| Domain | Best-supported finding | Quantitative evidence | Evidence type/source |
|---|---|---|---|
| Disease identifiers | ABL1-related congenital heart defects and skeletal malformations syndrome is a Mendelian developmental disorder linked to **MONDO:0060532** and **ABL1**; Open Targets shows a single strong disease-target association for ABL1. | Open Targets association score **0.8012**; evidence count **5** tied to the foundational literature. | Curated disease-target resource and literature linkage (Open Targets context) (pqac-00000000) |
| Core definition | Foundational human evidence established that **germline ABL1 variants cause an autosomal dominant syndrome characterized by congenital heart defects, skeletal abnormalities/malformations, dysmorphic features, and failure to thrive**. | Initial report: **6 affected individuals** from **4 families**. | Human clinical genetics, Nature Genetics 2017, doi:10.1038/ng.3815 (PMID linked in Open Targets as **28288113**) (pqac-00000002, pqac-00000003) |
| Inheritance | CHDSKM shows **autosomal dominant** inheritance with both **de novo** occurrence and vertical transmission/cosegregation in families. | 2017 series: **p.Tyr245Cys** occurred **de novo or cosegregated** in families 1-3; **p.Ala356Thr** was **de novo** in family 4. 2021 series: **5/6** new cases had **de novo confirmation**. | Human clinical genetics, Nature Genetics 2017 doi:10.1038/ng.3815; Eur J Hum Genet 2021 doi:10.1038/s41431-020-00766-w (pqac-00000002, pqac-00000008) |
| Molecular mechanism class | The disorder is best supported as an **ABL1 gain-of-function kinase syndrome**, not haploinsufficiency. Mutant proteins show increased tyrosine phosphorylation/kinase activity. | Increased phosphorylation of ABL1-specific substrates in HEK293T/HEK 293T assays for **p.Tyr245Cys, p.Ala356Thr**, and additional 2021 variants; 2024 biochemical work shows **E528K vmax ~202 vs WT ~89** (>2-fold), with **KM unchanged**. | Human variant functional assays and biochemical/structural studies, 2017/2021/2024 (doi:10.1038/ng.3815; doi:10.1038/s41431-020-00766-w; doi:10.1101/2023.10.04.560671) (pqac-00000001, pqac-00000007, pqac-00000015, pqac-00000021) |
| Variant spectrum | Reported pathogenic CHDSKM missense variants include **p.Tyr245Cys, p.Val244Ala, p.Ala356Thr, p.Ala452Thr, p.Val525Ala, p.Glu528Lys**. Several cluster in/near the kinase regulatory myristoyl-binding pocket. | 2017: **2 variants** (**c.734A>G p.Tyr245Cys**, **c.1066G>A p.Ala356Thr**). 2021: total **5 germline variants** listed as **c.731T>C p.Val244Ala**, **c.1066G>A p.Ala356Thr**, **c.1354G>A p.Ala452Thr**, **c.1574T>C p.Val525Ala**, **c.1582G>A p.Glu528Lys**. | Human clinical/variant interpretation studies, 2017 and 2021 (pqac-00000002, pqac-00000006) |
| Variant: Tyr245Cys | **p.Tyr245Cys** is a recurrent causal variant in the **SH2-kinase linker region** associated with CHDSKM and increased kinase signaling. | Seen in **5 individuals** across families 1-3 in the 2017 report; absent from dbSNP/ESP/ExAC/COSMIC in that study. | Human clinical genetics plus in vitro functional assay, Nature Genetics 2017 doi:10.1038/ng.3815 (PMID 28288113 via Open Targets) (pqac-00000002, pqac-00000007, pqac-00000009) |
| Variant: Val244Ala | **p.Val244Ala** is a de novo CHDSKM variant affecting the SH2-kinase linker/regulatory region and functionally increases ABL1 signaling. | Reported among the **6 new unrelated individuals** in 2021; described as **de novo**; functional assays showed increased STAT5B/overall tyrosine phosphorylation. | Human case series with in vitro functional validation, Eur J Hum Genet 2021 doi:10.1038/s41431-020-00766-w (pqac-00000004, pqac-00000008) |
| Variant: Ala356Thr | **p.Ala356Thr** is a de novo kinase-domain CHDSKM variant with increased kinase activity. | Present in **1 individual** in 2017 and also represented in 2021 aggregated variant list; increased phosphotyrosine and STAT5 phosphorylation in vitro. | Human clinical genetics and in vitro assay, 2017/2021 (pqac-00000002, pqac-00000006, pqac-00000013) |
