New Magnetic Resonance Imaging (MRI) findings in a patient with hypochondroplasia caused by the FGFR3 N540K variant

Novos achados de ressonância magnética (RM) em um paciente com hipocondroplasia causada pela variante FGFR3 N540K

A 7-year-old boy with hypochondroplasia had neurodevelopmental delay, mild cognitive impairment, subtle motor deficits and without epilepsy. There was no obstetric problem or perinatal impairment. Genetic revealed the p.N540K FGFR3 variant. MRI findings are depicted (Figure 1).

Figure 1.
(A) Axial FLAIR-weighted image shows posterior periventricular white-matter hyperintensities. (B) Axial Apparent diffusion coefficient (ADC) map showing hyperintensities in the periventricular white-matter (reflecting absence of restricted diffusion). (C) Axial T2-weighted image shows posterior periventricular white-matter hyperintensities. (D) Axial and (E) Coronal T1-weighted image after gadolinium contrast, demonstrating absence of enhancement. (F) Coronal T2-weighted image without evidence of hippocampal abnormalities.

FGFR3 regulates chondrocyte proliferation and differentiation and is instrumental in cortical patterning and neurogenesis¹. Temporal lobe dysgenesis is common in FGFR3-related hypochondroplasia^2,3. Squared and enlarged lateral ventricles, with reduced peritrigonal white matter (WM) have been described², but periventricular WM hyperintensities on T2/FLAIR weighted images, as demonstrated here, were not reported previously.

Such WM lesions expand the neuroimaging signature in FGFR3-related hypochondroplasia.

References

• 1. Hevner RF. The cerebral cortex malformation in thanatophoric dysplasia: neuropathology and pathogenesis. Acta Neuropathol. 2005 Sep;110(3):208-21.
• 2. Linnankivi T, Mäkitie O, Valanne L, Toiviainen-Salo S. Neuroimaging and neurological findings in patients with hypochondroplasia and FGFR3 N540K mutation. Am J Med Genet A. 2012;158A(12):3119-25. https://doi.org/10.1002/ajmg.a.35642
  » https://doi.org/10.1002/ajmg.a.35642
• 3. Philpott CM, Widjaja E, Raybaud C, Branson HM, Kannu P, Blaser S. Temporal and occipital lobe features in children with hypochondroplasia/FGFR3 gene mutation. Pediatr Radiol. 2013 Sep;43(9):1190-5. https://doi.org/ 10.1007/s00247-013-2684-3
  » https://doi.org/ 10.1007/s00247-013-2684-3

Publication Dates

• Publication in this collection
  11 June 2021
• Date of issue
  July 2021

History

• Received
  09 Sept 2020
• Reviewed
  27 Sept 2020
• Accepted
  07 Oct 2020