Clinical Manifestations and Outcomes of 20 Korean Hypochondroplasia Patients with the FGFR3 N540K variant

BACKGROUND: N540K variant. METHODS: , or target-panel sequencing for skeletal dysplasia. The effectiveness of growth hormone therapy was analyzed in 16 patients treated with growth hormones. RESULTS: Among 20 patients (7 men, 13 women), the mean age at first visit was 3.5±1.0 years, and the mean follow-up duration was 6.8±0.6 years. The patients presented with a short stature and/or short limbs. Genu varum, macrocephaly, and developmental delay were observed in 11 (55.0%), 9 (45.0%), and 5 (25.0%) patients, respectively. Of the 12 patients who underwent neuroimaging, five (41.7%) showed abnormal findings (one required operation for obstructive hydrocephalus). Among 16 growth-hormone-treated patients (two were growth-hormone deficient), the increase in height standard deviation scores was significant after a mean 5.4±0.7 years of treatment (+0.6 and+1.8 using growth references for healthy controls and achondroplasia children, respectively). Four patients underwent surgical limb lengthening at a mean age of 8.8±3.3 years. CONCLUSIONS: Neurodevelopmental abnormalities are frequently observed in patients with N540K-related hypochondroplasia. Close monitoring of skeletal manifestations and neurodevelopmental status is necessary for hypochondroplasia.