Diagnostic ConsiderationsMedical diagnoses to be consideredPsychiatric diagnoses to be considered
Factitious disorder appears in the differential diagnosis for many illnesses. Accordingly, it must be distinguished from a true or real general medical condition or mental disorder, including those that are (1) due to accident or chance, (2) due to noncompliance with treatment, (3) iatrogenic, or (4) the result of attempted suicide, homicide, or self-mutilation.
The initial presentation of patients with factitious disorder always suggests a medical or psychiatric problem, exhibiting features compatible with the ailment being feigned or produced. The ruses patients may employ are limited only by their creativity, knowledge, and motivation and may include esoteric diagnoses of which most doctors would be largely unaware.
When routine examination and testing fail to confirm any of the most obvious diagnostic possibilities, factitious disorder should be excluded. At this juncture, clinicians should consider various idiopathic medical illnesses that have a fluctuating course or that manifest across several different organ systems, though these can be enacted as well (eg, multiple sclerosis and systemic lupus erythematosus). The case literature suggests that the most frequent medical diagnoses among patients who are falsely believed to have factitious disorder or conversion disorder are as follows:
Central nervous system (CNS) diseases (eg, encephalopathy)
Structural diseases of the muscles and connective tissue
In creating a working list of hypotheses for the diagnosis of a puzzling medical case, it is important to follow base-rate information about the frequency of each diagnostic possibility. If this procedure were followed, factitious disorder would probably emerge as the third to fifth most likely diagnosis in such cases.
Even if factitious disorder occurred only once per 10,000 patients (a frequency that is probably an underestimate), it would still be more prevalent than some of the exceptionally rare disorders that a physician might consider before entertaining the possibility that the patient is feigning illness. Cases abound in which doctors have bypassed consideration of factitious disorder as they repeatedly performed more tests, further medication trials, and additional surgeries or applied literally novel diagnoses.
Factitious disorder and Munchausen syndrome must be distinguished from certain related types of clinical psychiatric problems.
The first of these related conditions is simple malingering. Though not an official mental disorder, it can sometimes be a focus of clinical attention. In malingering, symptom production is both intentional and conscious, aimed at achieving an external incentive beyond the sick role itself (though it is sometimes hard to identify this incentive with certainty). Examples of external goals are acquiring narcotics, evading criminal prosecution, gaining disability payments, and avoiding military service.
In practice, diagnosis almost always requires a weighing of internal and external incentives, because the sick role itself almost always includes rewards and dispensations of various kinds (eg, financial assistance that a church insists the patient accept). The external goal in malingering is usually obtained by first securing a physician’s official confirmation of an authentic illness or injury.
Typically, a malingering patient will abide only as much testing and treatment as is necessary to achieve his or her aims. In contrast, a person with factitious disorder imposed on self will actively attempt to maintain the sick role and will willingly undergo as much testing and treatment as possible.
Other related conditions from which factitious disorder must be distinguished are somatic symptom and related disorders, particularly illness anxiety disorder. In these disorders, the symptoms of illness are not produced intentionally, and the motivation for illness is unconscious, whereas in factitious disorder, symptoms are produced intentionally but for reasons that may be unconscious.
In illness anxiety disorder, the patient presents with anxiety, and either no physical signs are present and objective test findings are within normal limits or a medically insignificant sign is noted (eg, discoloration of the skin). The patient may insist, with true conviction, that he or she is gravely ill and may demand various tests. When the results of the tests are negative, the patient is typically relieved, at least for a short time.
In its typical form, this presentation is not easily confused with factitious disorder; however, in rare instances, the patient is so strongly convinced of being gravely ill that he or she resorts to simulation or self-injury as a means of soliciting further diagnostic testing. The differential diagnosis may thus depend on subtle signs such as the presence or absence of relief when the patient is informed of negative test results and the patient’s willingness to permit caregivers to communicate with each other and with family members.
Factitious disorder must also be distinguished from somatic symptom disorder and conversion disorder. In general, the distinction is made on the basis of the belief that patients with the latter disorders do not intentionally exaggerate or feign illness. In practice, however, it may be impossible to distinguish between somatic symptom disorder and factitious disorder in patients who do not carry out physical simulations or self-injury that might provide concrete evidence of intentional deception.
Patients with other psychiatric diagnoses can also present with somatic preoccupation that is not supported by findings from physical examination, laboratory testing, or imaging. Patients who have major depression with psychotic features and delusional disorder (somatic type) can present with somatic delusions. Associated features of these conditions should facilitate the differential diagnosis.
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