Volume 35
(2026)
Issue 4
Pages
337-343
Diagnostic guide to hypochondroplasia
Takuo Kubota, Gen Nishimura, Hiroshi Kitoh, Yasuhisa Ohata, Tsuyoshi Isojima, Keita Okada, Sumito Dateki, Kosei Hasegawa, Ikuma Fujiwara, Masaki Matsushita, Noriyuki Namba, Keiichi Ozono, Toshimi Michigami
Hypochondroplasia is a skeletal dysplasia characterized by disproportional short stature with rhizomelic limb shortening, caused by pathogenic variants of FGFR3, most frequently the p.Asn540Lys variant. However, affected individuals harbor a wide variety of pathogenic variants, accounting for the broad phenotypic spectrum of the disorder. Despite being closely related to achondroplasia, hypochondroplasia is a milder condition that was previously believed to be recognizable only in childhood, but not in infancy. However, the widespread use of prenatal ultrasonography and frequent diagnosis of fetal limb shortening have increased the number of hypochondroplastic neonates identified, thereby clarifying the early radiographic findings of the disorder. Radiological diagnosis of hypochondroplasia in children carrying the p.Asn540Lys variant is currently feasible in the neonatal period or even prenatally, using three-dimensional CT. Conversely, some individuals have a mild phenotype with minimal skeletal abnormalities, which hampers the differential diagnosis of hypochondroplasia and constitutional short stature. For a definitive diagnosis, genetic testing for FGFR3 is recommended. This diagnostic guide aims to assist in the early recognition of hypochondroplasia and to facilitate the management of affected children.
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Editor's pick
Hypochondroplasia is a fibroblast growth factor
receptor 3 (FGFR3)-related skeletal dysplasia with a broad phenotypic spectrum.
Although skeletal abnormalities are generally milder in hypochondroplasia than in
achondroplasia, recent advances in prenatal imaging and increasing recognition
of affected neonates have enabled earlier radiographic diagnosis.
Characteristic findings, including iliac hypoplasia and proximal femoral
scooping in neonates, and iliac hypoplasia, short femoral necks, and
metaphyseal flaring in childhood, provide important diagnostic clues. However,
individuals with mild phenotypes may exhibit only subtle skeletal
abnormalities, making it difficult to differentiate them from those with constitutional short
stature. Therefore, when clinical and radiographic findings suggest hypochondroplasia,
confirmation via FGFR3 genetic testing is
recommended. This diagnostic guide summarizes key age-specific radiographic
features and emphasizes an integrated diagnostic approach for the early
recognition and definitive diagnosis of hypochondroplasia.