Hello Doc My Dogs A 12 Year Old Shizuoka. Normally

Hello Doc my dogs a 12 year old Shizuoka. Normally in good health but he has suddenly lost a great deal of his body fat very shockingly bony. He has very large swollen lymphnoids and urinates more frequently his appetite still seems normal though. He has very different sounding breathing belaboured pretty sluggish. Have you any ideas