FANCB
Chr XXLRFA complementation group B
Also known as: FA2, FAAP90, FAAP95, FAB, FACB
This gene encodes a DNA repair protein required for FANCD2 ubiquitination and is assembled into a nucleoprotein complex that repairs DNA lesions. Mutations cause Fanconi anemia complementation group B and can also cause VACTERL syndrome with hydrocephalus. The gene follows X-linked recessive inheritance and is highly constrained against loss-of-function variants.
Definitive — sufficient evidence for diagnostic panels
Population Genetics & Constraint
gnomAD v4 — loss-of-function & missense intolerance
Highly LoF-intolerant (top ~10% of genes)
Tolerant to missense variation
The highest-scoring mechanism for this gene is loss-of-function (haploinsufficiency).
Predictions from Badonyi M, Marsh JA. PLoS ONE. 2024;19(8):e0307312. Mechanism ranking also informed by gnomAD constraint, ClinVar, and ClinGen data.
ClinVar Variant Classifications
400 submitted variants in ClinVar
Classification Summary
Curated Variants Distribution
Classified variants from ClinVar · 5 ACMG categories
| Classification | LoF | Missense + Inframe | Non-coding | Synonymous | Total |
|---|---|---|---|---|---|
Pathogenic | 3 | 1 | 17 | 0 | 21 |
Likely Pathogenic | 4 | 2 | 0 | 0 | 6 |
VUS | 3 | 161 | 10 | 3 | 177 |
Likely Benign | 0 | 14 | 46 | 99 | 159 |
Benign | 0 | 0 | 13 | 11 | 24 |
Conflicting | — | 13 | |||
| Total | 10 | 178 | 86 | 113 | 400 |
LoF = frameshift, stop gained/lost, canonical splice · Counts from ClinVar esearch · Updated hourly
View in ClinVar →Protein Context — Lollipop Plot
FANCB · protein map & ClinVar variants
Showing all ClinVar variants across the protein. Search a specific variant to highlight its position.
3D Protein StructureAlphaFold
External Resources
Links to major genomics databases and tools
Clinical Trials
Active and recruiting trials from ClinicalTrials.gov
External Resources
Links to major genomics databases and tools