Each column keeps its native condition scope. Initial features are displayed alphabetically, not ranked by clinical importance. Counts remain separate, and an empty cell does not mean a feature cannot occur.
"},"coverage":{"countRecords":6,"emptyColumnKeys":[],"hpoRelease":"2026-06-23","narrativeSourceChanges":[],"records":10,"sourceGroups":{"omim":1,"orphanet":0,"published":9}},"features":[{"hpoId":"HP:0030479","label":"Abnormal amplitude of light-adapted flicker electroretinogram","primary":false},{"hpoId":"HP:0007642","label":"Early-onset non-progressive night blindness","primary":false},{"hpoId":"HP:0007984","label":"ERG: Reduced dark-adapted b-wave amplitude","primary":false},{"hpoId":"HP:0000577","label":"Exotropia","primary":false},{"hpoId":"HP:0012047","label":"Hemeralopia","primary":false},{"hpoId":"HP:0011003","label":"High myopia","primary":false},{"hpoId":"HP:0000639","label":"Nystagmus","primary":false},{"hpoId":"HP:0007663","label":"Reduced visual acuity","primary":false},{"hpoId":"HP:0000505","label":"Visual impairment","primary":false}],"ledeHtml":"X-linked congenital stationary night blindness is a disorder of the retina, which is a specialized tissue at the back of the eye that detects light and color. People with this condition typically have difficulty seeing in low light (night blindness). They also have other vision problems, including increased sensitivity to light (photophobia), loss of sharpness (reduced visual acuity), severe nearsightedness (high myopia), involuntary movements of the eyes (nystagmus), and eyes that do not look in the same direction (strabismus). Color vision is typically not affected in people with X-linked congenital stationary night blindness.","mondoId":"MONDO:0044749","records":[{"frequencyKind":"reported","key":"1dd3724f18bd47c473a194ef88c14b2e08cba62f2cea0ad6e49f6d5f1d4d4d40","raw":{"aspect":"P","body_system":"eye","disease_id":"OMIM:300071","disease_name":"Night blindness, congenital stationary, type 2A","evidence":"PCS","frequency_raw":null,"hpo_id":"HP:0030479","is_excluded":false,"label":"Abnormal amplitude of light-adapted flicker electroretinogram","onset_id":null,"reference":"PMID:9662399","source_release":"2026-06-23"},"sourceGroups":["published"]},{"frequencyKind":"count","key":"33477568fa76154cb15435feb3956863f2b39612768563f6f589b64b53651570","raw":{"aspect":"P","body_system":"eye","disease_id":"OMIM:310500","disease_name":"Night blindness, congenital stationary, type 1A","evidence":"PCS","frequency_raw":"5/5","hpo_id":"HP:0007642","is_excluded":false,"label":"Early-onset non-progressive night blindness","onset_id":null,"reference":"PMID:16670814","source_release":"2026-06-23"},"sourceGroups":["published"]},{"frequencyKind":"count","key":"44e5ba8e4866128dfe109e865e6cf6aa71425318c8d5d71c2b3dfd82f543e1f2","raw":{"aspect":"P","body_system":"eye","disease_id":"OMIM:300071","disease_name":"Night blindness, congenital stationary, type 2A","evidence":"PCS","frequency_raw":"7/7","hpo_id":"HP:0007663","is_excluded":false,"label":"Reduced visual acuity","onset_id":null,"reference":"PMID:9662399","source_release":"2026-06-23"},"sourceGroups":["published"]},{"frequencyKind":"reported","key":"45b063795b34698bd067d443119622cff12425596db186336a9e79b7abc1e20a","raw":{"aspect":"P","body_system":"eye","disease_id":"OMIM:310500","disease_name":"Night blindness, congenital stationary, type 1A","evidence":"TAS","frequency_raw":null,"hpo_id":"HP:0012047","is_excluded":false,"label":"Hemeralopia","onset_id":null,"reference":"OMIM:310500","source_release":"2026-06-23"},"sourceGroups":["omim"]},{"frequencyKind":"count","key":"73abf4b4e07030ab307c85107331faceb6e74220e81a4d1f0ad958fdbbc8b745","raw":{"aspect":"P","body_system":"eye","disease_id":"OMIM:310500","disease_name":"Night blindness, congenital stationary, type 1A","evidence":"PCS","frequency_raw":"4/5","hpo_id":"HP:0011003","is_excluded":false,"label":"High myopia","onset_id":null,"reference":"PMID:16670814","source_release":"2026-06-23"},"sourceGroups":["published"]},{"frequencyKind":"reported","key":"8e12fd1c92728886b9e81e0cd68e50c9334f018a24e0edebac5ce913268becc9","raw":{"aspect":"P","body_system":"eye","disease_id":"OMIM:300071","disease_name":"Night blindness, congenital stationary, type 2A","evidence":"PCS","frequency_raw":null,"hpo_id":"HP:0000505","is_excluded":false,"label":"Visual impairment","onset_id":null,"reference":"PMID:9662399","source_release":"2026-06-23"},"sourceGroups":["published"]},{"frequencyKind":"reported","key":"ae01dae59b5c20b887e52969a386601bb1818444cac99c1d9716c0ccbe51cef5","raw":{"aspect":"P","body_system":"eye","disease_id":"OMIM:300071","disease_name":"Night blindness, congenital stationary, type 2A","evidence":"PCS","frequency_raw":null,"hpo_id":"HP:0007642","is_excluded":false,"label":"Early-onset non-progressive night blindness","onset_id":null,"reference":"PMID:9662399","source_release":"2026-06-23"},"sourceGroups":["published"]},{"frequencyKind":"count","key":"c62b2fc255976b9dc8ffacd774468448ce58471af06c2589519a74058b57ef51","raw":{"aspect":"P","body_system":"eye","disease_id":"OMIM:300071","disease_name":"Night