Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease (MJD), is characterized by progressive cerebellar ataxia and variable findings including pyramidal signs, a dystonic-rigid extrapyramidal syndrome, significant peripheral amyotrophy and generalized areflexia, progressive external ophthalmoplegia, action-induced facial and lingual fasciculations, and bulging eyes. Neurologic findings tend to evolve as the disorder progresses.

X-linked adrenoleukodystrophy (X-ALD) affects the nervous system white matter and the adrenal cortex. Three main phenotypes are seen in affected males: The childhood cerebral form manifests most commonly between ages four and eight years. It initially resembles attention-deficit disorder or hyperactivity; progressive impairment of cognition, behavior, vision, hearing, and motor function follow the initial symptoms and often lead to total disability within six months to two years. Most individuals have impaired adrenocortical function at the time that neurologic disturbances are first noted. Adrenomyeloneuropathy (AMN) manifests most commonly in an individual in his twenties or middle age as progressive stiffness and weakness of the legs, sphincter disturbances, sexual dysfunction, and often, impaired adrenocortical function; all symptoms are progressive over decades. "Addison disease only" presents with primary adrenocortical insufficiency between age two years and adulthood and most commonly by age 7.5 years, without evidence of neurologic abnormality; however, some degree of neurologic disability (most commonly AMN) usually develops by middle age. More than 20% of female carriers develop mild-to-moderate spastic paraparesis in middle age or later. Adrenal function is usually normal.

Spinocerebellar ataxia type 1 (SCA1) is characterized by progressive cerebellar ataxia, dysarthria, and eventual deterioration of bulbar functions. Early in the disease, affected individuals may have gait disturbance, slurred speech, difficulty with balance, brisk deep tendon reflexes, hypermetric saccades, nystagmus, and mild dysphagia. Later signs include slowing of saccadic velocity, development of up-gaze palsy, dysmetria, dysdiadochokinesia, and hypotonia. In advanced stages, muscle atrophy, decreased deep tendon reflexes, loss of proprioception, cognitive impairment (e.g., frontal executive dysfunction, impaired verbal memory), chorea, dystonia, and bulbar dysfunction are seen. Onset is typically in the third or fourth decade, although childhood onset and late-adult onset have been reported. Those with onset after age 60 years may manifest a pure cerebellar phenotype. Interval from onset to death varies from ten to 30 years; individuals with juvenile onset show more rapid progression and more severe disease. Anticipation is observed. An axonal sensory neuropathy detected by electrophysiologic testing is common; brain imaging typically shows cerebellar and brain stem atrophy.

Spinocerebellar ataxia type 2 (SCA2) is characterized by progressive cerebellar ataxia, including nystagmus, slow saccadic eye movements, and in some individuals, ophthalmoparesis or parkinsonism. Pyramidal findings are present; deep tendon reflexes are brisk early on and absent later in the course. Age of onset is typically in the fourth decade with a ten- to 15-year disease duration.

A form of hereditary spastic paraplegia which usually presents in late adolescence or early adulthood as a pure phenotype of lower limb spasticity with hyperreflexia and extensor plantar responses, as well as mild bladder disturbances and pes cavus. Rarely, it can present as a complex phenotype with additional manifestations including epilepsy, variable peripheral neuropathy and/or memory impairment. Caused by mutations in the NIPA1 gene (15q11.2) encoding the magnesium transporter NIPA1.

Spastic paraplegias (SPGs) are a genetically heterogeneous group of neurologic disorders characterized by progressive weakness and spasticity of the legs. Complicated SPGs are accompanied by additional neurologic symptoms such as cerebellar ataxia, sensory loss, mental retardation, nystagmus, and optic atrophy (summary by Steinmuller et al., 1997). A locus for spastic paraplegia-16 has been mapped to Xq11.2-q23 (Steinmuller et al., 1997). For a discussion of genetic heterogeneity of X-linked spastic paraplegia, see 303350.

Spastic paraplegia 7 (SPG7) is characterized by insidiously progressive bilateral leg weakness and spasticity. Most affected individuals have decreased vibration sense and cerebellar signs. Onset is mostly in adulthood, although symptoms may start as early as age 11 years and as late as age 72 years. Additional features including ataxia (gait and limbs), spastic dysarthria, dysphagia, pale optic disks, ataxia, nystagmus, strabismus, ptosis, hearing loss, motor and sensory neuropathy, amyotrophy, scoliosis, pes cavus, and urinary sphincter disturbances may be observed.

A pure form of hereditary spastic paraplegia with characteristics of a slowly progressive and relatively benign spastic paraplegia presenting in adulthood with spastic gait, lower limb hyperreflexia, extensor plantar responses, bladder dysfunction (urinary urgency and/or incontinence), and mild sensory and motor peripheral neuropathy.

Spastic paraplegia 15 (SPG15), typically an early-onset complex hereditary spastic paraplegia, is characterized by progressive spasticity that begins in the lower extremities and is associated with several manifestations resulting from central and peripheral nervous system dysfunction. While onset of spasticity is typically in mid- to late childhood or adolescence (i.e., between ages 5 and 18 years), other manifestations, such as developmental delay or learning disability, may be present earlier, often preceding motor involvement. Individuals with adult onset have also been reported.

A rare hereditary spastic paraplegia with characteristics of progressive spastic paraplegia with pyramidal signs in the lower limbs, decreased vibration sense, and increased reflexes in the upper limbs. Caused by heterozygous mutation in the HSPD1 on chromosome 2q33.

