Care · ZTTK Syndrome
ZTTK By the Numbers
The data behind ZTTK syndrome — patient counts, genetics, and research progress.
Patient Population
The Numbers That Define Our Mission
~79
Cases in published literature
Individuals described in peer-reviewed publications, per the GeneReviews literature review (2025)
Source: GeneReviews NBK618356 (Sept 2025)
~500
Known patients worldwide
Individuals identified through the Foundation's natural-history and registry data — the figure cited by GeneReviews (2025)
Source: Foundation natural-history data (May 2025), as cited in GeneReviews
~1,200
EstimateEstimated new cases per year
Annual birth incidence estimate repeated across the site — no published source confirmed
No published source found (GeneReviews, OMIM #617140, literature review) — flagged for operator review
~2%
Cleft palate prevalence
Percentage of ZTTK patients with cleft palate — among the less common features but clinically significant
Source: Dingemans et al. 2022
21q22
Chromosomal location
The SON gene sits on chromosome 21, long arm, band 22.11 — spanning 34,463 base pairs
Source: NCBI Gene — SON gene locus
12
Exons in the SON gene
The canonical SON transcript encodes a 2,426 amino-acid protein expressed in all human tissues
Source: Kim et al. 2016
Figures marked “Estimate” are being re-verified as the Foundation’s registry and natural-history data grow.
Context
Why the Numbers Are Uncertain
ZTTK syndrome is classified as an ultra-rare disease. The true prevalence is difficult to know because many patients remain undiagnosed — either because whole-exome sequencing has not been performed, or because their variant was not identified as pathogenic at the time of testing.
As genetic testing becomes more widespread and bioinformatics tools improve, the identified population grows. The Foundation maintains a global contact registry and partners with Citizen Health and Rare-X to build the most comprehensive patient dataset possible.
Every identified patient matters. With fewer than 1,000 known cases globally, each family that registers expands the data available to researchers — accelerating the path to treatments.
Progress
Research Milestones
2015
Pathogenic SON mutations first identified as the cause of ZTTK syndrome
2019
Haploinsufficient ZTTK mouse model developed (Ahn lab, UAB)
2022
Largest patient cohort published — 52 individuals (Dingemans et al.)
2023
World-first ZTTK iPSC cell models initiated with isogenic controls
2024
First SON mouse-model paper published (JCI Insight) — ELISA assay development begins
2025
Inaugural Global Conference — 180+ attendees across 2 days
2025
ZTTK enters GeneReviews, the standard clinical reference — citing the Foundation registry: 450–500 known patients worldwide
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Help grow the patient dataset — every registration improves research.
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