Case Report: Possible improvement of near-adult height with PEG-rhGH and letrozole in a late-puberty boy with atypical Noonan syndrome and bone age/height age discrepancy: a novel therapy

Background: Noonan syndrome (NS) is a rare congenital disorder predominantly characterized by short stature, with recombinant human growth hormone (rhGH) as the primary treatment. This study aimed to investigate the effects of a novel therapy involving pegylated (PEG)-rhGH and letrozole on near-adult height (NAH) improvement in a boy with NS who was undergoing late-puberty and presented with higher bone age (BA) than height age (HA). Case presentation: ) improved by 1.62. Additionally, there were no significant changes in thyroid function, blood glucose, uric acid, and IGF-1 levels during the treatment period, which fluctuated within the normal range. The patient had a transient slight elevation in testosterone, but normalized spontaneously, and the patient reported no discomfort. Besides, he experienced mild facial acne, but resolved without additional intervention after letrozole discontinuation. No other obvious adverse reactions were observed. Conclusion: The novel therapy of PEG-rhGH and letrozole demonstrated promising potential in improving NAH, while adhering to safety profiles. This case represented the first attempt to use this dual therapy for NAH enhancement in an adolescent boy with NS and a higher BA than HA.