False-negative 99mTc-PYP bone scintigraphy in early cardiac amyloidosis: a rapidly progressive case in a young woman.

Cardiac amyloidosis is one of the aetiologies of treatable heart failure. Cardiac amyloidosis is rare in young patients, but it can present atypically, leading to diagnostic delays. In this case, a 33-year-old female patient presenting with dyspnoea underwent echocardiography and cardiac magnetic resonance imaging, which showed left ventricular hypertrophy and raised suspicion for amyloidosis; however, no uptake was observed on technetium-99m pyrophosphate (99mTc-PYP) bone scintigraphy. Fourteen months later, the patient presented with decompensated heart failure and was diagnosed with cardiac amyloidosis based on Grade 2 uptake on repeat 99mTc-PYP bone scintigraphy, with an ejection fraction of 25%. As illustrated in this case, negative imaging findings in the early stages do not rule out a diagnosis of cardiac amyloidosis.