A 35-year-old male was admitted for evaluation after routine urinalysis revealed proteinuria (++), 0-5 RBCs/HP, and 0-1 granular casts/HP. Further tests showed lipiduria and 24-hour urinary protein quantification of 0.98g. Physical examination revealed clustered dark-red telangiectasias on the lower abdomen, conjunctival and fundus vascular dilatation, moderately elevated BP, and leftward cardiac enlargement. Blood tests showed normal renal function but markedly reduced α-galactosidase A activity. Renal biopsy demonstrated foamy enlarged parietal epithelial cells in Bowman's capsule. The most likely diagnosis is: