Costello Syndrome: A Case Report and Literature Review

We present the case of an 8-month-old male infant referred for poor weight gain, with a history of intrauterine growth restriction (birth weight: 2,230 g; height: 45 cm).Physical examination revealed dysmorphic features, including a broad forehead, depressed nasal bridge and low-set ears.Karyotype was 46, XY.Given suspicion of endocrine involvement, a dynamic growth hormone (GH) test with glucagon was performed and showed a peak GH level 3.5 ng/mL, consistent with GH deficiency.Trio whole-exome sequencing identified a heterozygous pathogenic variant in the HRAS gene, confirming the diagnosis of Costello syndrome.This case highlights the importance of considering syndromic etiologies and the RAS/MAPK pathway in infants with failure to thrive, as well as integrating endocrine and genetic evaluations to enable timely diagnosis.