| Variant: Ala452Thr | **p.Ala452Thr** is a CHDSKM-associated kinase-domain variant included in the expanded 2021 spectrum. | Listed among pathogenic/likely pathogenic variants in 2021; individual table excerpt notes growth, craniofacial, and cardiac findings in affected patient(s). | Human case series, Eur J Hum Genet 2021 doi:10.1038/s41431-020-00766-w (pqac-00000006, pqac-00000013) |
| Variant: Val525Ala | **p.Val525Ala** is a de novo variant in the **myristoyl-binding pocket/kinase domain** supporting the autoinhibition-loss model. | Included in 2021 five-variant set; one of the variants clustering in the myristoyl pocket. | Human case series with structural interpretation and kinase assay, Eur J Hum Genet 2021 doi:10.1038/s41431-020-00766-w (pqac-00000004, pqac-00000006) |
| Variant: Glu528Lys | **p.Glu528Lys (E528K)** is a de novo myristoyl-pocket/αI'-helix variant strongly linked to gain-of-function and later structural definition. | Included in 2021 case series as de novo; 2024 study shows disruption of the **E528-R479** salt bridge, increased core disassembly, and **>2-fold** activity increase. | Human case series + biochemical/structural mechanism, 2021/2024 (pqac-00000004, pqac-00000015, pqac-00000016, pqac-00000017) |
| Population frequency | Reported CHDSKM variants are extremely rare; the expanded 2021 series states all listed pathogenic variants were **absent from gnomAD**. | **5/5** listed 2021 variants absent from gnomAD; 2017 variants absent from dbSNP, ESP, ExAC, COSMIC. | Human variant interpretation, 2017 and 2021 (pqac-00000006, pqac-00000007) |
| Aggregated phenotype burden | Across the **18 reported cases** summarized in 2021, the most frequent findings were dysmorphic facies, digital anomalies, congenital heart disease, failure to thrive, developmental delay, IUGR, ear abnormalities, palatal deformity, and microcephaly. | **Dysmorphic facies 18/18 (100%)**; **finger/toe abnormalities 17/18 (94%)**; **congenital heart disease 14/18 (78%)**; **failure to thrive 14/18 (78%)**; **developmental delay 11/18 (61%)**; **IUGR 10/18 (56%)**; **ear abnormalities 9/18 (50%)**; **palatal deformity 9/18 (50%)**; **microcephaly 9/18 (50%)**. | Aggregated human case series, Eur J Hum Genet 2021 doi:10.1038/s41431-020-00766-w (pqac-00000005, pqac-00000012) |
| Cardiac phenotype | Cardiac disease is a cardinal manifestation; specific reported defects include septal defects, patent ductus arteriosus, supravalvular pulmonary stenosis, and aortic root dilatation. | CHD in **6/6** initial 2017 patients and **14/18** pooled cases by 2021. | Human clinical case reports/series, 2017 and 2021 (pqac-00000003, pqac-00000004, pqac-00000011, pqac-00000013) |
| Skeletal/limb phenotype | Skeletal/digital anomalies are pervasive and include scoliosis, pectus excavatum, hindfoot deformity, finger contractures, camptodactyly, clinodactyly, Dupuytren contracture, and toe syndactyly. | Skeletal abnormalities in **6/6** initial 2017 cohort; finger/toe abnormalities **17/18** pooled; camptodactyly noted in **5/6** in one excerpt from the 2021 cohort. | Human clinical case series, 2017/2021 (pqac-00000003, pqac-00000006, pqac-00000011, pqac-00000014) |
| Hearing | Hearing impairment appears to be a recurrent feature in the expanded syndrome. | 2021 cohort excerpt: hearing impairment **4/6** in the new series; authors state hearing impairment is a common feature. | Human clinical case series, Eur J Hum Genet 2021 doi:10.1038/s41431-020-00766-w (pqac-00000001, pqac-00000011, pqac-00000014) |
| Growth/development | Growth restriction and neurodevelopmental issues are common but variable. | Failure to thrive **14/18**; IUGR **10/18**; developmental delay **11/18**. 2017 series also reported failure to thrive in **5/6**. | Human clinical case series, 2017/2021 (pqac-00000003, pqac-00000012) |
| Other organ involvement | Additional reported manifestations include male genital anomalies, GI anomalies, renal hypoplasia, ocular abnormalities, and occasional other malformations. | 2017: hypospadias/hypogonadism **3/4 males**, pyloric muscle thickening **1/6**, imperforate anus **1/6**. 2021 abstract notes renal hypoplasia and ocular abnormalities in affected individuals. | Human clinical reports, 2017/2021 (pqac-00000009, pqac-00000010) |
