Q. Cat is 15+ yrs old, weight loss from 6.5 lb. To 4 lb, gaunt & bony. Coat looks almost greasy & rumpled. She looks better after egg yolk in morning.
DR. MASSIMO ORIOLES, DVM, MRCVS
A. Severe weight loss is a common sign in old cats and several diseases can cause that (hyperthyroidism, renal failure, gastrointestinal diseases, tumors and many others).
I would definitively recommend to take her to your veterinarian and have her checked. Blood test and urine analysis may be helpful to detect the underlying cause.