196737914)_(196801143 _196857047)del] ; [(196725407_196737914)_(196801143 _196857047)del] ?

And, if is in heterozygous: NC_000001.10:g.[(196725407_196737914)_(196801143 _196857047)del] ; [=] ?

Best regards

Chiara Maragno

Johan den Dunnen

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Nov 21, 2025, 8:50:04 AMNov 21

to HGVS Nomenclature

Dear Chiara,

> sorry but I forgot to indicate that the reference genome is hg37

NC_000001.10 is hg19 reference sequence, so this is indicated "automatically".

The descriptions you give for homozygous and heterozygous descriptions are correct, i.e. HGVS nomenclature does not use spaces so it should be "];[" and not "] ; [".