Word for the opposite of “hypochondriasis” This question was posted in English.stackexchange.
    


  Is there a word for the opposite condition of hypochondriasis? For
  example, someone who denies being sick when they clearly are? I would
  just say that they are "in denial". Is there any other adequate
  word?


Some answered egosyntonic. Is it correct?

P.S. Credits to Renan
It seems to depend on the reason for denying their illness...

Egosyntonic:


  ... a term referring to behaviors, values, feelings that are in
  harmony with or acceptable to the needs and goals of the ego, or
  consistent with one's ideal self-image. ... Many personality disorders
  are considered to be egosyntonic ... Anorexia ... is also considered
  egosyntonic because many of its sufferers deny that they have a
  problem.


People with personality disorders for example, may be fully aware and accepting of their behaviour, they simply don't see it as a problem.

Denial / abnegation:


  ... is used for a psychological defense mechanism ..., in which a
  person is faced with a fact that is too uncomfortable to accept and
  rejects it instead, insisting that it is not true despite what may be
  overwhelming evidence. ... In denial, an individual does not see or is
  mostly unconscious of existence of the truth or fact. The choice to
  refuse reality, then, is unconscious as well.


Someone may deny their illness because it makes them uncomfortable in some way - eg, they are embarrassed about it or concerned about negative perceptions by others.

Anosognosia:


  ... a deficit of self-awareness, a condition in which a person who
  suffers a certain disability seems unaware of the existence of his or
  her disability. ... Anosognosia is relatively common following
  different etiologies of brain injury ..., but can appear to occur in
  conjunction with virtually any neurological impairment.


In Anton–Babinski syndrome (visual anosognosia) for example, a person is blind, but nonetheless claims to be able see, and this is due to brain damage in the visual cortex.

Hypochondria is undue alarm about any physical or psychological symptoms, no matter how minor they may be.  So I would argue that the best counterpart is minimisation - a cognitive distortion:


  ... is the opposite of exaggeration. ... downplaying the significance
  of an event or emotion ...


A medical condition that fits this description is anosodiaphoria:


  ... a condition in which a person who suffers disability due to brain
  injury seems indifferent to the existence of their handicap. ... a
  disorder of the body schema in which patients verbally acknowledge a
  clinical problem ... but fail to be concerned about it.


So while a hypochondriac makes a big deal out of a small problem, anosodiaphoria is making a small deal out of a big problem.

Also see hyperchondria.