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Huntington's disease-like
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Condition

Huntington's disease-like

Huntington's disease-like (HDL) is a group of rare neurological conditions that resemble Huntington's disease, characterized by uncontrolled movements, emotional problems, and a decline in thinking ability.

Overview

HDLs occur in people who display the characteristic features of Huntington's disease but do not have a variant in the gene typically associated with that disorder. Researchers have described four types, designated HDL1 through HDL4. Sometimes, HDL4 is also known as spinocerebellar ataxia type 17 (SCA17).

Symptoms

HDL1, HDL2, and HDL4 usually begin in early to mid-adulthood. Common symptoms include:

  • Irritability and emotional problems
  • Small involuntary movements (dyskinesia)
  • Poor coordination and trouble learning or making decisions
  • Chorea (involuntary jerking or twitching movements)
  • Problems with walking (bradykinesia), speaking (dysarthria), and swallowing (dysphagia)
  • Changes in personality and decline in thinking abilities (dementia)

HDL3 begins much earlier in life, usually around age 3 or 4, and is characterized by a decline in thinking ability, movement and speech difficulties, and seizures.

Causes

Variants in the PRNP, JPH3, and TBP genes cause the various HDLs. These genes provide instructions for making proteins important for normal brain function. The variants involve an increase in the length of repeated DNA segments, leading to the production of abnormal proteins that build up in neurons and disrupt their function.

Genes Associated with Huntington's disease-like

  • JPH3
  • PRNP
  • TBP

Inheritance

HDL1, HDL2, and HDL4 are inherited in an autosomal dominant pattern, meaning one copy of the altered gene is sufficient to cause the disorder. HDL2 and HDL4 often exhibit anticipation, where the condition begins earlier and symptoms become more severe in successive generations. HDL3 is likely inherited in an autosomal recessive pattern, requiring two copies of the altered gene.

Frequently Asked Questions

No cure exists, but symptom management mirrors Huntington’s disease care: antichorea agents (tetrabenazine, deutetrabenazine), mood stabilizers or antidepressants for psychiatric issues, speech and occupational therapy for dysarthria and coordination problems, and swallowing assessments to prevent aspiration. Clinical trials of antisense oligonucleotides targeting the mutant repeats are ongoing for some HDL types, so enrollment in research studies may be an option.
Diagnosis relies on a combination of clinical assessment and targeted genetic testing. If the patient shows Huntington‑type motor, cognitive, and psychiatric features but testing for the HTT CAG expansion is negative, the physician will order panels that include JPH3 (HDL2), PRNP (HDL1), and TBP (HDL4/SCA17) to identify the specific repeat expansion responsible.
HDL1, HDL2, and HDL4 usually begin in early to mid‑adulthood (30‑50 years) and progress over 10‑20 years with gradual worsening of chorea, dystonia, and dementia. HDL3 is a pediatric form; symptoms start around 3‑4 years of age and advance rapidly, often leading to severe cognitive decline, speech loss, and seizures within the first decade.
ll autosomal‑dominant HDL subtypes (HDL1, HDL2, HDL4) have a 50 % chance of being transmitted to each offspring. HDL2 and HDL4 commonly show anticipation, meaning the repeat length can expand in successive generations, leading to earlier onset and more severe disease in children. Genetic counseling is strongly recommended before family planning.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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