NM_000489.5:c.4434_4435del (p.Lys1479AsnfsTer6) is a frameshift deletion in exon 15 of the ATRX gene, predicted to trigger nonsense-mediated decay and result in complete loss of the C-terminal helicase domain and approximately 1,000 C-terminal amino acids.¹ ATRX loss of function is an established disease mechanism for ATR-X syndrome, an X-linked disorder characterized by developmental delay, facial dysmorphism, genital abnormalities, and alpha thalassemia.² The helicase/ATPase domain (aa ~1205-1863) is a critical functional domain in ATRX, harboring approximately 30% of all disease-associated missense mutations. This frameshift removes the entire helicase domain.³ The variant is absent from all gnomAD populations (v2.1, v4.1, Canada), consistent with rarity in the general population.⁴ No functional studies, clinical observations, segregation data, or variant-specific publications were identified for this specific variant. Five publications retrieved via OncoKB were reviewed in full text; none mention NM_000489.5:c.4434_4435del. These papers address general ATRX biology including the ADD domain structure, R37X translational rescue, mutation spectrum, and ALT phenotype in PanNETs.⁵