A 45-year-old male presents with significant bilateral lower limb edema. Physical exam: BP 120/82 mmHg, macroglossia, hemorrhagic oral bullae, slurred speech, marked cardiomegaly, grade III systolic blowing murmur at the apex radiating to the left axilla, liver palpable 2 cm below costal margin with firm consistency, spleen palpable 2 cm below costal margin with hard consistency, ascites sign (+), prominent pitting edema in both lower limbs. Hb 95 g/L, urinary protein (++++), 24-hour urinary protein quantification 4.5 g, disc electrophoresis shows high molecular weight proteinuria, serum albumin 32 g/L, serum creatinine 180 μmol/L, CXR shows generalized cardiomegaly with bilateral pleural effusion. The patient has a history of frequent diarrhea with unremarkable stool studies. The most likely diagnosis is: