Huntington Disease-Like 1 (HDL1): A Patient Guide

Huntington disease-like 1 (HDL1) is an exceptionally rare, genetic brain disorder that belongs to a family of conditions known as inherited prion diseases. For many families, the road to this diagnosis is long and exhausting, often beginning with a search for answers regarding involuntary movements, memory changes, or shifts in personality. Because these symptoms so closely resemble those of Huntington’s disease, many patients are initially misdiagnosed or spend years undergoing testing before the true cause—a pathogenic mutation in the PRNP gene—is identified ^[1][2].

While it shares a name and many symptoms with Huntington’s, HDL1 is biologically distinct. It is caused by a genetic instruction present from birth that eventually leads to the misfolding of prion proteins ^[1]. This misfolding gradually impacts the brain’s ability to control movement and thinking. Unlike some other rapidly fatal prion diseases that progress in a matter of weeks, the course of HDL1 is famously variable. In some individuals, the disease may move quickly over months, while in others, it progresses slowly over several decades, closely mimicking the timeline of more common neurodegenerative conditions ^[3][1].

Because HDL1 is inherited in an autosomal dominant pattern, each child of a parent carrying one copy of the pathogenic mutation has a 50% chance of inheriting it. This makes professional genetic counseling a cornerstone of care for the entire family. These conversations help relatives understand their risks, navigate the emotional weight of testing, and explore options for family planning in a supportive, informed environment ^[4][5].

Currently, there is no cure for HDL1, but there is a great deal that can be done to support those living with it. Care is centered on a multidisciplinary approach, bringing together movement-disorder neurologists, physical and occupational therapists, speech-language pathologists, and mental health professionals. The primary goal of treatment is to address specific symptoms as they arise—sometimes utilizing medications off-label—ensuring the highest possible quality of life and providing the family with the tools they need to navigate the journey ahead with clarity and dignity ^[6][1].

Note: While HDL1 is a prion disease, it is genetic, not contagious through casual contact. Standard infection-control precautions are used in healthcare, but you should always inform your medical team of your diagnosis before any invasive procedures or surgeries.