Pedigree
Multi-generation genetic inheritance charts for clinical genetics. Affected/carrier/presymptomatic status fills, proband arrow markers, consanguinity. Standardized human pedigree nomenclature.
pedigree·§ ISCN / Bennett
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Genetics pedigree chart standard — tracking the inheritance pattern of a specific trait or disease within a family.
References:
- Bennett, R.L. et al. (1995). Recommendations for standardized human pedigree nomenclature. Am J Hum Genet, 56(3), 745-752.
- Bennett, R.L. et al. (2008). Standardized human pedigree nomenclature: Update and assessment. J Genet Couns, 17(5), 424-433.
- Bennett, R.L. (2022). The evolving pedigree: Updating to reflect modern family structures, sex, and gender. J Genet Couns, 31(6), 1267-1275. ← Latest standard
- NSGC (National Society of Genetic Counselors) pedigree standardization committee
1. Key Differences from Genogram
| Aspect | Genogram | Pedigree Chart |
|---|---|---|
| Primary use | Family relationships + medical + psychological + social work assessment | Pure genetic tracking (single or few traits) |
| Condition representation | Multiple condition fill patterns (22 categories) | Only affected/carrier/unaffected (1–3 traits) |
| Relationship quality | Yes (34 types of emotional relationships) | No (mated/not mated only) |
| Generation labels | None | Roman numerals (I, II, III...) |
| Individual labels | Name + birth year | Generation-number (II-3) + optional name |
| Proband | None (has Index Person) | Yes (arrow pointing to index case, P marker) |
| Consultand | None | Yes (arrow + C marker) |
| Consanguinity | Optional annotation | Critical information (double line, must be shown) |
| Sex vs Gender | Traditional binary | Bennett 2022: sex ≠ gender; diamond for unknown/DSD |
| Relationship representation | Detailed (divorce, separation, cohabitation) | Simplified (mated line, no longer together, consanguinity) |
2. Individual Symbols
2.1 Core Shapes (Bennett 2022 Updated)
| Symbol | Shape | Meaning | DSL |
|---|---|---|---|
| □ | Square | AMAB (Assigned Male at Birth) | [male] or [amab] |
| ○ | Circle | AFAB (Assigned Female at Birth) | [female] or [afab] |
| ◇ | Diamond | UAAB (Unknown/Ambiguous at Birth) / DSD / Non-disclosed | [unknown] or [uaab] |
Important Bennett 2022 updates:
- Square/Circle now formally represent assigned sex at birth, not gender identity
- Diamond is used for: sex unknown, differences of sex development (DSD/intersex), non-disclosed, or still in utero (sex unknown)
- If gender identity differs from assigned sex, annotate with a label (do not change the shape)
- Example: transgender woman (AMAB) → square shape + "TW" label or gender annotation
2.2 Affected Status
| Status | Fill Pattern | SVG | DSL |
|---|---|---|---|
| Unaffected | Empty (white fill) | fill: white | (default) |
| Affected (single trait) | Full fill (black/dark) | fill: #333 | [affected] |
| Carrier (autosomal) | Half-filled (left half, vertical divide) | <clipPath> left half | [carrier] |
| Carrier (X-linked female) | Dot in center | Small <circle> inside | [carrier-x] |
| Obligate carrier | Dot in center | Small filled <circle> inside | [obligate-carrier] |
| Asymptomatic/presymptomatic | Vertical line through shape | <line> through center | [presymptomatic] |
| Multiple traits | Quadrant fill (like genogram) | See below | [affected: trait1 + trait2] |
Multi-trait pedigree (up to 4 traits):
# Legend defines what each quadrant means
pedigree "Breast/Ovarian Cancer Family"
legend: trait1 = "Breast cancer" (fill: quad-tl)
legend: trait2 = "Ovarian cancer" (fill: quad-tr)
legend: trait3 = "Prostate cancer" (fill: quad-bl)
I-1 [male, affected: trait3] # bottom-left quadrant filled
I-2 [female, affected: trait1] # top-left quadrant filled
