Overview
Autosomal recessive spastic paraplegia type 66 (SPG66) is an extremely rare inherited neurological condition that primarily affects the nervous system, leading to progressive stiffness and weakness in the legs. It belongs to a large group of disorders known as hereditary spastic paraplegias (HSPs), which share the hallmark feature of gradually increasing muscle tightness (spasticity) in the lower limbs. SPG66 is caused by mutations in the ARSI gene, which provides instructions for making an enzyme called arylsulfatase I. When this enzyme does not work properly, nerve cells that control movement are progressively damaged. People with SPG66 typically develop symptoms in early childhood. The most prominent features include difficulty walking due to leg stiffness, intellectual disability, and delayed developmental milestones. Some individuals may also experience seizures, speech difficulties, and problems with fine motor skills. The severity of symptoms can vary between affected individuals, even within the same family. There is currently no cure for SPG66. Treatment focuses on managing symptoms and improving quality of life. Physical therapy, occupational therapy, and medications to reduce muscle spasticity (such as baclofen or tizanidine) are commonly used. Orthopedic interventions, including braces or surgery, may be needed to address joint contractures or skeletal deformities. Because this condition is so rare, research is still ongoing to better understand the disease and develop more targeted therapies.
Also known as:
Key symptoms:
Progressive leg stiffness and spasticityDifficulty walking or inability to walk independentlyIntellectual disabilityDelayed developmental milestonesSpeech and language difficultiesSeizuresPoor coordination and balanceMuscle weakness in the legsJoint contractures (tightening of joints)Abnormal gait patternDifficulty with fine motor skillsFoot deformities such as high arches or turned-in feet
Clinical phenotype terms (14)— hover any for plain English
Autosomal recessive
Passed on when both parents carry the same gene change; often skips generations
Childhood
Begins in childhood, roughly ages 1 to 12
Treatments
No FDA-approved treatments are currently listed for Autosomal recessive spastic paraplegia type 66.
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Specialists
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Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to Autosomal recessive spastic paraplegia type 66.
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Caregiver Resources
NORD Caregiver Resources
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Mental Health Support
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Family & Caregiver Grants
Financial assistance programs specifically for caregivers of rare disease patients.
Social Security Disability
Learn how rare disease patients may qualify for SSDI/SSI benefits.
Questions for your doctor
Bring these to your next appointment
- Q1.What is the expected progression of symptoms in my child's specific case?,What therapies (physical, occupational, speech) should we start right away?,Are there any medications that can help with the leg stiffness, and what are the side effects?,Should we be monitoring for seizures, and what should we do if one occurs?,Are there any clinical trials or research studies we could participate in?,What genetic counseling is available for our family regarding future pregnancies?,What educational and social support services should we look into for our child?
Common questions about Autosomal recessive spastic paraplegia type 66
What is Autosomal recessive spastic paraplegia type 66?
Autosomal recessive spastic paraplegia type 66 (SPG66) is an extremely rare inherited neurological condition that primarily affects the nervous system, leading to progressive stiffness and weakness in the legs. It belongs to a large group of disorders known as hereditary spastic paraplegias (HSPs), which share the hallmark feature of gradually increasing muscle tightness (spasticity) in the lower limbs. SPG66 is caused by mutations in the ARSI gene, which provides instructions for making an enzyme called arylsulfatase I. When this enzyme does not work properly, nerve cells that control movemen
How is Autosomal recessive spastic paraplegia type 66 inherited?
Autosomal recessive spastic paraplegia type 66 follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Autosomal recessive spastic paraplegia type 66 typically begin?
Typical onset of Autosomal recessive spastic paraplegia type 66 is childhood. Age of onset can vary across affected individuals.