Hypertrichosis associated with the use of C-type natriuretic peptide analogue: a case report

Achondroplasia is the most common form of disproportionate skeletal dysplasia. Recently, C-type natriuretic peptide analogue (vosoritide) was approved in numerous countries to increase annual growth velocity in patients with achondroplasia with open plates. This is a case report highlighting an atypical adverse event in a group of patients with achondroplasia using vosoritide for at least 3 months. This adverse event is reported for the first time in the literature. Among all vosoritide clinical trials, hypertrichosis was not described as a side effect.

The study included a total of 18 patients, all of whom were from Brazil. Among these patients, 16 identified as White, specifically Latin Americans of European descent, while the remaining 2 identified as being of African descent. All patients exhibited typical clinical features of achondroplasia, which were confirmed by the presence of the most common pathogenic variant in the FGFR3 gene, c.1138G>A (p.Gly380Arg). Out of 18 patients (11 girls and 7 boys) ranging in age from 2 to 10 years, 11 developed hypertrichosis (8 girls and 3 boys). Out of the 18 patients (61.1%) receiving regular subcutaneous vosoritide, 11 developed hypertrichosis, characterized by pigmented, thin, and short hair on the face, arms, abdomen, back, and legs. Hypertrichosis was clinically diagnosed by experienced pediatric endocrinologists. None of the patients exhibited signs of virilization, advanced bone age, or elevated androgen levels. The hypertrichosis resolved after discontinuation of treatment.

This unexpected pharmacological event, observed in a real-world setting, should be discussed with families prior to initiating treatment. Although hypertrichosis was not previously reported in clinical trials, it was not considered a serious adverse event. Further real-world data are needed to support therapeutic decisions and set appropriate expectations for families, patients, and healthcare providers. Additional evidence is required to better understand the pathophysiology underlying this phenomenon. In some cases, this undesirable adverse effect may influence clinical decision-making regarding treatment.