II-3 [female, affected: trait1+trait2] # top-left + top-right filled2.3 Life Status Symbols
| Status | Visual | SVG | DSL |
|---|---|---|---|
| Alive | Normal shape | Default rendering | (default) |
| Deceased | Diagonal slash through shape (/) | Single <line> top-right to bottom-left | [deceased] |
| Stillborn (SB) | Small shape + SB text | 60% scale + label "SB" | [stillborn] |
| Pregnancy (P) | Diamond (sex unknown) or shape with P | shape + "P" label | [pregnancy] |
| Spontaneous abortion (SAB) | Small triangle | <polygon> 15×15 | [sab] |
| Induced abortion (TAB) | Small triangle with horizontal line | <polygon> + <line> | [tab] |
| Ectopic pregnancy (ECT) | Small triangle + ECT label | <polygon> + text | [ectopic] |
| Affected SAB | Filled small triangle | <polygon> filled | [sab, affected] |
Bennett 2022 Note:
- The deceased marker was updated from the traditional "X through shape" to "diagonal slash (/)", which differs from the X marker used in genograms
- This is an important visual distinction between pedigrees and genograms
2.4 Special Markers
| Marker | Symbol | Position | DSL |
|---|---|---|---|
| Proband | Arrow (↗) pointing to shape + "P" | Lower-left | [proband] |
| Consultand | Arrow (↗) pointing to shape + "C" | Lower-left | [consultand] |
| Evaluated | "E" above or inside shape | Above | [evaluated] |
| No offspring by choice | Crossed out drop line | Below couple line | [no-children] |
| Infertility | Crossed out drop line + "∞" | Below couple line | [infertile] |
| Adopted in | Brackets around shape | [ shape ] | [adopted-in] |
| Adopted out | Brackets around shape, dashed line to parents | [ shape ] + dashed line | [adopted-out] |
2.5 Assisted Reproduction (Bennett 2022)
Bennett 2022 added standard symbols for assisted reproduction, which are increasingly important in modern clinical practice:
| Type | Symbol | DSL |
|---|---|---|
| Donor egg | "D" on connecting line from egg donor | [donor-egg] |
| Donor sperm | "D" on connecting line from sperm donor | [donor-sperm] |
| Donor embryo | "D" on connecting lines from both donors | [donor-embryo] |
| Surrogacy (gestational) | "S" label on surrogate, dashed line to child | [surrogate] |
| IVF | "IVF" label on couple line | annotated on couple line |
3. Relationship Lines (Pedigree-Specific)
Pedigree relationship lines are much simpler than those in genograms — there are no emotional relationships, only structurally relevant genetic lines.
3.1 Partnership Lines
| Type | Line Style | DSL | Meaning |
|---|---|---|---|
| Mated (together) | Single horizontal solid line | A -- B | Partners with offspring |
| Mated (no longer together) | Single line + single slash | A -/- B | Separated (divorce/separation not distinguished) |
| Consanguinity | Double horizontal line | A == B | Consanguineous union (genetically critical!) |
| Relationship line (no offspring) | Single horizontal dashed | A ~ B | Partners with no offspring |
3.2 Parent-Child Lines
| Type | Line | DSL |
|---|---|---|
| Biological | Solid vertical | (default) |
| Adopted in | Dashed vertical + brackets on child | [adopted-in] |
| Adopted out | Dashed vertical + brackets, line goes to new parents | [adopted-out] |
| Identical twins | V-shape (meet at single point) | [twin-mz] (monozygotic) |
| Fraternal twins | Inverted-V with horizontal bar | [twin-dz] (dizygotic) |
| Twins (unknown zygosity) | Inverted-V, question mark on bar | [twin-unknown] |
| Triplets+ | 3+ lines from point/bar | [triplet-mz] etc. |
4. Generation and Individual Labeling
4.1 Generation Labels
- Roman numerals (I, II, III, IV...) are displayed on the left side
- I = the oldest generation
- Aligned to the center Y-coordinate of that generation
- Font: bold, 14px, class="schematex-generation-label"
4.2 Individual Labels
- Numbered left to right within each generation: 1, 2, 3...
