[citation needed] The first features of the syndrome start off with feeding difficulties, constant irritability, frequent vomiting, and hypotonia.

[14] These mutations are inherited in an autosomal recessive fashion, which means that for a child to show the signs of the disorder, both of their parents must have transmitted them at least one copy of the dysfunctional ST3GAL5 gene.

[citation needed] Jamal et al. (2021) found a homozygous frameshift mutation (c.1030_1031del) in the ST3GAL5 gene of an Iranian child with the disorder born to consanguineous, first-cousin parents.

[22] Electroencephalograms done on the affected patients reported by Simpson et al. showed "multifocal epileptiform discharges" which were "superimposed on a diffuse slow background activity.

[citation needed] In 2006, Fahhad et al. published the results of an ophthalmoscopy study done on 4 children from 2 sibships of an Amish family; they showed optic nerve paleness on both eyes, indicative of bilateral optic atrophy, a condition which can lead to visual impairment and is usually associated with other disorders (including salt pepper syndrome).

[citation needed] Jamal et al. (2021) found microcephaly on a child with the disorder prior to her birth using this diagnostic method.

[citation needed] A study done in 2019 by Bowser et al. on 50 Amish patients with the condition showed that prescribed antiseizure medications such as phenobarbital, benzodiazepines, and valproic acid had some effect at treating the patients' seizures, insomnia, and irritability, which helped decrease their parents' overall stress of taking care of them.

[28] This condition was first discovered in 2004 by Simpson et al. Their patients were 9 members from 2 sibships belonging to a single large, endogamous Amish family from Geauga County, Ohio.

Their symptoms started between the ages of 2 weeks old and 3 months old, with irritability, vomiting, feeding difficulties and a failure to thrive followed by seizures in the first year of their life.

[23] Although salt and pepper developmental regression syndrome is prevalent among the Old Order Amish, further studies in 2016, 2021, and in 2023, found it in two Korean sisters, in an Iranian patient, and in a family in Saudi Arabia.