| TTI2 variant | Amino acid changes | Zygosity | Phenotype | Reported cases | Publication year | References |
| c.21_22insAAGCGCTCTG | p.Glu8Lysfs × 12 | Homozygous | Intellectual disability, microcephaly, delayed psychomotor development, speech delay, short stature, dysmorphic facial features, esotropia, kyphoscoliosis, and behavior abnormalities | 1 | Reported here | Reported here |
| c.950A > T | p.Asp317Val | Homozygous | Primary microcephaly, short stature, severe speech delay, dysmorphic features, strabismus, and dyskinesia | 1 | 2020 | [19] |
| Patient 1 c.1075C > T and c.950A > T | p.Arg359Cys and p.Asp317Val | Compound heterozygous | Intellectual disabilities, progressive microcephaly, high nasal bridge, deep-set eyes, and partial ovarian failure | 2 | 2019 | [20] | Patient 2 c.539T > C and c.575T > C | p.Leu180Pro and p.Leu192Pro | Compound heterozygous |
| c.942_944delTCTins and c.1100C > T | p.Leu315CysfsTer8 and p.Pro367Leu | Compound heterozygous | Intellectual disabilities, microcephaly, growth retardation, speech disorder, and movement disorders | 2 | 2019 | [9] |
| c.1307T > A | p.Ile436Asn | Homozygous | Normal growth parameters, microcephaly at adult age, severe cognitive impairment, severe speech delay, short stature, dysmorphic features, and vertebral anomalies | 3 | 2013 | [5] |
| c.1100C > T | p.Pro367Leu | Homozygous | Non-syndromic moderate intellectual disability | 2 | 2011 | [4] |
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