What does White guilt feel like, how does it socially manifest itself & is it treatable? White guilt would appear to be a genuine phenomenon which only White people can ever experience - and yet many people deny that it exists, at all, or that it is a form of phoney Liberalism or, worse, "reverse racism".

However, such denials are suggestive of the very thing being denied. White guilt thus appears to feature characteristics of emotional self-indulgence, anger and the desire for forgiveness &amp; personal acceptance.

Is White guilt the same or similar to other forms of guilt, or does it have its own unique characteristics setting it apart from other functions of the human conscience?

White guilt
Given the asker's assertion (in a comment) that


  White guilt results in Black people being killed


here's a repetition of what is usually meant by this term (copied from Wikipedia):


  White guilt is the individual or collective guilt felt by some white people for harm resulting from racist treatment of ethnic minorities by other white people both historically and currently in the United States and to a lesser extent in Canada, South Africa and the United Kingdom.


Like all guilt, White guilt is associated with intentions of making amends toward victims. I think the OP's comment and the question are prompted by a failure to distinguish guilt as a psychological process and guilt as a legal concept.

Psychological guilt only exist if it is interiorized. A psychopath can be judged guilty by a court but feel no (psychological) guilt whatsoever himself. Here's a primer on guilt, in the psychological sense:


  Guilt may be defined as the dysphoric feeling associated with
  the recognition that one has violated a personally relevant
  moral or social standard. [...]
  
  In principle, guilt may be characterized as having both adaptive
  and maladaptive consequences. On the one hand, guilt
  experienced at moderate levels is described as serving a positive
  social function in inhibiting anormative behavior or, in the
  event of transgression, in stimulating impulses to make restitution
  and seek forgiveness (Ausubel, 1955). On the other hand,
  excessive or inappropriate guilt is also assumed to result in
  dysfunctional and disruptive experiences and, in some cases,
  clinical disorders (Lewis, 1971). 


And regarding White guilt, here some of its correlates:


  In two studies, the authors investigated guilt as a response to group-based advantage. Consistent with its conceptualization as a self-focused emotion, White guilt was based in self-focused beliefs in racial inequality. Thus, guilt was associated with belief in White privilege (Study 1) and resulted from seeing European Americans as perpetrators of racial discrimination (Study 2). Just as personal guilt is associated with efforts at restitution, White guilt was predictive of support for affirmative action programs aimed at compensating African Americans. White guilt was not, however, predictive of support for noncompensatory efforts at promoting equality, such as affirmative action programs that increase opportunities (Study 2). In contrast, the other-focused emotion of group-based sympathy was a more general predictor of support for different affirmative action policies. Our findings demonstrate the benefits and limits of group-based guilt as a basis of support for social equality and highlight the value of understanding the specific emotions elicited in intergroup contexts.


So (to state the obvious) white guilt not unique in the sense that it's part of a larger category of "group-based guilt", sometime called "collective guilt". Another example of the latter that has been investigated a fair bit is German collective guilt with respect to the Nazi atrocities (and I'm not talking about guilt in the legal sense here, but the psychological one.) Likewise for colonial injustices. And since in this latter case the perpetrators were usually white, while the victims were not... here's the abstract:


  An investigation of the role of group-based shame and guilt in motivating citizens of ex-colonial countries to support restitution to former colonized groups which were the target of violence and oppression. Study 1 (N = 125) was conducted in Australia during the lead-up to the first official government apology to Aboriginal Australians. Among white Australians, guilt and shame were associated with attitudinal support for intergroup apology and victim compensation. However, only shame was associated with actual political behaviour (signing a petition in support of the apology). Study 2 (N = 181), conducted in Britain, focussed on Britain’s violent mistreatment of the Kenyan population during decolonization. It tested a hypothesis that there are two forms of shame—essence shame and image shame—and demonstrated that image shame was associated with support for apology, whereas essence shame was associated with support for more substantial material and financial compensation.


Since guilt and shame aren't easily delineated, you you'd have dive into the paper for their specific definitions. (The paper is open access, so I'm not going to reproduce all their definitions here.)



Guilt is not considered a mental disorder per se. There are no proposed treatments for guilt by itself, if by "treatment" you mean the usual sense of the word (medical, psychological). Making reparations could be considered a "treatment" for some very loose meaning of the word.

See Bybee and Quiles (1998) for a proposed framework for relating (type of) guilt to mental illness in general. Since this is a book chapter and lacks an authors' summary, here are two (one from the publisher, which is mostly quoting the conclusion section of the chapter, and another form the psycNET; the latter is mostly listing chapter sub-headings)


  Guilt plays a prominent role in cognitive theories of mental illness as well. Guilt has been associated with a number of internalizing disorders, but most frequently with depression. When guilt is chronic, it becomes closely linked with symptoms of mental illness. Perhaps the most important implication of the present work is the importance of alleviating guilt constructively and effectively. Lewis suggests that reaction formation or sublimation might be therapeutic for the individual experiencing chronic guilt. Even if the other person is dead, the guilty individual might provide indirect reparation by giving to charity in memory or honor of the deceased or by providing social or financial support to the deceased person's family. [...] Individuals might be encouraged to seek forgiveness for transgressions they have committed even when these lapses occurred long ago. Indeed, if guilt feelings are still operative years later, this may provide all the more reason for individuals to work to resolve them.
  
  Is guilt related to mental illness? The authors discuss a theoretical perspective intended to address and elucidate relationships between guilt and symptoms of mental illness. The basic principles of the model are: (1) Two fundamentally different forms of guilt exist that show radically different relationships to mental health. (2) Predispositional guilt, no matter how intense, is not maladaptive. (3) Chronic, unalleviated guilt is maladaptive. (4) Predispositional guilt is related to fewer symptoms of externalizing disorders and sociopathy. (5) Predispositional guilt is distinguishable from cognition, knowledge, and moral standards: guilt, not moral standards, is related to prosocial behavior. 
  (6) Chronic, unalleviated guilt is associated with more severe symptoms of externalizing disorders. (7) Chronic guilt is distinguishable from shame: both are maladaptive and show distinct relationships to indices of psychopathology. (8) Characteristics of the individual may determine whether guilt is short-lived or chronic, in turn, affecting mental health. (9) Reactions to the precipitating situations may determine whether guilt becomes chronic (or is absent), in turn, affecting mental health. (10) The nature of the guilt-evoking events may determine whether guilt is short-lived or chronic, in turn, affecting mental health. 


And if you wonder what they mean by those two types:


  The central tenet of the present theory is that two fundamentally different variants
  of guilt exist: predispositional guilt, which is a personality proclivity for experiencing
  guilt in response to specific, circumscribed, eliciting situations, and chronic
  guilt, an ongoing condition of guiltiness, regret, and remorse unattached to an
  immediate precipitating event. We argue that these two forms of guilt display profoundly
  different relationships to mental health.


I've only  skimmed the chapter, but they don't seem to discuss any form of collective guilt. I don't know if there is any research relating some form of collective guilt to (some) mental illness.

Also note that reactive formation is a psychoanalytic theory, so it may not have much empirical basis. Likewise for sublimation.