| Domain | Key finding | Suggested ontology/ID(s) | Evidence type | Citation |
|---|---|---|---|---|
| Disease identifier | Sinoatrial node dysfunction and deafness (SANDD); ultra-rare Mendelian channelopathy caused by CACNA1D loss of function; MONDO disease mapping available | MONDO:0013960; OMIM:614896 | Established human disease mapping | (pqac-00000000, pqac-00000006) |
| Synonyms | SANDD; sino-atrial node dysfunction and deafness; sinus node dysfunction and deafness | MONDO:0013960 | Aggregated disease resource + literature | (pqac-00000000, pqac-00000010) |
| Causal gene | CACNA1D encodes CaV1.3/L-type voltage-gated calcium channel alpha1D, the only consistently implicated disease gene | HGNC:1392; Ensembl:ENSG00000157388 | Established human genetics | (pqac-00000000, pqac-00000006) |
| Core molecular mechanism | Biallelic CACNA1D loss of function abolishes or markedly reduces CaV1.3-mediated inward Ca2+ current in sinoatrial/atrioventricular nodal cells and cochlear inner hair cells, impairing pacemaking and auditory transduction/development | GO:0005245 voltage-gated calcium channel activity; GO:0060048 cardiac muscle contraction?; GO:0086001 cardiac muscle cell action potential; GO:0006816 calcium ion transport | Human functional inference supported by model/heterologous data | (pqac-00000008, pqac-00000009, pqac-00000012, pqac-00000013) |
| Pathogenic variants | Recurrent SANDD variant reported as p.Gly403dup / p.403_404insGly / p.403-404InsGly (3-bp insertion in alternatively spliced exon 8B); another reported SANDD-associated missense variant p.Ala376Val | HGVS protein: p.Gly403dup; p.Ala376Val | Established human variant-level evidence | (pqac-00000006, pqac-00000008, pqac-00000009) |
| Variant effect | p.Gly403dup mutant channels traffic to plasma membrane but are electrically silent/non-conducting; likely uncouples gating from pore opening or sterically impairs ion permeation | GO:1901385 regulation of membrane depolarization? | Human mutation with in vitro functional evidence | (pqac-00000008, pqac-00000009) |
| Inheritance | Autosomal recessive / biallelic disease; heterozygous relatives reported as clinically unaffected in classic SANDD families | HP:0000007 Autosomal recessive inheritance | Established human pedigree evidence | (pqac-00000008, pqac-00000009) |
| Population / founder context | Reported in seven consanguineous Pakistani families from Khyber Pakhtunkhwa province; indicates strong founder/consanguinity contribution in known cases | HP:0003765 Increased consanguinity | Established human family-series evidence | (pqac-00000006, pqac-00000009) |
| Epidemiology | No robust prevalence or incidence estimates identified; evidence limited to a handful of families/case reports | MONDO:0013960 | Evidence gap | (pqac-00000006, pqac-00000009) |
| Cardiac phenotype | Severe sinus bradycardia, sinus node dysfunction, sinus pauses, SAN exit block, atrioventricular conduction disease ranging from 2nd-degree AV block to complete heart block; exercise-related dizziness/fatigue/syncope reported | HP:0001649 Bradycardia; HP:0001677 Cardiac syncope; HP:0011706 Second degree atrioventricular block; HP:0004762 Complete atrioventricular block | Established human clinical evidence | (pqac-00000008) |
| Quantitative cardiac data | Reported daytime heart rates ~38-52 bpm and nocturnal heart rates below 35 bpm in homozygous affected individuals | HP:0001649 Bradycardia | Established human quantitative evidence | (pqac-00000008) |
| Auditory phenotype | Congenital/profound sensorineural deafness or hearing loss is a defining feature of classic SANDD | HP:0000407 Sensorineural hearing impairment; HP:0008619 Congenital hearing impairment | Established human clinical evidence | (pqac-00000001, pqac-00000012) |
| Typical onset/course | Congenital or early-life onset for deafness; cardiac conduction disease present in childhood and appears chronic/lifelong rather than remitting | HP:0003577 Congenital onset | Human cases + inference from syndrome description | (pqac-00000001, pqac-00000008, pqac-00000012) |
| Key affected organs | Heart conduction system and inner ear/cochlea are primary organs directly affected | UBERON:0000948 heart; UBERON:0001844 inner ear; UBERON:0001690 cochlea | Established from human and model evidence | (pqac-00000008, pqac-00000012, pqac-00000013) |
| Key tissues/cells | Sinoatrial node pacemaker cells, atrioventricular nodal cells, cochlear inner hair cells | UBERON:0000079 sinoatrial node; UBERON:0000086 atrioventricular node; CL:0000586 hearing receptor cell; inner hair cell term not asserted with confidence | Human/mechanistic/model evidence | (pqac-00000007, pqac-00000009, pqac-00000012) |
| SAN electrophysiology | CaV1.3 activates at more negative voltages than CaV1.2 (about -45 mV vs -25 mV), contributing directly to diastolic depolarization; under beta-adrenergic stimulation threshold may extend to about -55 to -60 mV | GO:0086012 membrane depolarization during cardiac muscle cell action potential | Mechanistic evidence from experimental studies summarized in reviews | (pqac-00000009, pqac-00000011) |
