| Disease / synonym(s) | Key identifiers explicitly supported in evidence | Causal gene / protein | Inheritance | Hallmark laboratory finding | Typical onset | Core phenotypes (with frequency when available) | Recurrent / founder or notable variants mentioned | Treatment and outcomes | Key references |
|---|---|---|---|---|---|---|---|---|---|
| Familial isolated vitamin E deficiency; Ataxia with isolated vitamin E deficiency (AVED); Ataxia with vitamin E deficiency (pqac-00000007, pqac-00000014) | OMIM/MIM **277460** explicitly stated for AVED (pqac-00000014); TTPA transcript/protein entry noted as **OMIM*600415** in one report (pqac-00000009) | **TTPA** encoding **α-tocopherol transfer protein (α-TTP / αTTP)**; α-TTP binds α-tocopherol and mediates incorporation into VLDL / circulating lipoproteins (pqac-00000009, pqac-00000011) | **Autosomal recessive**; biallelic / homozygous or compound heterozygous TTPA variants reported (pqac-00000008, pqac-00000014) | Markedly **low plasma/serum vitamin E (α-tocopherol)** despite intact intestinal absorption and otherwise normal lipids in reported cases; one snippet notes AVED levels should be **<1.7 mg/L** (pqac-00000000, pqac-00000002, pqac-00000008) | Usually **late childhood to early adolescence**; broader reported range from **early childhood/infancy to adulthood/fourth decade**; untreated disease often manifests **5–15 years** (pqac-00000008, pqac-00000009, pqac-00000014) | Friedreich-like phenotype with **progressive ataxia**, **areflexia/hyporeflexia**, loss of **proprioception/vibration sense**, **dysarthria**, sensory neuropathy; extra-neurologic/other features can include **head titubation/dystonia**, retinitis pigmentosa, scoliosis, cardiomyopathy. Frequency data from one review: absent tendon reflexes **94.7%**, gait disturbance **93.4%**, extensor plantar response **85.5%**, posterior column involvement **67.1%**, dysarthria **61.8%**, head titubation **40.8%**, retinitis pigmentosa **2.3%**, cardiomyopathy **1.5%** (pqac-00000010). Earlier cohort found cardiomyopathy **19%**, head titubation **28%**, dystonia **13%** (pqac-00000007). | Recurrent/founder variants mentioned: **c.744delA** major in **North Africa / Mediterranean** and associated with earlier/severe disease; **c.513_514insTT**, **c.486delT**, **c.400C>T (R134X)** in European-origin families; **H101Q** associated with milder, late-onset phenotype; additional reported variants include **c.205-1G>C**, **c.473C>T (p.F185S)**, **c.717delC (p.D239EfsX25)**, **c.58dupC (p.His20ProfsTer56)**, and a start-codon mutation in a Japanese family (pqac-00000000, pqac-00000007, pqac-00000008, pqac-00000009, pqac-00000011, pqac-00000014) | Lifelong **high-dose oral vitamin E** replacement. Reported recommendations/examples: **800–1500 mg/day** or about **40 mg/kg/day in children**; case regimens include **800 mg/day**, **400 mg three times daily**, **1,200 IU/day**, and **2,000 units/day**. Early treatment can **halt progression**, **stabilize** disease, and sometimes improve established neurologic abnormalities; delayed treatment may leave persistent proprioceptive/gait deficits (pqac-00000000, pqac-00000002, pqac-00000008, pqac-00000009, pqac-00000011, pqac-00000012, pqac-00000013) | Cavalier 1998, Am J Hum Genet, DOI: https://doi.org/10.1086/301699 (pqac-00000007); Hoshino 1999, Ann Neurol, DOI: https://doi.org/10.1002/1531-8249(199906)45:6<809::aid-ana19>3.0.co;2-9 (pqac-00000014); Iwasa 2014, J Neurol Sci, DOI: https://doi.org/10.1016/j.jns.2014.07.001 (pqac-00000011); Holla 2024, J Mov Disord, DOI: https://doi.org/10.14802/jmd.23227 (pqac-00000008) |


*Table: This table condenses the evidence-backed core facts for familial isolated vitamin E deficiency / AVED, including identifiers, genetics, phenotype, variants, and treatment. It is useful as a quick reference for knowledge-base population while limiting claims to those explicitly present in the provided snippets.*