Growth Hormone Treatment in an Adolescent with Pycnodysostosis

Introduction: Pycnodysostosis is a rare skeletal dysplasia caused by autosomal recessive mutations in the cathepsin K (CTSK) gene and is characterized by short stature, osteosclerosis, and large fontanels. Adult height varies between 130 and 150 cm. Here, we report the short-term effect of growth hormone (GH) treatment in an adolescent with pycnodysostosis.
Case: A 7-year-old boy presented with a compliant of short stature. He was born at 37th gestational week, weighing 2400 g. His parents denied consanguinity, but they were from the same village. His height was 106.3 cm (SD score -2.85). He had typical clinical (open anterior fontanel, frontal bossing, prominent nose, brachydactyly, and teeth abnormalities) and radiological features (widened lambdoid sutures and anterior fontanel, hypoplasia of the mandible, diffuse osteosclerosis and acroosteolysis in the distal phalanges). Genetic analysis showed homozygous M1I (ATG>ATA) mutation in the CTSK gene, confirming a diagnosis of pcynodysostosis. During a 7-year follow-up without treatment, the patient’s height reached to 133.8 cm (SD score -4.35) with an average annual growth rate of 3.9 cm. Despite the onset of puberty, growth rate was 2 cm/year over the last 6 months. Target height and predicted adult height were calculated as 168.7 cm and 142 cm, respectively. Peak GH responses in two clonidine tests were 3.9 and 9.3 ng/mL, and GH treatment was started at a dose of 2 mg/day (42 µg/kg/day). In the first six months of treatment, growth rate was determined as 9.4 cm/year, which is more than twofold increase.
Conclusion: Few publications demonstrate that GH therapy in patients with pycnodysostosis increases growth rate and provides near-normal adult height in long-term use. Short-term outcome of GH therapy in our case is consistent with the data of previous publications and suggests that early initiation of therapy would be more useful for the patients with pycnodysostosis.