Classification & external resources
Hypochondroplasia is a developmental disorder caused by an autosomal dominant genetic defect in the fibroblast growth factor receptor 3 gene (FGFR3) that results in a disproportionately short stature, micromelia, and a head that appears large when compared with the underdeveloped portions of the body. It is also known as "achondroplasia tarda" and "atypical achondroplasia."
People affected by this disorder appear normal at birth. As the infant grows, however, their arms and legs do not develop properly and their body becomes thicker and shorter than normal. The head is normal but appears large due to the underdevelopment of other parts of the body, a symptom called "relative macrocephaly".
The clinical and radiographic features of this disorder are milder than those seen in achondroplasia.
Intelligence is usually normal.
This disorder results from mutations in the proximal tyrosine kinase domain of the FGFR3 gene. This gene plays an important role in embryonic development, playing a part in regulating activities such as cell division, migration, and differentiation.
Standard treatment of hypochondroplasia usually takes the form of orthopedic surgery and physical therapy. Genetic counseling is advised for patients and their families.
This disorder is transmitted as an autosomal dominant trait affecting the FGFR3 gene on chromosome 4p16.3.
Females tend to be affected more often than males.
- ^ Santos HG, Almeida M, Fernandes H, Wilkie A (2007). "Clinical hypochondroplasia in a family caused by a heterozygous double mutation in FGFR3 encoding GLY380LYS". Am. J. Med. Genet. A 143 (4): 355–9. doi:10.1002/ajmg.a.31556. PMID 17256796.
- ^ Rousseau F, Bonaventure J, Legeai-Mallet L, et al (1996). "Clinical and genetic heterogeneity of hypochondroplasia". J. Med. Genet. 33 (9): 749–52. PMID 8880574.
- ^ Heuertz S, Le Merrer M, Zabel B, et al (2006). "Novel FGFR3 mutations creating cysteine residues in the extracellular domain of the receptor cause achondroplasia or severe forms of hypochondroplasia". Eur. J. Hum. Genet. 14 (12): 1240–7. doi:10.1038/sj.ejhg.5201700. PMID 16912704.
|Congenital malformations and deformations of musculoskeletal system (Q65-Q79, 754-756)|
|Limbs||hip: Dislocation of hip/Hip dysplasia
feet (Club foot, Flat feet, Pes cavus)
head, face, spine and chest: skull, face and jaw (Dolichocephaly, Plagiocephaly) - Scoliosis - chest (Pectus excavatum, Pectus carinatum)
Polydactyly/Syndactyly (Webbed toes)
reduction deficits (Ectrodactyly, Amelia, Phocomelia)
upper limb (Cleidocranial dysostosis, Madelung's deformity, Sprengel's deformity)
knee (Genu valgum, Genu varum)
|Skull and face bones||Craniosynostosis (Scaphocephaly) - Trigonocephaly - Oxycephaly - Crouzon syndrome - Hypertelorism - Macrocephaly - Treacher Collins syndrome - Platybasia|
|Spine and bony thorax||Klippel-Feil syndrome - Spondylolisthesis - Cervical rib - Bifid rib|
|Osteochondrodysplasia||growth of tubular bones and spine: Achondrogenesis - Thanatophoric dysplasia - Short rib-polydactyly syndrome - Chondrodysplasia punctata (Rhizomelic chondrodysplasia punctata, Conradi-Hünermann syndrome), Achondroplasia (Hypochondroplasia, Osteosclerosis congenita) - Ellis-van Creveld syndrome - Spondyloepiphyseal dysplasia congenita|
Osteogenesis imperfecta - McCune-Albright syndrome - Osteopetrosis - Metaphyseal dysplasia - Hereditary multiple exostoses - Osteopoikilosis - Chondrodystrophy - Osteodystrophy
|Other||abdominal wall (Congenital diaphragmatic hernia, Omphalocele, Gastroschisis, Prune belly syndrome) - Ehlers-Danlos syndrome|
|See also non-congenital conditions (M, 710-739)|