| Domain | Established findings | Quantitative evidence | Suggested ontology terms | Evidence limitations |
|---|---|---|---|---|
| Disease scope / identifiers | KCNH1-associated disorder is best treated as a dominant KCNH1-related neurodevelopmental potassium-channelopathy spectrum that includes Temple-Baraitser syndrome (TMBTS), KCNH1-related Zimmermann-Laband syndrome type 1 (ZLS1), syndromic developmental delay/hypotonia/seizures, and milder isolated epilepsy. Distinguish from ATP6V1B2-related ZLS2 and KCNN3-related ZLS3. Open Targets supports associations with Temple-Baraitser syndrome and Zimmermann-Laband syndrome. (pqac-00000008, pqac-00000017, pqac-00000020, pqac-00000000) | Open Targets evidence size: 5 for Temple-Baraitser syndrome and 5 for Zimmermann-Laband syndrome; association scores ~0.79-0.80. (pqac-00000000) | MONDO_0000200 Zimmermann-Laband syndrome; EFO_0009062 Temple-Baraitser syndrome; NCIT: potassium channelopathy | No single universally adopted MONDO term for the full KCNH1 spectrum was retrieved; nomenclature varies across reports. |
| Inheritance / genetics | Predominantly heterozygous missense KCNH1 variants with autosomal dominant effect, usually de novo; inherited, mosaic, and somatic variants also occur and are often associated with milder or more focal phenotypes. Gain-of-function is the main pathogenic mechanism; truncating variants appear less consistently pathogenic. (pqac-00000001, pqac-00000003, pqac-00000004, pqac-00000012, pqac-00000015) | In aggregated review of 51 patients: 42/51 had epilepsy; 38/51 had de novo variants; 13/51 had non-de novo variants; 49/51 (96%) harbored missense variants. In an ID cohort, de novo pathogenic KCNH1 variants were found in 4/1447 individuals (0.3%). (pqac-00000004, pqac-00000015, pqac-00000018) | HGNC: KCNH1; SO: missense_variant, stop_gained, somatic_variant; HPO: HP:0000006 Autosomal dominant inheritance | Formal penetrance estimates are unavailable; low penetrance is suggested for p.Arg535* from family observations only. |
| Core phenotypes | Core syndromic findings include developmental delay/intellectual disability, epilepsy/seizures, hypotonia, coarse facial features, gingival enlargement, distal digital/terminal phalangeal and nail hypoplasia, and occasional hypertrichosis. Milder isolated febrile seizures/epilepsy without classic dysmorphism also occur. (pqac-00000008, pqac-00000011, pqac-00000013, pqac-00000015, pqac-00000020) | Among dominant KCNH1 cases summarized by Gripp et al.: absent/hypoplastic great toe nail 24/27 (89%); other finger/toe nail anomalies 16/20 (80%); gingival enlargement 15/19 (79%); hypertrichosis 3/16 (19%); hypoplasia of terminal phalanges 76%; proximal placement/long thumb 78%; long great toes 63%; broad thumb/toe 46%. Epilepsy/seizures in 82% of 51 reported patients. (pqac-00000011, pqac-00000015) | HPO: HP:0001263 Global developmental delay; HP:0001249 Intellectual disability; HP:0001250 Seizure; HP:0001290 Generalized hypotonia; HP:0000212 Gingival overgrowth; HP:0001558 Hypertrichosis; HP:0010808 Nail dysplasia; HP:0009882 Short distal phalanx of toe | Frequencies come from pooled case reports/reviews with missing data denominators; phenotype ascertainment is heterogeneous. |
| Mechanism / pathophysiology | Functional evidence supports pathogenic gain-of-function in Kv10.1/Eag1, with epilepsy-linked hotspots enriched in S4 and S6. KCNH1 localizes to the ciliary base/ciliary pocket; activating variants perturb cilia morphology, assembly/disassembly, intraflagellar transport, and SHH signaling, providing a developmental mechanism beyond excitability alone. (pqac-00000004, pqac-00000015, pqac-00000016, pqac-00000017, pqac-00000022) | Nine missense mutations showed gain-of-function electrophysiologic effects in prior studies summarized by Napoli et al.; in Tian et al., hotspot variants associated with epilepsy clustered in S4/S6, whereas milder non-epilepsy variants were more scattered. (pqac-00000015, pqac-00000016) | GO: potassium ion transmembrane transport; GO: regulation of membrane potential; GO: cilium assembly; GO: cilium organization; GO: Hedgehog signaling pathway; CL: neuron; CL: fibroblast; UBERON: primary cilium | Mechanistic evidence is largely in vitro and inferential; no direct in vivo KCNH1 disease model was retrieved. |