blindness, congenital stationary, type 2A","evidence":"PCS","frequency_raw":"7/7","hpo_id":"HP:0007984","is_excluded":false,"label":"ERG: Reduced dark-adapted b-wave amplitude","onset_id":null,"reference":"PMID:9662399","source_release":"2026-06-23"},"sourceGroups":["published"]},{"frequencyKind":"count","key":"d54abaf57db3f8191f03f9ea35e4dd38e9ec3a6d66531aef4d0ee611fe10b877","raw":{"aspect":"P","body_system":"eye","disease_id":"OMIM:300071","disease_name":"Night blindness, congenital stationary, type 2A","evidence":"PCS","frequency_raw":"2/7","hpo_id":"HP:0000577","is_excluded":false,"label":"Exotropia","onset_id":null,"reference":"PMID:9662399","source_release":"2026-06-23"},"sourceGroups":["published"]},{"frequencyKind":"count","key":"e4e6897081750644975d1a1d24df32beea84c5fcfe78a14b70310a6d78834844","raw":{"aspect":"P","body_system":"eye","disease_id":"OMIM:300071","disease_name":"Night blindness, congenital stationary, type 2A","evidence":"PCS","frequency_raw":"4/7","hpo_id":"HP:0000639","is_excluded":false,"label":"Nystagmus","onset_id":null,"reference":"PMID:9662399","source_release":"2026-06-23"},"sourceGroups":["published"]}],"referenceLabels":{},"references":{"causeHtml":"","identityNote":"MONDO cross-references identify native condition entries. Ancestor membership does not transfer phenotype values between groups.","importantHtml":""},"sections":[{"bodyHtml":"Variants (also called mutations) in the NYX gene cause the complete form of X-linked congenital stationary night blindness, and variants in the CACNA1F gene cause the incomplete form. The proteins produced from these genes play critical roles in the retina.
Within the retina, the CACNA1F protein is located on light-detecting cells called photoreceptors. The NYX protein is located on cells called bipolar cells, which relay signals to other retinal cells. The retina contains two types of photoreceptor cells: rods and cones. Rods are needed for vision in low light. Cones are needed for vision in bright light, including color vision. The NYX and CACNA1F proteins ensure that visual signals are passed from rods and cones to bipolar cells, which is an essential step in the transmission of visual information from the eyes to the brain.
Variants in the NYX or CACNA1F gene disrupt the transmission of visual signals between photoreceptors and bipolar cells, which impairs vision. In people with the complete form of X-linked congenital stationary night blindness, the rod pathway is severely disrupted, while the cone pathway is only mildly affected. In people with the incomplete form of the condition, the rod and cone pathways are both affected, although the affected person does have the ability to detect some light.
A particular variant in the CACNA1F gene has been found to cause X-linked congenital stationary night blindness in individuals who are of Dutch-German Mennonite descent. Similarly, certain NYX gene variants appear to be a frequent cause of X-linked congenital stationary night blindness in people who live in the United States and in people who live in Belgium and are of Flemish descent.
","key":"forms","title":"What causes X-linked congenital stationary night blindness?"},{"bodyHtml":"The vision problems associated with X-linked congenital stationary night blindness are congenital, which means they are present from birth. The vision problems also tend to remain stable (stationary) over time.
Researchers have identified two major types of X-linked congenital stationary night blindness: the complete form and the incomplete form. The types have very similar signs and symptoms. However, everyone with the complete form has night blindness, while not all people with the incomplete form have night blindness. The types are distinguished by their genetic causes and by the results of a test called an electroretinogram, which measures the function of the retina.
Source: MedlinePlus Genetics
","key":"overview","title":"Condition overview"}],"sharedSources":[],"slug":"x-linked-congenital-stationary-night-blindness","sourceDocuments":[{"name":"X-linked congenital stationary night blindness","reviewed":"2024-06","sections":{"causes":{"fetchedAt":"2026-10-20T20:25:55.228103+00:00","label":"Causes","pageSha256":"14d9459a2ed78545a0dc153c06dacbf450cbf228452a0874aea685bc281f0210","sourceUrl":"https://medlineplus.gov/genetics/condition/x-linked-congenital-stationary-night-blindness/#causes","status":"available"}},"source_release":"2026-10-01","url":"https://medlineplus.gov/genetics/condition/x-linked-congenital-stationary-night-blindness"}],"sourceNote":"MedlinePlus descriptions and Causes; original HPO annotations.","takeawayHtml":"Cause explanations are from MedlinePlus Genetics. Feature values below retain their original sources and patient groups.","title":"X-linked congenital stationary night blindness"},"schemaVersion":1}