Case Report: A missed diagnosis of cardiac amyloidosis using echocardiography due to immunoglobulin light chain amyloidosis with normal wall thickness in the early stage.

BACKGROUND

Cardiac amyloidosis (CA) is a challenging diagnosis, particularly when the classic signs, such as increased wall thickness in a non-dilated left ventricle (LV), are absent. This makes the diagnosis more difficult in patients with normal LV wall thickness. We present a case of CA without increased wall thickness and without the characteristic granular sparkling echotexture in a non-dilated LV.

CASE SUMMARY: A 50-year-old female patient presented with worsening breathlessness on exertion, paroxysmal nocturnal dyspnea, oliguria, and lower-extremity edema. Electrocardiography showed low voltage in the limb leads and a pseudoinfarction pattern in the anterior leads. The echocardiographic evaluation revealed a non-dilated LV with normal wall thickness, no granular sparkling echotexture of the myocardium, a mildly dilated left atrium, restrictive filling (grade 3 diastolic dysfunction), and pericardial effusion. A follow-up quantitative echocardiographic study 2 weeks later showed a slight increase in LV wall thickness (still within the normal range), decreased global longitudinal strain, and a relative "apical sparing" pattern of longitudinal strain in the apex of the LV. After 1 month, LV wall thickness increased beyond the normal range, and the granular sparkling echotexture became evident. Cardiac amyloidosis was subsequently confirmed by delayed gadolinium enhancement on cardiac magnetic resonance imaging, abnormal serum-free light chain levels, positive serum immunofixation, and an extracardiac biopsy positive for amyloid.

DISCUSSION: Patients presenting with normal wall thickness in a non-dilated LV might only be in an early stage of CA. Thus, the diagnosis can be easily overlooked. For smaller individuals, relative wall thickness (RWT) may be a more sensitive indicator for further investigation. In patients presenting with increased RWT, restrictive filling, and pericardial effusion in the absence of other plausible causes, CA should be considered, even in the absence of the classic echocardiographic signs of amyloid deposition. Furthermore, two-dimensional speckle-tracking echocardiography can enhance clinical suspicion of CA and should be recommended as part of the diagnostic workup.