Genetic and Phenotypic Features of the Five Known Polyaminopathies: A Critical Narrative Review

Polyaminopathies are a recently described family of rare genetic neurodevelopmental disorders. Polyaminopathies disrupt the biosynthesis of the primary polyamines: putrescine, spermidine, and spermine. Snyder–Robinson syndrome results from hemizygous loss‐of‐function variants in the spermine synthase ( SMS ) gene, resulting in decreased or complete loss of spermine synthase enzyme activity. Bachmann–Bupp syndrome results from heterozygous gain‐of‐function variants in the ornithine decarboxylase 1 ( ODC1 ) gene, resulting in increased ornithine decarboxylase enzyme activity. Faundes–Banka syndrome results from heterozygous loss‐of‐function variants in the eukaryotic translation initiation factor 5A ( EIF5A ) gene, impairing eIF5A protein function. DHPS (deoxyhypusine synthase) deficiency is an autosomal recessive disease and results from bi‐allelic hypomorphic variants in the deoxyhypusine synthase ( DHPS ) gene, which results in reduced deoxyhypusine synthase enzyme activity. Finally, DOHH (deoxyhypusine hydroxylase) disorder is an autosomal recessive disorder caused by bi‐allelic loss‐of‐function variants in the deoxyhypusine hydroxylase ( DOHH ) gene, which causes decreased deoxyhypusine hydroxylase enzyme activity. Snyder–Robinson syndrome was first described in 1969, while the other four syndromes have only been identified in the past 7 years. A comprehensive phenotypic and genotypic description of these five syndromes is needed. We review the clinical and genetic features of these five polyaminopathies to create an inclusive clinical resource. A systematic keyword search strategy was used to identify all published cases in PubMed, Web of Science, and Scopus databases. The five known syndromes associated with the polyamine pathway share many similar clinical phenotypes, and yet patients with each syndrome present with distinctive syndromic features. This review will serve as a valuable resource for clinicians diagnosing and caring for patients with these rare polyaminopathies.