- Full identifier:
II-3= the 3rd individual in the second generation - Displayed below the shape
- Proband and consultand have an additional arrow marker
4.3 Legend (Required for Multi-Trait Pedigrees)
- Pedigree diagrams must include a legend explaining the fill pattern meanings
- The legend is typically placed in the bottom-right corner or at the bottom of the chart
- Legend content: the fill pattern + color corresponding to each trait
5. Layout Rules
Shares most layout logic with genogram (generation alignment, male-left, children ordering), with the following differences:
5.1 Pedigree-Specific Layout
- Generation label column: Reserve a 40px column on the left for Roman numerals
- Individual numbering: Display "II-3" format identifiers below each shape
- No emotional lines: Emotional relationship routing is not needed
- Consanguinity emphasis: Double lines must be clearly visible, as this is critical genetic information
- Proband arrow: Points at 45° from lower-left to the proband shape, length 20px
- Legend box: Bottom-right or bottom of diagram, containing trait descriptions
5.2 Spacing (Pedigree-Specific Adjustments)
| Parameter | Default | Difference from Genogram |
|---|---|---|
| Left margin (for gen labels) | 50px | Genogram has no such requirement |
| Node width | 40px | Same |
| Node height | 40px | Same |
| Generation spacing | 100px | Slightly less than genogram (120px), because there are no emotional lines |
| Sibling spacing | 50px | Slightly less than genogram (60px) |
| Legend box width | 150px | Genogram has no such requirement |
| Legend box height | auto (based on traits) | — |
6. DSL Grammar (Pedigree — Expanded)
document = header legend_def* statement*
header = "pedigree" quoted_string? NEWLINE
legend_def = "legend:" IDENTIFIER "=" quoted_string legend_fill? NEWLINE
legend_fill = "(" "fill:" FILL_SPEC ")"
FILL_SPEC = "full" | "quad-tl" | "quad-tr" | "quad-bl" | "quad-br"
| "half-left" | "half-right" | "striped" | "dotted"
statement = comment | individual_def | couple_def
individual_def = ID properties? NEWLINE
properties = "[" property ("," property)* "]"
property = sex_prop | status_prop | genetic_prop | special_prop | kv_prop
sex_prop = "male" | "female" | "unknown" | "amab" | "afab" | "uaab"
status_prop = "deceased" | "stillborn" | "pregnancy"
| "sab" | "tab" | "ectopic"
genetic_prop = "affected" | "carrier" | "carrier-x" | "obligate-carrier"
| "presymptomatic" | "unaffected"
| "affected:" trait_list
trait_list = IDENTIFIER ("+" IDENTIFIER)*
special_prop = "proband" | "consultand" | "evaluated"
| "adopted-in" | "adopted-out"
| "donor-egg" | "donor-sperm" | "donor-embryo" | "surrogate"
| "no-children" | "infertile"
| "twin-mz" | "twin-dz" | "twin-unknown"
| "triplet-mz" | "triplet-dz"
couple_def = ID couple_op ID couple_label? NEWLINE (INDENT child+ DEDENT)?
couple_op = "--" | "==" | "-/-" | "~"
couple_label = "[" kv_prop "]"
child = individual_def
comment = "#" [^\n]* NEWLINE
ID = /[a-zA-Z][a-zA-Z0-9_-]*/
IDENTIFIER = /[a-zA-Z][a-zA-Z0-9_-]*/
VALUE = /[^\],\n]+/
quoted_string = '"' /[^"]*/ '"'
INDENT = increase in leading whitespace (2+ spaces)
DEDENT = decrease in leading whitespace
NEWLINE = /\n/7. Test Cases
Case 1: Autosomal Recessive (Cystic Fibrosis)
pedigree "Cystic Fibrosis Family"
I-1 [male, carrier]
I-2 [female, carrier]
I-1 -- I-2
II-1 [male, unaffected]
II-2 [female, carrier]
II-3 [male, affected, proband]
II-4 [female, unaffected]Verify: I-1/I-2 are half-filled (carrier), II-3 is full-filled + proband arrow, "I" and "II" labels appear on the left.
Case 2: Consanguinity
pedigree "Consanguineous Marriage"
I-1 [male, carrier]
I-2 [female, unaffected]
I-1 -- I-2
II-1 [male, carrier]
II-2 [female, unaffected]
I-3 [male, unaffected]
I-4 [female, carrier]
I-3 -- I-4
II-3 [female, carrier]
II-1 == II-3
III-1 [male, affected, proband]Verify: The line between II-1 and II-3 is double (consanguinity), III-1 is full-filled + proband arrow.
