Subtle echocardiogram findings requiring further investigation: restrictive cardiomyopathy in a rare genetic condition.

Mulibrey nanism (MN) is a extremely rare genetic condition first described in 1973, with around 150 cases reported worldwide. MN is characterised by growth delay and multiorgan manifestations, the most fatal being a combination restrictive-constrictive, perimyocardial heart disease that results in diastolic heart failure. We present a male toddler with MN who presented with recurrent episodes of hypoxia, feeding intolerance, and generalised swelling (anasarca) in the setting of subtle echocardiographic findings. A multidisciplinary and systematic diagnostic approach was used to determine the underlying aetiology. Invasive cardiac testing via right heart catheterisation revealed the final diagnosis of restrictive cardiomyopathy. Transplant decision-making was limited due to hepatic involvement. This case highlights the limitations of echocardiography in diagnosing restrictive cardiomyopathy, which has a preserved ejection fraction, as well the need for multidisciplinary involvement and a family-centred approach in treating patients with this rare condition.