| Diagnosis | Diagnosis relies on syndrome recognition plus molecular testing, especially trio-WES/WES, with Sanger confirmation in reported cases. EEG and brain MRI help characterize seizures/complications; some patients have normal MRI/EEG early, whereas severe cases show diffuse slowing, subclinical temporal seizures, acute encephalopathy changes, or corpus callosum anomalies. (pqac-00000013, pqac-00000015, pqac-00000018, pqac-00000020, pqac-00000021) | In Tian et al., 98 patients with unexplained epilepsy/familial febrile seizures were screened and 2 KCNH1 missense variants were identified in 3 individuals. Case series report seizure onset from neonatal period to adolescence; newly reported isolated-epilepsy cases began at 8 months to 1.5 years. (pqac-00000002, pqac-00000010, pqac-00000013) | NCIT: Whole Exome Sequencing; HPO: HP:0002353 EEG abnormality; HP:0410018 Abnormal brain MRI; HP:0001250 Seizure | No standardized disease-specific diagnostic criteria or biomarker panel was retrieved; evidence is from case reports/series. |
| Treatment / management | Management is symptomatic: antiseizure medications (ASMs) are mainstay for epilepsy; gingivectomy/gingivoplasty and dental rehabilitation are used for severe gingival overgrowth. Reported ASMs include valproate, diazepam, phenobarbital, midazolam, carbamazepine, phenytoin, levetiracetam, lamotrigine, clobazam, sulthiame, lacosamide, oxcarbazepine; cannabidiol was reported effective in at least one case. (pqac-00000010, pqac-00000013, pqac-00000018, pqac-00000019, pqac-00000020, pqac-00000021) | More than half of epilepsy patients responded well to ASMs: 20/34 (59%). Case 3 in Tian et al. became seizure-free on valproate after refractory febrile seizures required IV midazolam. Dental surgery in a 2-year-old ZLS case improved mastication/lip closure, with slight recurrence at 2-year follow-up. (pqac-00000004, pqac-00000013, pqac-00000019, pqac-00000020, pqac-00000021) | NCIT: Anticonvulsant Therapy; NCIT: Valproic Acid; NCIT: Midazolam; NCIT: Gingivectomy; NCIT: Gingivoplasty | No KCNH1-targeted therapy, approved precision treatment, or interventional trial was retrieved. Reported responses are anecdotal/case-based. |
| Prognosis / outcomes | Outcomes are highly variable: some patients have mild isolated febrile seizures with normal cognition, whereas others develop severe DEE, regression, gait impairment, status epilepticus, acute encephalopathy, or death. Non-de novo/inherited or mosaic variants tend to be milder on average. (pqac-00000001, pqac-00000007, pqac-00000013, pqac-00000015, pqac-00000019) | Status epilepticus occurred in 21% of reported patients; 2 newly reported patients developed super-refractory SE. One newly reported patient died 20 days after seizure onset due to uncontrollable seizures and severe brain damage. (pqac-00000013, pqac-00000014, pqac-00000019) | HPO: HP:0002349 Status epilepticus; HP:0002376 Developmental regression; HP:0001252 Hypotonia; HP:0012378 Poor prognosis | No formal survival curves, life-expectancy estimates, or validated quality-of-life studies were retrieved. |
| Epidemiology / population | The disorder is very rare and currently described through aggregated case reports, case series, and review cohorts rather than population registries. Cases are reported across multiple ancestries and both sexes. (pqac-00000008, pqac-00000018, pqac-00000020) | Largest aggregated dataset cited here includes 51 patients with KCNH1 variants; another review summarized 27 dominant KCNH1 syndromic cases. No prevalence or incidence estimates were retrieved. (pqac-00000011, pqac-00000015) | NCIT: Rare Disease | No population-based prevalence, incidence, carrier frequency, founder effect, or sex-ratio data were found. |
| Model / experimental systems | Experimental support comes from in vitro systems: Xenopus laevis oocytes, HEK293T cells, CHO cells, human dermal fibroblasts, and hTERT-RPE1 cells. These show altered channel gating and ciliary defects for pathogenic missense variants. (pqac-00000004, pqac-00000016, pqac-00000017) | Functional studies summarized for 9 missense variants indicate increased whole-cell K+ conductance at negative potentials; Napoli et al. demonstrated abnormal cilia morphology and SHH-related defects in patient/mutant cell systems. (pqac-00000016) | CL: fibroblast; CL: retinal pigment epithelial cell; GO: voltage-gated potassium channel activity | No dedicated mammalian or zebrafish KCNH1 disease model with recapitulated syndrome-level phenotype was retrieved from the gathered evidence. |


*Table: This table condenses the current evidence base for KCNH1-associated disorder across clinical, genetic, mechanistic, diagnostic, and management domains. It is useful for rapid knowledge-base population because it highlights established findings, numeric evidence, ontology suggestions, and major evidence gaps.*