Case 3: X-Linked Recessive (Hemophilia)
pedigree "Hemophilia A"
I-1 [male, unaffected]
I-2 [female, carrier-x]
I-1 -- I-2
II-1 [male, affected]
II-2 [female, carrier-x]
II-3 [male, unaffected]
II-4 [female, unaffected]
II-2 -- II-5 [male, unaffected]
III-1 [male, affected]
III-2 [female, carrier-x]
III-3 [male, unaffected]Verify: carrier-x females have a center dot, affected males are full-filled.
Case 4: Multi-Trait Pedigree
pedigree "Cancer Family Syndrome"
legend: breast = "Breast cancer" (fill: quad-tl)
legend: ovarian = "Ovarian cancer" (fill: quad-tr)
legend: prostate = "Prostate cancer" (fill: quad-bl)
legend: colon = "Colon cancer" (fill: quad-br)
I-1 [male, affected: prostate, deceased]
I-2 [female, affected: breast, deceased]
I-1 -- I-2
II-1 [female, affected: breast+ovarian]
II-2 [male, unaffected]
II-3 [female, unaffected, evaluated]
II-1 -- II-4 [male, unaffected]
III-1 [female, unaffected, proband]
III-2 [male, unaffected]Verify: legend box shows the 4 trait quadrant fills, I-1 has quad-bl filled, II-1 has quad-tl + quad-tr filled, III-1 has proband arrow.
Case 5: Modern Family (Bennett 2022 — Assisted Reproduction)
pedigree "Donor Conception"
I-1 [male]
I-2 [female]
I-1 -- I-2
II-1 [female]
donor [male, donor-sperm]
II-1 -- II-2 [male]
III-1 [female, proband]Verify: donor-sperm annotation appears on the connecting line from donor to child, donor node display is optional.
Case 6: Pregnancy / Loss
pedigree "Reproductive History"
I-1 [male]
I-2 [female]
I-1 -- I-2
II-1 [male]
II-2 [female, sab]
II-3 [male, stillborn]
II-4 [female, pregnancy]
II-5 [female]Verify: II-2 is a small triangle (SAB), II-3 is a small shape + SB label + deceased slash, II-4 is a diamond/shape with "P".
Case 7: Large Pedigree (5 Generations)
pedigree "Huntington Disease"
I-1 [male, affected, deceased]
I-2 [female, deceased]
I-1 -- I-2
II-1 [male, affected, deceased]
II-2 [female, unaffected]
II-3 [male, unaffected, deceased]
II-1 -- II-4 [female, unaffected]
III-1 [female, affected]
III-2 [male, presymptomatic]
III-3 [female, unaffected]
III-1 -- III-4 [male, unaffected]
IV-1 [male, presymptomatic, proband]
IV-2 [female, unaffected]
III-3 -- III-5 [male, unaffected]
IV-3 [male, unaffected]
IV-4 [female, unaffected]
IV-1 -- IV-5 [female, unaffected]
V-1 [unknown, pregnancy]Verify: 5-generation Roman numeral labels (I–V), presymptomatic individuals have a vertical line marker, V-1 is a pregnancy diamond.
8. Implementation Priority
| Priority | Feature | Complexity |
|---|---|---|
| P0 (Phase 2.1) | Basic pedigree layout reusing genogram engine + Roman numeral labels + individual numbering | Medium |
| P0 | Affected/carrier/unaffected fill + proband arrow | Low |
| P1 | Consanguinity double line (already in genogram, but critical for pedigree) | Low |
| P1 | Deceased slash (/ not X), SAB/TAB/stillborn symbols | Medium |
| P1 | Legend box rendering | Medium |
| P2 | Multi-trait quadrant fill system | Medium |
| P2 | X-linked carrier dot | Low |
| P2 | Bennett 2022 sex/gender annotation | Low |
| P2 | Assisted reproduction symbols (donor, surrogate) | Medium |
| P3 | Presymptomatic vertical line marker | Low |
| P3 | Adopted in/out bracket notation | Low |
Ecomap
Family systems embedded in institutional, social, and cultural support networks. Radial layout with weighted connection strengths and directional energy flow arrows. Based on Hartman (1978).
Phylogenetic tree
Evolutionary trees with Newick/NHX input, clade coloring, bootstrap support values, proportional branch lengths. Indent-based DSL alternative also supported.