Spastic Paralysis, Infantile-Onset Ascending

A number sign (#) is used with this entry because a subset of infantile-onset ascending hereditary spastic paralysis (IAHSP) is caused by homozygous mutation in the alsin gene (ALS2; 606352) on chromosome 2q33.

Mutations in the same gene cause juvenile amyotrophic lateral sclerosis (205100) or juvenile primary lateral sclerosis (606353).

Description

Infantile-onset ascending spastic paralysis is an autosomal recessive neurodegenerative disorder characterized by onset in the first years of life of progressive upper and lower motor neuron degeneration resulting in loss of ability to walk in childhood. It initially affects the lower limbs and then ascends to the upper limbs and bulbar muscles, causing dysarthria and dysphagia. Cognition is unaffected (summary by Wakil et al., 2014).

Clinical Features

Eymard-Pierre et al. (2002) studied 15 patients from 10 families who presented with severe spastic paralysis with an infantile onset and an ascending progression. Spastic paraplegia began during the first 2 years of life and extended to upper limbs within the next few years. During the first decade of life, the disease progressed to tetraplegia, anarthria, dysphagia, and slow eye movements. Overall, however, the disease was compatible with long survival. Signs of lower motor neuron involvement were never observed, whereas motor-evoked potentials and magnetic resonance imaging demonstrated a primitive, pure degeneration of the upper motor neurons.

Lesca et al. (2003) provided further clinical information on the 10 families reported by Eymard-Pierre et al. (2002) and 1 additional family. All patients had normal intellectual function. Many patients became wheelchair-bound in the second decade, and in 1 family, affected members never achieved walking or running. All patients developed upper limb and bulbar involvement. Motor evoked potentials demonstrated a severe dysfunction of the corticospinal tracts. Brain MRI was normal in young patients. MRI in the oldest patients showed brain cortical atrophy, predominantly in the motor areas, and T2-weighted bilateral hyperintense signals in the posterior arms of the internal capsule and brainstem. EMG and muscle biopsies were normal in all patients, excluding involvement of the lower motor neurons.

Gros-Louis et al. (2003) reported a large consanguineous Pakistani family with infantile-onset complicated spastic paraparesis. The proband presented with gait disturbance and hyperreflexia at 18 months and was anarthric and wheelchair-bound by age 12 years. Family history indicated that the disease slowly progressed to tetraplegia and death by the fourth decade, with relatively preserved intellect.

Sztriha et al. (2008) reported 2 sisters with IAHSP resulting from compound heterozygous truncating mutations in the ALS2 gene. Both had a severe form of the disorder with early onset, inability to walk, and bulbar palsy with drooling, dysphagia, and dysarthria. Both became wheelchair-bound in the first decade of life. Intellect was normal. The authors noted that the absence of consanguinity in a family should not excluded a diagnosis of IAHSP.

Wakil et al. (2014) reported 2 sibs, born of consanguineous Saudi parents, with IAHSP. After normal early development, both patients developed progressive spastic paraplegia around the age of walking and became wheelchair-bound in mid-childhood. Other features included spastic anarthria and swallowing difficulties; cognition was normal.

Mapping

Genotyping and linkage analyses by Eymard-Pierre et al. (2002) demonstrated that infantile-onset ascending hereditary spastic paralysis is allelic to the condition previously reported as juvenile amyotrophic lateral sclerosis at the ALS2 locus on 2q33-q35 (205100).

Molecular Genetics

Eymard-Pierre et al. (2002) performed mutation analysis on 15 patients with IAHSP from 10 unrelated families of different ethnic origins. They demonstrated truncation mutations in the ALS2 gene in 4 of the 10 families (606352.0005-606352.0008). Mutations in regulatory ALS2 regions or genetic heterogeneity was suspected as the explanation for the failure to find ALS2 mutation in the other 6 families. The discovery of these alsin mutations responsible for a primitive, retrograde degeneration of the upper motor neurons of the pyramidal tracts revealed a clinical continuum from infantile (IAHSP) to juvenile forms with (ALS2) or without (juvenile-onset primary lateral sclerosis; JPLS) lower motor neuron involvement.

In a large Pakistani family with IAHSP, Gros-Louis et al. (2003) identified a 1-bp deletion in the ALS2 gene (606352.0009) that segregated with the disease.

In 2 affected sisters with IAHSP, born of consanguineous Turkish parents, Eymard-Pierre et al. (2006) identified a homozygous missense mutation in the ALS2 gene (606352.0012).

In 2 Dutch sibs, born of consanguineous parents, with IAHSP Verschuuren-Bemelmans et al. (2008) identified a homozygous mutation in the ALS2 gene (Q715X; 606352.0014). The unaffected parents were each heterozygous for the mutation. The phenotype was severe, including lack of bladder or bowel control. The parents were descended from a common ancestor who lived during the 18th century in the province of Friesland, in the northern part of the Netherlands.

Herzfeld et al. (2009) reported a German patient with IAHSP associated with a homozygous splice site mutation in the ALS2 gene that was found to result from maternal uniparental disomy with partial isodisomy of chromosome 2q31-q37 that carried the ALS2 mutation. The findings could be explained by at least 4 recombination events during maternal meiosis, followed by a meiosis I error and postzygotic trisomy rescue or gamete complementation.

In 2 sibs, born of consanguineous Saudi parents, with IAHSP, Wakil et al. (2014) identified a homozygous nonsense mutation in the ALS2 gene (R921X; 606352.0015). The mutation, which was found by homozygosity mapping and candidate gene sequencing, segregated with the disorder in the family.