| Topic | Key facts | Suggested ontology terms | Key references / evidence |
|---|---|---|---|
| Disease definition & synonyms | Rare hereditary ectodermal dysplasia primarily affecting teeth and nails; characterized by congenital tooth agenesis/hypodontia or oligodontia plus nail dysplasia. Common synonyms: **Witkop syndrome**, **tooth-and-nail syndrome (TNS)**, **hypodontia–nail dysplasia syndrome**, **Witkop tooth-and-nail syndrome**. Disease-level information is derived mainly from aggregated case reports/families and review resources, not EHR-scale datasets. (pqac-00000001, pqac-00000003, pqac-00000005) | MONDO: not confidently identified from available context; HPO candidates include **Hypodontia** HP:0000677, **Oligodontia** HP:0000676, **Abnormality of nails** HP:0001597 | Altug-Atac & Iseri 2008, *Angle Orthod* 78:370-380, DOI: 10.2319/100406-403.1, https://doi.org/10.2319/100406-403.1 (pqac-00000001); Memarpour & Shafiei 2011, *Pediatr Dermatol* 28:281-285, DOI: 10.1111/j.1525-1470.2010.01198.x, https://doi.org/10.1111/j.1525-1470.2010.01198.x (pqac-00000003) |
| Inheritance | Usually **autosomal dominant** with **variable expressivity**; family pedigrees show vertical transmission across generations. (pqac-00000001, pqac-00000003, pqac-00000011, pqac-00000013, pqac-00000016) | HPO: **Autosomal dominant inheritance** HP:0000006; **Variable expressivity** HP:0003828 | Jumlongras et al. 2001, *Am J Hum Genet* 69:67-74, DOI: 10.1086/321271, https://doi.org/10.1086/321271 (pqac-00000011, pqac-00000016); Cammarata-Scalisi et al. 2024, *Clin Oral Investig* 29:9, DOI: 10.1007/s00784-024-05941-7, https://doi.org/10.1007/s00784-024-05941-7 (pqac-00000013) |
| Causal gene & key pathogenic variant | Canonical causal gene from primary evidence: **MSX1** (OMIM gene cited in review context as 142983). Landmark family study identified heterozygous **c.605C>A, p.Ser202Ter (S202X)** nonsense variant in exon 2/homeodomain; variant cosegregated with disease and was absent from 132 control chromosomes. Evidence type: **human familial linkage + segregation + sequencing**, supported by **mouse model** phenotype parallels. (pqac-00000009, pqac-00000010, pqac-00000011, pqac-00000013) | HGNC gene: **MSX1**; Sequence ontology idea: **nonsense_variant**; HPO: **Abnormality of the dentition** HP:0000164 | Jumlongras et al. 2001, *Am J Hum Genet* 69:67-74, DOI: 10.1086/321271, https://doi.org/10.1086/321271 (pqac-00000009, pqac-00000010); 2024 summary review confirms **MSX1 → Witkop type ED3 (AD)** (pqac-00000013) |
| Core phenotype: teeth | Congenitally missing primary and/or permanent teeth; reported range in one pedigree **11-28 missing permanent teeth**. Frequently absent teeth reported across case literature include **mandibular incisors, second molars, maxillary canines/incisors**. Remaining teeth may be **small, widely spaced, conical/narrow-crowned**; retained primary teeth are common. (pqac-00000001, pqac-00000003, pqac-00000005, pqac-00000012, pqac-00000016) | HPO: **Hypodontia** HP:0000677; **Oligodontia** HP:0000676; **Conical tooth** HP:0000698; **Widely spaced teeth** HP:0000687; **Retained primary teeth** HP:0006335 | Devadas et al. 2005, *Int J Paediatr Dent* 15:364-369, DOI: 10.1111/j.1365-263x.2005.00647.x, https://doi.org/10.1111/j.1365-263x.2005.00647.x (pqac-00000005); Memarpour & Shafiei 2011 (pqac-00000003); Jumlongras et al. 2001 (pqac-00000012) |
| Core phenotype: nails | Fingernail and toenail dysplasia, often **more severe in toenails**; nails may be **thin, brittle, slow-growing, spoon-shaped (koilonychia), rigid**, with **onychorrhexis/longitudinal ridging**. Nail findings are often most obvious in childhood and may **improve with age**. (pqac-00000001, pqac-00000003, pqac-00000005, pqac-00000006, pqac-00000011, pqac-00000016) | HPO: **Nail dysplasia** HP:0002164; **Koilonychia** HP:0001802; **Onychorrhexis** HP:0033863; **Slow-growing nails** HP:0008388 | Altug-Atac & Iseri 2008 (pqac-00000001); Arora et al. 2016, *J Oral Biol Craniofac Res* 6:79-81, DOI: 10.1016/j.jobcr.2015.07.003, https://doi.org/10.1016/j.jobcr.2015.07.003 (pqac-00000006) |
