Table 1.

Comparison of the main clinical features characterizing ALS2 gene mutation-related diseases, i.e., IAHSP, JPLS, and JALS.

	IAHSP	JPLS	JALS
Inheritance	Autosomal recessive	Autosomal recessive	Autosomal recessive
Age of onset	1–3 years old	1–3 years old	4–8 years old
Life expectancy	Adulthood	Adulthood	7 months to 17 years old
Genetic causes	ALS2 mutation	ALS2 mutation	ALS2 mutation (Other forms are caused by SETX, FUS, UBQLN2, SPG11, SIGMAR1)
Neuron alterations	Degeneration of both upper and lower motor neurons	Progressive degeneration, upper motor neurons	Degeneration of both upper and lower motor neurons
Symptoms	Lower limb weakness and spasticity progressing towards quadriplegia, wheelchair dependence by the age of 10, followed by tetraparesis, feeding dependence on gastrostomy	Lower limb weakness and spasticity, wheelchair dependence by adolescence, motor speech impairment, saccadic eye movements	Lower limb weakness and spasticity, face muscle spasticity, bladder dysfunction, dysarthria, sensory disturbances, and sometimes mental retardation and sclerosis