Table 1 The genetic mutations, protein products, clinical features, and general intellectual functioning associated with TS, NS and NF1

Turner syndrome

X chromosome partial (mosaic)/complete deletion

Reduced expression of gene products encoded by X-linked genes escaping X-inactivation [121]

Renal/endocrine problems, cardiac defects, short stature, webbed neck, eyelid ptosis, increased inter-nipple distance [114, 116]

Mosaic/partial X chromosome absence:

VIQ: 96.2 ± 15.9

PIQ: 79.5 ± 18.8

Complete X chromosome absence:

VIQ: 106.4 ± 14.4

PIQ: 82.1 ± 15.9

[48]

Noonan syndrome

- PTPN11 (50%) ⇒

⇑ Shp2 tyrosine phosphate enzyme

Short stature, webbed neck, eyelid ptosis, increased inter-nipple distance, cardiac defects, bleeding disorders [114, 115, 117, 118]

VIQ: 82.3 ± 20.0

PIQ: 87.1 ± 23.0

(May vary depending upon specific mutation [119, 120])

- SOS1 (10–15%) ⇒

⇑ “Son Of Sevenless 1” protein

- RAF1 (5–10%) ⇒

⇑ Serine-threonine kinase activating MEK1/MEK2

- KRAS (0–5%) ⇒

[111]

Missense mutation KRAS Isoform B [118]

- Other rare mutations

Neurofibromatosis type 1

NF1 gene microdeletion (chromosome 17q11) [112]

⇓ Neurofibromin [113]

Café-au-lait spots, intertriginous freckling, Lisch nodules, neurofibromas, optic pathway gliomas, distinctive bony lesions [111-113]

VIQ: 91.9 ± 14.7

PIQ: 91.1 ± 12.8

[11]