Early hypotonia, narrow chest, tongue fasciculations, hypo- or areflexia 
– consider spinal muscle atrophy (SMA type 1); autosomal recessive mutation in the Survival Motor Neuron (SMN1) gene
– often progresses to respiratory failure and is nearly always fatal by age 2 

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Low levels of beta-glucocerebrosidase => Gaucher disease 
– can present in infants (more severe in “Type 2” Gaucher disease) with hypertonia and organomegaly 

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Mutations in ALS2 gene => infantile-onset ascending hereditary spastic paralysis and juvenile amyotrophic lateral sclerosis (JALS), which are disorders of spasticity, not hypotonia