"Severe transient hypertrophic cardiomyopathy in an extremely preterm infant receiving early low-dose hydrocortisone for bronchopulmonary dysplasia prevention".

We present a case of a 24-week gestation neonate who developed severe, reversible hypertrophic cardiomyopathy (HCM) with mid-cavity obstruction within the first 14 days of life. This occurred while the infant was receiving early low-dose hydrocortisone therapy according to the PREMILOC protocol. The patent ductus arteriosus (PDA) was small and functionally restricted following concurrent medical management with paracetamol at the time of diagnosis of HCM. Genetic, endocrine, and metabolic causes were ruled out, and the infant was not receiving any other pharmacological therapy associated with HCM. Our case highlights the need for clinical awareness of the potential association between HCM and low-dose hydrocortisone. This is a rare occurrence and may represent a multifactorial response involving heightened myocardial stress induced by hydrocortisone and increased left ventricular afterload following PDA restriction. The resulting rise in hemodynamic burden could contribute to cardiac remodeling, highlighting the need for clinical caution, close cardiac monitoring, and further research in this vulnerable population.