| 2024 structural mechanism | The best current mechanistic explanation for **E528K** is disruption of the **E528-R479 salt bridge** at the end of the **αI'-helix**, increasing force on the SH2 domain, disassembling the SH3-SH2-kinase regulatory core, and activating kinase function. | 2024 study reports Pearson correlation between activity and imatinib-induced disassembly **r=0.89**; **vmax ~202 vs ~89** for WT, **KM unchanged**. | Biochemical/structural study, eLife 2024/preprint DOI 10.1101/2023.10.04.560671 (pqac-00000015, pqac-00000016, pqac-00000017, pqac-00000018) |
| Pharmacologic implication | In vitro, mutant hyperphosphorylation can be **suppressed by imatinib**; 2024 work also supports opposing effects of type II ATP-site inhibitors versus allosteric stabilization of the myristoyl pocket/αI-helix. | 2021: imatinib abolished phosphorylation across constructs. 2024: **asciminib** reduces activity by fixating the αI-helix, whereas type II inhibitors like imatinib promote core disassembly despite ATP-site inhibition. | Functional/structural pharmacology, 2021 and 2024 (pqac-00000001, pqac-00000008, pqac-00000018) |
| Diagnosis | Diagnosis has been established primarily by **clinical exome sequencing / whole exome sequencing** in individuals with syndromic CHD plus skeletal/dysmorphic features, followed by variant interpretation and, in research settings, functional testing. | 2017 and 2021 causal discoveries both relied on exome-based approaches; one 2022 ES study cited CHDSKM as a diagnosable syndromic entity in broader congenital anomaly testing. | Human diagnostic genomics studies, 2017/2021/2022 (pqac-00000003, pqac-00000001) |
| Management considerations | Published management suggestions are supportive and surveillance-based: assess congenital heart disease, consider **aortic root diameter screening**, and obtain **audiology assessment** because aortopathy/hearing issues recur. | Explicit 2021 recommendations mention **aortic root diameter screening at diagnosis** and **audiological assessment**; no disease-specific treatment outcomes reported. | Expert interpretation within human case series, Eur J Hum Genet 2021 doi:10.1038/s41431-020-00766-w (pqac-00000004) |
| Malignancy risk | Despite ABL1’s oncologic relevance, no hematologic malignancy was reported in available CHDSKM cases, though long-term surveillance has been suggested because evidence is sparse. | Reported CHDSKM cases with malignancy: **0** in available excerpts. | Human case series commentary, 2017/2021 (pqac-00000004, pqac-00000007) |
| Distinction from ABL1 deficiency | CHDSKM is **not** equivalent to biallelic ABL1 loss/deficiency. Available evidence supports **constitutional gain-of-function** in CHDSKM, while separate literature notes **biallelic loss-of-function ABL1 deficiency** is phenotypically distinct. | Distinction stated explicitly in 2023 diagnostic-pitfall literature; mouse **Abl1** knockout phenotypes (growth delay, cardiac hyperplasia, osteoporosis, lymphopenia, eye/head defects, perinatal lethality) differ from the human GOF syndrome. | Human genetics commentary plus model-organism evidence (pqac-00000009, pqac-00000011) |
| Evidence gaps | Major gaps remain: ultra-rare disease frequency/prevalence unknown; no validated biomarkers or formal diagnostic criteria; no disease-specific clinical trials; no robust natural-history, survival, QoL, penetrance, or genotype-response datasets. | Published evidence is based on roughly **18 aggregated human cases** by 2021 plus mechanistic follow-up; no interventional CHDSKM trial evidence was retrieved. | Synthesis of available human case series and lack of retrieved disease-specific trials (pqac-00000005, pqac-00000012) |


*Table: This table condenses the strongest currently retrieved evidence for ABL1-related congenital heart defects and skeletal malformations syndrome, including identifiers, inheritance, variant spectrum, pooled phenotype frequencies, mechanism, and management implications. It is useful as a curation-ready summary that also flags where evidence remains sparse or absent.*