A 40-year-old man presented to a local clinic complaining of dyspnoea, progressive anaemia, and decreased appetite. N-terminal pro-brain natriuretic peptide (NT-proBNP) was markedly elevated to 12 994 pg/mL, and he was admitted to our hospital. At the first visit, his blood pressure was 84/46 mmHg and pulse rate was 65 b.p.m. with a regular rhythm. Precordial examination revealed a third heart sound. Chest examination revealed bilateral diminished air entry over both lung bases. He displayed oedema of the lower extremities. A blood test indicated markedly elevated levels of BNP (1490 pg/mL). Complete blood count showed anaemia with haemoglobin of 10.9 g/dL. Electrocardiography displayed a low-amplitude R-wave on the limb leads and a QS pattern on leads V1–V3 (). Transthoracic echocardiography revealed moderately increased left ventricular (LV) wall thickness (septal wall, 14 mm; posterior wall, 14 mm) with a small pericardial effusion (). Thickening of the right ventricular (RV) wall was also shown. Left ventricular systolic function was preserved, with an ejection fraction (EF) of 63%, as measured by the modified Simpson method. Longitudinal myocardial systolic strain based on two-dimensional speckle-tracking echocardiography showed far more significant LV dysfunction. Global longitudinal strain was markedly reduced to −6.2%, and bull’s eye mapping revealed the characteristic apical sparing pattern (). The regional values of the RV free wall longitudinal strain (RV free wall LS) were reduced to −7.0% (). Left atrial (LA) strain was also reduced to −14%. The mitral inflow profile showed a restricted pattern such that the patient's peak early filling (E) and late diastolic filling (A) velocity ratio was 3.2. Furthermore, the septal and lateral tissue Doppler e‘ values were low, with an E/e’ ratio >15. Pulmonary artery systolic pressure could not be estimated due to absence of tricuspid regurgitation. Inferior vena cava (IVC) was dilated and showed decreased respiratory variability. These findings led us to strongly suspect CA with heart failure. Cardiac magnetic resonance imaging (MRI) showed diffuse subendocardial mild enhancement of the biventricular myocardium. Subsequently, the patient was diagnosed with primary systemic AL amyloidosis by cardiac muscle, duodenum, and bone marrow biopsy (, ). Although BD treatment (bortezomib + dexamethasone) and medical treatment were started, the patient’s condition gradually worsened. Then, high-dose chemotherapy (melphalan, 140 mg/m2) with auto-PBSCT was started. The clinical course of auto-PBSCT is shown in. Brain natriuretic peptide levels declined to the 200 s pg/mL at 6 months after auto-PBSCT and continued to decrease. Left ventricular diastolic function measurements corresponded to progressive improvement in the BNP level. Doppler demonstrated a relaxation abnormality pattern with an E/A <0.8, and an IVC diameter <15 mm at 6 months after auto-PBSCT. These improvements were accompanied by an improvement in biventricular LS. While GLS showed a slight change at 6 months after auto-PBSCT was started, it significantly improved thereafter. Twenty-two months after auto-PBSCT, GLS improved to a value of −16.2%, and bull’s-eye mapping showed a more normal pattern. Right ventricular free wall LS and LA strain were also improved to −17% and −27%, respectively. Left ventricular EF did not change significantly from pretreatment levels. The anatomic changes in ventricular wall thickness occurred at a slower rate than the changes in GLS. Left ventricular wall thickness improved to 10 mm at 22 months after auto-PBSCT (,, Videos S1 and S2). Interestingly, the subendocardial enhancement disappeared on cardiac MRI after auto-PBSCT. Currently, the patient has had no relapse over 60 months ().