Salt and pepper developmental regression syndrome, also known as Amish infantile epilepsy syndrome, is an autosomal recessive neurocutaneous disorder characterized by infantile onset of refractory and recurrent seizures associated with profoundly delayed psychomotor development and/or developmental regression as well as abnormal movements and visual loss (summary by Fragaki et al., 2013). Affected individuals develop hypo- or hyperpigmented skin macules on the trunk, face, and extremities in early childhood (summary by Boccuto et al., 2014). Not all patients have overt seizures (Lee et al., 2016).

A form of axonal Charcot-Marie-Tooth disease, a peripheral sensorimotor neuropathy with symmetric weakness primarily occurring in the lower limbs and reaching the arms only after 5 to 10 years, occasional and predominantly distal sensory loss and reduced tendon reflexes. Presents with gait anomaly between the first and sixth decade and early onset is generally associated to a more severe phenotype that may include foot drop.

Autosomal recessive spinocerebellar ataxia-15 (SCAR15) is characterized by early-onset ataxia, cognitive impairment, dysarthria, and developmental delay. Variable features include seizures, nystagmus, and abnormal reflexes (Seidahmed et al., 2020).

Mitchell syndrome (MITCH) is a progressive disorder characterized by episodic demyelination, sensorimotor polyneuropathy, and hearing loss (Chung et al., 2020).