Spastic paraplegia-12 is an autosomal dominant neurodegenerative disorder characterized by lower limb spasticity and hyperreflexia, resulting in walking difficulties. Some patients may have urinary symptoms and distal sensory impairment. The age at onset is variable and can range from childhood to adulthood (summary by Montenegro et al., 2012). For a general description and a discussion of genetic heterogeneity of autosomal dominant spastic paraplegia, see SPG3A (182600).

Spastic paraplegia 11 (SPG11) is characterized by progressive spasticity and weakness of the lower limbs frequently associated with the following: mild intellectual disability with learning difficulties in childhood and/or progressive cognitive decline; peripheral neuropathy; pseudobulbar involvement; and increased reflexes in the upper limbs. Less frequent findings include: cerebellar signs (ataxia, nystagmus, saccadic pursuit); retinal degeneration; pes cavus; scoliosis; and parkinsonism with characteristic brain MRI features that include thinning of the corpus callosum. Onset occurs mainly during infancy or adolescence (range: age 1-31 years) and in rare cases as late as age 60 years. Most affected individuals become wheelchair bound one or two decades after disease onset.

Spastic paraplegia-10 (SPG10) is an autosomal dominant neurologic disorder with variable manifestations. Some patients have onset of a 'pure' spastic paraplegia, with lower limb spasticity, hyperreflexia, extensor plantar responses, and variable involvement of the upper limbs beginning in childhood or young adulthood. Some patients show distal sensory impairment, which can be part of the 'pure' phenotype. However, some patients also show an axonal sensorimotor peripheral neuropathy with distal sensory impairment and distal muscle atrophy reminiscent of Charcot-Marie-Tooth disease type 2 (see, e.g., CMT2A, 118210). Rarely, patients with KIF5A mutations may have additional neurologic features, including parkinsonism or cognitive decline, consistent with a 'complicated' phenotype. Spastic paraplegia and peripheral neuropathy in isolation may represent extreme ends of the phenotypic spectrum of KIF5A mutations (summary by Goizet et al., 2009 and Crimella et al., 2012). For a general phenotypic description and a discussion of genetic heterogeneity of autosomal dominant spastic paraplegia, see SPG3A (182600).

Hereditary spastic paraplegia 8 (SPG8) is a slowly progressive pure spastic paraplegia of the lower limbs (i.e., pyramidal signs including hyperreflexia, spasticity, and occasionally clonus without other neurologic findings). Some affected individuals have urinary urgency that usually becomes apparent at the same time as the spasticity. Onset is between ages ten and 59 years. Affected individuals often become wheelchair dependent. While intra- and interfamilial phenotypic variability is high, SPG8 is typically more severe than other types of hereditary spastic paraplegia.

Spastic paraplegia 4 (SPG4; also known as SPAST-HSP) is characterized by insidiously progressive bilateral lower-limb gait spasticity. More than 50% of affected individuals have some weakness in the legs and impaired vibration sense at the ankles. Sphincter disturbances are very common. Onset is insidious, mostly in young adulthood, although symptoms may start as early as age one year and as late as age 76 years. Intrafamilial variation is considerable.

Spastic paraplegia 3A (SPG3A; also known as ATL1-HSP) is characterized by progressive bilateral and mostly symmetric spasticity and weakness of the legs. Compared to other forms of autosomal dominant hereditary spastic paraplegia (HSP), in which diminished vibration sense (caused by degeneration of the corticospinal tracts and dorsal columns) and urinary bladder hyperactivity are present in all affected individuals, these findings occur in a minority of individuals with SPG3A. The average age of onset is four years. More than 80% of reported individuals manifest spastic gait before the end of the first decade of life. Most persons with early-onset ATL1-HSP have a "pure" ("uncomplicated") HSP; however, complicated HSP with axonal motor neuropathy and/or distal amyotrophy with lower motor neuron involvement (Silver syndrome phenotype) has been observed. The rate of progression in ATL1-HSP is slow, and wheelchair dependency or need for a walking aid (cane, walker, or wheelchair) is relatively rare.

Hereditary spastic paraplegia-72A (SPG72A) is a pure form of spastic paraplegia with onset of difficulty walking and stiff legs associated with hyperreflexia and extensor plantar responses in early childhood. The disorder is slowly progressive, and some patients develop the need for assistance in walking. Some patients may have pes cavus or sphincter disturbances. Cognition, speech, and ocular function are normal (summary by Esteves et al., 2014). For a discussion of genetic heterogeneity of autosomal dominant spastic paraplegia, see SPG3A (182600).

Spastic paraplegia-30 (SPG30) is a neurologic disorder characterized by onset of slowly progressive spastic paraplegia in the first or second decades of life. Affected individuals have unsteady spastic gait and hyperreflexia of the lower limbs. Some patients have a 'pure' form of the disorder, limited to spastic paraplegia, whereas others may have a 'complicated' form that includes cognitive dysfunction, learning disabilities, or behavioral abnormalities, peripheral sensorimotor neuropathy, urinary sphincter problems, and/or cerebellar atrophy with thin corpus callosum on brain imaging. The phenotypic features represent a spectrum of abnormalities of the central, peripheral, and autonomic nervous system (summary by Pennings et al., 2020). For a discussion of genetic heterogeneity of autosomal dominant spastic paraplegia, see SPG3A (182600). For a discussion of genetic heterogeneity of autosomal recessive spastic paraplegia, see SPG5A (270800).