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Growth Hormone Treatment in Patients with Hypochondroplasia

plasia with developmental delay and acanthosis nigricans, achondroplasia, and HCH [4] . The most commonly found genotype for patients meeting clinical and radiographic criteria for HCH is the N540K mutation in the FGFR3 gene on chromosome 4p16.3. Adult heights for patients with the clinical diagnosis of HCH have been reported to vary widely: from 145 to 165 cm in males and from 133 to 151 cm in females [5] . The broad spectrum of adult height lost may be attributable to varying degrees of penetrance even among children with the same FGFR3 genotype [6, 7] . Reports of the benefits of recombinant human growth hormone (hGH) treatment in children with skeletal dysplasias are mixed. In children with achondroplasia, there may be transient improvement in height velocity without improvement in adult height. Thus, the use of hGH to treat achondroplasia is not routinely recommended [4] . For children with HCH, there are no reports of placebocontrolled trials that have evaluated the use of hGH treatment to adult height. Previous reports of patients with HCH suggested an improvement in height velocity when treated with hGH, particularly at the time of the pubertal growth spurt [5, 8] . A report of 6 children with the N540K mutation of the FGFR3 gene treated with growth hormone also showed improvement in height velocity and trunk/leg disproportion; however, the study lacked control patients for comparison and the patients were not followed up to adult heights [9] . In children evaluated for short stature or growth failure, subtle skeletal dysplasias may be difficult to identify, particularly before puberty when skeletal disproportions are less obvious. Children with mild forms of skeletal dysplasias, including hypochondroplasia (HCH), may be mislabeled as having ‘growth failure of unknown etiology’, otherwise known as ‘idiopathic short stature’ [1] . Patients with HCH have also been labeled as ‘small for gestational age’ or having ‘familial short stature’ [2] . Stimulation testing has occasionally been performed in patients with HCH and some have been diagnosed with growth hormone deficiency that was not reproduced on subsequent testing [3] . Correctly identifying children with skeletal dysplasias is important to establish appropriate treatment regimens as well as manage expectations for short-term growth and adult height. The diagnosis of HCH can be established by clinical, radiographic, and genetic testing. Clinically, children with HCH may have short stature, an increased upper-to-lower segment ratio, short arm spans, and macrocephaly. Radiographic abnormalities include decreased interpedicular distances between lumbar vertebrae L1 and L5 and short lumbar pedicles in the absence of other gross radiographic abnormalities. FGFR3 mutations have been reported in subjects with skeletal dysplasias. The phenotype of affected individuals varies according to the FGFR3 mutation and ranges from thanatophoric dysplasia to severe achondroPublished online: December 16, 2014 HORMONE RESEARCH IN PÆDIATRICS