| Other ectodermal features | Hair is usually **normal or only mildly affected** (fine/thin hair may occur); **sweat gland function is typically normal**, helping distinguish TNS from hypohidrotic ectodermal dysplasia. (pqac-00000001, pqac-00000003, pqac-00000005, pqac-00000012) | HPO: **Normal sweating** not usually encoded; possible phenotype if present: **Sparse hair** HP:0008070 | Memarpour & Shafiei 2011 (pqac-00000003); Devadas et al. 2005 (pqac-00000005) |
| Onset & course | Congenital/developmental disorder. Nail abnormalities may be noticed at birth or early childhood; diagnosis often becomes clearer around **4-5 years** when missing primary/permanent teeth are recognized radiographically/clinically. Course is **lifelong**, but nail severity may lessen with age; dental agenesis is non-progressive once established. (pqac-00000003, pqac-00000005, pqac-00000011) | HPO: **Congenital onset** HP:0003577; **Childhood onset** HP:0011463 | Devadas et al. 2005 (pqac-00000005); Jumlongras et al. 2001 (pqac-00000011) |
| Prevalence estimates reported | Published estimates in case/review literature vary: commonly cited **~1-2 per 10,000 births/newborns**; one case report cites **~1 in 100,000 live births**. These figures appear to be literature-derived estimates rather than registry-based epidemiology, so precision is uncertain. (pqac-00000001, pqac-00000003, pqac-00000005, pqac-00000006) | No specific ontology term | Altug-Atac & Iseri 2008 (1-2/10,000) (pqac-00000001); Memarpour & Shafiei 2011 (1-2/10,000) (pqac-00000003); Arora et al. 2016 (1/100,000) (pqac-00000006) |
| Diagnostic approach | Diagnosis is primarily **clinical + dental radiography + family history**, with confirmation by **molecular testing of MSX1** when available. Panoramic radiography/OPG documents tooth agenesis; pedigree analysis supports AD inheritance. Differential diagnosis includes **Fried tooth-and-nail syndrome**, **trichoonychodental syndrome**, and **Clouston syndrome**. (pqac-00000000, pqac-00000001, pqac-00000007, pqac-00000016) | HPO: **Family history** not a phenotype; possible MAXO ideas for downstream curation: genetic counseling/testing terms | Bhardwaj 2023 case report (clinical exam + OPG) (pqac-00000000, pqac-00000007); Altug-Atac & Iseri 2008 (pqac-00000001) |
| Management / real-world implementation | No disease-specific pharmacotherapy. Real-world care is **multidisciplinary dental rehabilitation**: preventive dental care, space management/orthodontics, prosthodontics, retention of primary teeth when useful to preserve alveolar bone, and implants after growth completion in selected patients; simple nail care and psychosocial support are recommended. A 2023 familial case series reported **surgical/prosthetic rehabilitation using zygomatic implants with up to 15-year follow-up** (identified in search results, full text not retrieved here). (pqac-00000000, pqac-00000002, pqac-00000007) | MAXO suggestions for downstream use: dental prosthesis placement, orthodontic treatment, genetic counseling; HPO impact terms may include **Abnormality of dental occlusion** HP:0000689 | Devadas et al. 2005 (preventive/prosthetic strategy) (pqac-00000002); Bhardwaj 2023 (multidisciplinary care, nail care, counseling) (pqac-00000007) |
| Recent developments / latest research | Disease-specific 2023-2024 primary TNS literature appears sparse. A **2024 review on tooth agenesis** reaffirms **MSX1** as the gene for **Witkop-type ectodermal dysplasia (AD)**. Broader mechanistic work remains relevant: MSX1 developmental role and earlier molecular proof remain the main authoritative evidence base. (pqac-00000013) | HGNC: MSX1; MONDO placeholder pending confirmation | Cammarata-Scalisi et al. 2024, *Clin Oral Investig* 29:9, DOI: 10.1007/s00784-024-05941-7, https://doi.org/10.1007/s00784-024-05941-7 (pqac-00000013) |


*Table: This table compiles the core disease facts for Tooth and Nail Syndrome (Witkop syndrome), including inheritance, MSX1 molecular evidence, key phenotypes, onset, prevalence estimates, and practical diagnostic/management points. It is designed as a compact reference for knowledge-base curation and evidence mapping.*