Is there a disorder that people have when they lie or fake illness?

Answer 1

Yes, it can be a sign of a mental disorder.

Depending on the intent of constant lying about being sick in any way, whether it be mentally, physically, or both the causes are usually due to a factitious disorder or a malingering disorder, and both disorders are characterized by pretending to be sick when the person is well aware that they are in fact not.

With a malingering disorder one pretends to be mentally ill to escape responsibility or to gain a financial reward, and this is evident in many plea bargains where a defendant of a heinous crime tries to get off by feigning a mental illness. (source:minddisorders.com)

On the other hand, there is the factitious disorders, where pretending to be sick both mentally or physically, or both is simply used for attention, sympathy or to satisfy that person's need to be seen as weak or sick by others.

One factitious disorder to note in particular is Maunchism, and is the worst case of a factitious disorder, where the act of being sick is even more excessive and many times self-induced. (source: myclevelandclinic.org)

Both are not to be confused with hypochondria or other somatoform disorders. (source: familydoctor.org)

Answer 2

i think its called being a hypochondriac, but i might be wrong. not sure if that's the right spelling either...