| Upstream/downstream causal chain | CACNA1D LoF -> reduced nodal diastolic inward Ca2+ current and impaired RyR2/NCX-coupled pacemaker activity -> slowed SAN automaticity and AV conduction -> bradycardia, pauses, syncope; CACNA1D LoF in inner hair cells -> absent L-type Ca2+ signaling and arrested maturation/degeneration -> congenital deafness | GO:0006936 muscle contraction process not specific; GO:0001508 action potential; GO:0006816 calcium ion transport | Mechanistic synthesis from human, in vitro, and model evidence | (pqac-00000008, pqac-00000009, pqac-00000011, pqac-00000013) |
| Diagnostics: clinical | ECG/Holter monitoring for sinus bradycardia, pauses, SAN exit block, and AV block; audiologic testing for congenital sensorineural deafness; family history and consanguinity assessment are relevant | LOINC/ECG not asserted; HP:0001649; HP:0000407 | Established clinical practice inference from reported phenotypes | (pqac-00000008, pqac-00000010) |
| Diagnostics: genetic | Priority testing methods: CACNA1D single-gene analysis if syndrome suspected; broader arrhythmia/deafness panels, WES/WGS if phenotype nonspecific; testing should distinguish recessive LoF SANDD from dominant CACNA1D gain-of-function neurodevelopmental syndromes | HGNC:1392; MONDO:0013960 | Expert/clinical inference anchored in known gene-disease relationship | (pqac-00000000, pqac-00000001, pqac-00000002) |
| Management | No disease-specific drug therapy established; symptomatic management centers on pacemaker implantation for clinically significant sinus node dysfunction/conduction disease; hearing rehabilitation may include hearing aids/cochlear implant based on audiology, though syndrome-specific outcome data are lacking | NCIT:C17754 Cardiac Pacemaker Implantation | Standard-of-care inference + SND review evidence | (pqac-00000010, pqac-00000008) |
| Prognosis | Morbidity likely driven by chronic bradyarrhythmia/syncope and lifelong deafness; syndrome-specific survival, QoL, and natural-history statistics not identified | MONDO:0013960 | Evidence gap with cautious inference | (pqac-00000008, pqac-00000010) |
| Distinction from other CACNA1D disorders | Classic SANDD is biallelic loss-of-function with deafness and nodal disease; distinct from heterozygous CACNA1D disorders such as dominant mixed LoF/GoF sinus node dysfunction with epilepsy (p.Arg930His) and de novo gain-of-function neurodevelopmental/endocrine syndromes, which may lack deafness | MONDO:0013960 | Established genotype-phenotype distinction | (pqac-00000001, pqac-00000002, pqac-00000004, pqac-00000014) |
| Animal model: global knockout | Cacna1d/CaV1.3-null mice recapitulate bradycardia, sinoatrial dysfunction, AV block, and deafness; useful for mechanism and therapeutic proof-of-concept | NCBITaxon:10090 | Established model-organism evidence | (pqac-00000007, pqac-00000008, pqac-00000010, pqac-00000013) |
| Quantitative model data | Global CaV1.3 knockout mice show ~60-70% reduction in SAN ICa,L density | GO:0005245 | Model quantitative evidence | (pqac-00000007) |
| Auditory model findings | Systemic and cochlea-specific Cacna1d deletion causes profound hearing loss; inner hair cells remain immature with absent BK upregulation and persistent SK2 expression; degeneration can occur in systemic null mice | GO:0042491 inner ear auditory receptor cell differentiation; GO:0005249 voltage-gated potassium channel activity | Established model evidence | (pqac-00000012) |
| Experimental therapy signals | In mice, IKACh inhibition rescued bradycardia/automaticity in CaV1.3 channelopathy models; this is preclinical and not established for human SANDD | NCIT not asserted; GO:0005227 calcium-activated cation channel activity not specific | Model/preclinical evidence | (pqac-00000010, pqac-00000011) |
| Recent developments (2023-2024) | Recent reviews emphasize CaV1.3 as a nodal-specific therapeutic target and summarize new CACNA1D variant models; 2024 isradipine work pertains to CACNA1D gain-of-function neurodevelopmental/endocrine disease, not SANDD loss of function | MONDO:0013960 | Recent expert analysis; indirect relevance | (pqac-00000005, pqac-00000014) |
| Environmental / infectious factors | No convincing environmental, lifestyle, toxin, or infectious causes identified for classic SANDD; gene-environment and epigenetic modifiers remain unproven | Not applicable | Evidence gap | (pqac-00000006, pqac-00000008) |
| Data provenance | Information derives from aggregated disease/gene resources plus a very small number of human families and supporting in vitro/mouse studies, not EHR-scale cohorts | MONDO:0013960 | Evidence appraisal | (pqac-00000000, pqac-00000006, pqac-00000010) |


*Table: This table condenses the most actionable disease-knowledge elements for Sinoatrial Node Dysfunction and Deafness, including identifiers, gene-mechanism links, phenotypes, models, and explicit evidence gaps. It is designed for direct knowledge-base extraction while separating established human evidence from model-supported inference.*