My 18 Year Old Nephew Has Lost Weight Extremely Fast,

My 18 year old nephew has lost weight extremely fast, he went from 333 to 172 in less than a years time, his heart rate last checked was 130 plus, he has two knots on the back side of his neck, he is yellowish colored skin, and his lips are pale in color almost white. He can hardly eat. He has no energy. His finger nails are receded and brittle. I am extremely concerned.