Clinical pedigree drawing guidelines: NSGC 1995, 2008 and 2022 standards
Clinical pedigree drawing is governed by a small set of published guidelines, primarily from the NSGC Pedigree Standardization Work Group. This page summarises Bennett et al. 1995, the 2008 update, and the 2022 update, with the related ISCN, HGNC, and HPO references. Each guideline is cited so the source documents can be consulted directly.
Short version. Clinical pedigree drawing follows the NSGC Pedigree Standardization Work Group conventions originally published by Bennett et al. in 1995, updated in 2008, and most recently updated in 2022 to address sex versus gender. ISCN governs broader cytogenomic nomenclature; HGNC governs gene symbols; HPO governs phenotype terms. Each is the canonical reference for its domain.
Bennett et al. 1995: the foundational paper
The original symbol set for clinical pedigree drawing was published by Bennett, Steinhaus, Uhrich, O'Sullivan, Resta, Lochner-Doyle, Markel, Vincent, and Hamanishi in the Journal of Genetic Counseling in 1995: "Recommendations for standardized human pedigree nomenclature" (J Genet Couns. 1995;4(4):267-279, PMID: 11653333). The paper defined the convention set that has formed the backbone of clinical pedigree drawing since: squares and circles for sex; filled symbols for affected individuals; diagonal lines for the deceased; the proband arrow; consanguinity loops; pregnancy outcomes; twins; adoption.
The 2008 update
Bennett, French, Resta, and Doyle published an update in the Journal of Genetic Counseling in 2008: "Standardized human pedigree nomenclature: update and assessment of the recommendations of the National Society of Genetic Counselors" (J Genet Couns. 2008;17(5):424-433, PMID: 18792771, doi:10.1007/s10897-008-9169-9). The 2008 update added clarifications on assisted reproductive technology (ART) annotations, surrogacy and gamete donation, sex chromosome aneuploidy notation, and other extensions that had become routine in clinical practice in the years since 1995.
The 2022 update: sex versus gender
The most recent update was published by Bennett, French, Hsu, and McCown in the Journal of Genetic Counseling in 2022: "An update to standardized human pedigree nomenclature for the inclusion of sex and gender diversity" (J Genet Couns. 2022;31(6):1238-1248, doi:10.1002/jgc4.1571). The 2022 update addressed the long-standing ambiguity in the original square / circle / diamond convention: the symbols had always represented sex assigned at birth in relation to inheritance through the X and Y chromosomes, but they had sometimes been applied (incorrectly) as a statement about gender identity. The 2022 update keeps the structural meaning of the symbols, adds explicit notation for trans and non-binary individuals, and clarifies when separate annotation for sex assigned at birth and gender identity is appropriate. Detail is in our gender-inclusive pedigree drawing page.
ISCN: International System for Human Cytogenomic Nomenclature
ISCN governs the broader nomenclature for cytogenomic findings, including chromosome banding designations, structural rearrangement notation, and copy-number annotation. The current edition is ISCN 2024 (published by Karger), succeeding ISCN 2020 and earlier editions. Pedigree drawing intersects ISCN where chromosomal findings (translocations, marker chromosomes, ring chromosomes, copy-number variants) are annotated alongside the family structure. Detail is in our ISCN pedigree symbols page.
HGNC: HUGO Gene Nomenclature Committee
HGNC (genenames.org) maintains the canonical symbols and names for human genes. Gene-symbol annotations in pedigrees should follow HGNC conventions to ensure interoperability. The HGNC database is publicly searchable and is the appropriate cite for any specific gene name used in a pedigree.
HPO: Human Phenotype Ontology
The Human Phenotype Ontology (hpo.jax.org) provides a standardised vocabulary for phenotypic abnormalities. HPO terms are used for phenotype-aware exchange formats including Phenopackets v2 (GA4GH). Where a clinical pedigree records phenotypic features, those features should map to HPO terms for downstream interoperability. Detail is in our phenopackets and pedigree data page.
UK and other national contexts
The NSGC guidelines are the international reference. Within the UK, the British Society for Genetic Medicine (BSGM), the Association of Genetic Nurses and Counsellors (AGNC), and the UK Cancer Genetics Group (UKCGG) operate within the NSGC convention set; service-level documentation typically references NSGC plus local guidance. Health Education England's family-history resources (referenced in our UK clinicians page) sit alongside the NSGC standards as patient-intake tools.
How Evagene maps to the guidelines
Evagene draws to NSGC 2022 by default, with no option to render non-standard symbols. Gene annotations resolve against HGNC; phenotype annotations resolve against HPO; cytogenomic annotations follow ISCN. The catalogue of conditions and traits maps to ICD-10, OMIM, HPO, HGNC, LOINC, NCBI Gene, ClinVar, RxNorm, BNF, and DrugBank. Outputs are illustrative and intended for research, teaching, and family-history documentation; clinical-grade BOADICEA is computed off-platform at canrisk.org via the CanRisk export bridge.