How is the diagnosis of infantile‑onset ascending hereditary spastic paralysis confirmed?

Diagnosis relies on a combination of clinical pattern (progressive spasticity that ascends from legs to arms and neck), neuroimaging that excludes structural lesions, and molecular testing. Targeted next‑generation sequencing panels for hereditary spastic paraplegia genes (e.g., SPG7, KIF1A, CAPN1) identify pathogenic variants in most cases.

At what age should I become concerned and seek a neurological work‑up if my child shows leg stiffness and exaggerated reflexes?

Early signs typically appear before 24 months. If a toddler has persistent hyperreflexia, frequent leg spasms, or difficulty walking that does not resolve, a prompt evaluation by a pediatric neurologist is recommended to rule out hereditary spastic paraplegia.

What therapies are available to slow the progression of spasticity and preserve function?

There is no disease‑modifying cure, but multidisciplinary management helps. Oral antispasticity agents (baclofen, tizanidine, gabapentin) reduce tone; regular physiotherapy and stretching maintain range of motion; orthotic devices support ambulation; and, when speech or swallowing become affected, speech‑language therapy is introduced. Experimental gene‑therapy approaches are under investigation for specific genetic subtypes.

What long‑term functional outlook can families expect regarding mobility and speech?

The disorder is progressive; many children eventually require a wheelchair in adolescence or early adulthood. Upper‑limb involvement can limit fine motor tasks, and neck‑head muscle weakness may lead to dysarthria and dysphagia in the teenage years. Early and continuous supportive care can maximize independence and quality of life, but complete preservation of ambulation or speech is uncommon.

Infantile-onset ascending hereditary spastic paralysis

Infantile-onset ascending hereditary spastic paralysis is a rare autosomal recessive disorder that begins with leg spasticity in early childhood and progressively involves the arms, neck, and head.

Overview

Infantile-onset ascending hereditary spastic paralysis is one of a group of genetic disorders known as hereditary spastic paraplegias. These disorders are characterized by progressive muscle stiffness (spasticity) and eventual paralysis of the lower limbs (paraplegia). The spasticity and paraplegia result from degeneration (atrophy) of motor neurons, which are specialized nerve cells in the brain and spinal cord that control muscle movement.

Hereditary spastic paraplegias are divided into two types: pure and complicated. The pure types involve only the lower limbs, while the complicated types involve additional areas of the nervous system, affecting the upper limbs and other areas of the body. Infantile-onset ascending hereditary spastic paralysis starts as a pure hereditary spastic paraplegia, with spasticity and weakness in the legs only, but as the disorder progresses, the muscles in the arms, neck, and head become involved and features of the disorder are more characteristic of the complicated type.

Symptoms

Infants are typically normal at birth. Within the first 2 years of life, early symptoms appear, including exaggerated reflexes (hyperreflexia) and recurrent muscle spasms in the legs. As the condition progresses, affected children develop abnormal tightness and stiffness in the leg muscles and weakness in the legs and arms. Over time, muscle weakness and stiffness travel up (ascend) the body from the legs to the head and neck.

Muscles in the head and neck usually weaken during adolescence; symptoms include slow eye movements and difficulty with speech and swallowing. Affected individuals may lose the ability to speak (anarthria). The leg and arm muscle weakness can become so severe as to lead to paralysis; as a result affected individuals require wheelchair assistance by late childhood or early adolescence. Intelligence is not affected in this condition.

Frequency

Infantile-onset ascending hereditary spastic paralysis is a rare disorder, with at least 30 cases reported in the scientific literature.

Causes & Risk Factors

Infantile-onset ascending hereditary spastic paralysis is caused by mutations in the ALS2 gene. This gene provides instructions for making the alsin protein. Alsin is produced in a wide range of tissues, with highest amounts in the brain, particularly in motor neurons. Alsin turns on (activates) multiple proteins called GTPases that convert a molecule called GTP into another molecule called GDP. GTPases play important roles in several cell processes. The GTPases that are activated by alsin are involved in the proper placement of the various proteins and fats that make up the cell membrane, the transport of molecules from the cell membrane to the interior of the cell (endocytosis), and the development of specialized structures that project from neurons and are essential for the transmission of signals.

Mutations in the ALS2 gene alter the instructions for making alsin, often resulting in the production of an abnormally short alsin protein that is unstable and rapidly broken down. It is unclear exactly how ALS2 gene mutations cause infantile-onset ascending hereditary spastic paralysis. Research suggests that a lack of alsin and the subsequent loss of GTPase functions, such as endocytosis and the development of axons and dendrites, contribute to the progressive atrophy of motor neurons that is characteristic of this condition.

Learn more about the gene associated with Infantile-onset ascending hereditary spastic paralysis

ALS2

Inheritance

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Other Names

IAHSP
Infantile onset ascending spastic paralysis
Infantile-onset ascending hereditary spastic paraplegia

Additional Information & Resources

Genetic Testing Information

Genetic Testing Registry: Hereditary spastic paraplegia
Genetic Testing Registry: Infantile-onset ascending hereditary spastic paralysis

Genetic and Rare Diseases Information Center

Hereditary spastic paraplegia
Infantile-onset ascending hereditary spastic paralysis

Patient Support and Advocacy Resources

National Organization for Rare Disorders (NORD)

Clinical Trials

ClinicalTrials.gov

Catalog of Genes and Diseases from OMIM

SPASTIC PARALYSIS, INFANTILE-ONSET ASCENDING; IAHSP

Scientific Articles on PubMed

PubMed

References

Eker HK, Unlu SE, Al‑Salmi F, Crosby AH. A novel homozygous mutation in ALS2 gene in four siblings with infantile‑onset ascending hereditary spastic paralysis. Eur J Med Genet. 2014 May‑Jun;57(6):275‑8. doi:10.1016/j.ejmg.2014.03.006. Epub 2014 Apr 3.
Lesca G, Eymard‑Pierre E, Santorelli FM, et al. Infantile ascending hereditary spastic paralysis (IAHSP): clinical features in 11 families. Neurology. 2003 Feb 25;60(4):674‑82. doi:10.1212/01.wnl.0000048207.28790.25.
Orrell RW. ALS2‑Related Disorder. 2005 Oct 21 [updated 2021 May 13]. In: Adam MP, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993‑2026. Available from http://www.ncbi.nlm.nih.gov/books/NBK1243/
Racis L, Tessa A, Pugliatti M, et al. Infantile‑onset ascending hereditary spastic paralysis: a case report and brief literature review. Eur J Paediatr Neurol. 2014 Mar;18(2):235‑9. doi:10.1016/j.ejpn.2013.09.009. Epub 2013 Oct 9.
Wakil SM, Ramzan K, Abuthuraya R, et al. Infantile‑onset ascending hereditary spastic paraplegia with bulbar involvement due to the novel ALS2 mutation c.2761C>T. Gene. 2014 Feb 15;536(1):217‑20. doi:10.1016/j.gene.2013.11.043. Epub 2013 Dec 4.