Skeletal dysplasias — branching viva

Opening branch — the disproportionate child

A two-year-old has rhizomelic shortening, a large head with frontal bossing and midface hypoplasia, trident hands, and genu varum, with normal development. The candidate must give the diagnosis of achondroplasia, name the FGFR3 gain-of-function mechanism that brakes chondrocyte proliferation at the growth plate, and explain why around eighty per cent of cases arise as new variants in average-statured parents. The investigation is a skeletal survey and molecular confirmation of the recurrent FGFR3 variant, and the management is syndrome-specific surveillance plus the consideration of vosoritide. ^{[1] [2]}

The examiner probes the surveillance. The candidate names the foramen magnum stenosis and sleep-disordered breathing that threaten the achondroplastic infant, the recurrent otitis media and conductive hearing loss, the risk of hydrocephalus, and the need for syndrome-specific growth charts. The teaching point is that the complications of achondroplasia are life-threatening even when the child looks well, so structured surveillance rather than reassurance is the standard of care. ^{[1] [2]}