Delusional Parasitosis

A new study looks into the disorder known as delusional parasitosis, which many dermatologists believe is the true diagnosis behind the controversial disorder called Morgellon’s disease. Morgellons is a controversial disorder because many patients with symptoms believe they are being infected by an unusual organism, causing excessive itching, but no offending organism has been found. Some patients claim they have strange fibers exuding from the sores in their skin.

The term “Morgellons” was coined in 2002 by Mary Leitao, who was trying to find a diagnosis for her son who was suffering from skin lesions. Since then it has become a grassroots diagnosis – used by some patients to describe themselves but not accepted by the medical community.

Most dermatologists, rather, feel that the disorder is actually a manifestation of delusional parasitosis – a mental disorder. This has set up an unnecessarily confrontational situation. And of course, some charlatans are exploiting the situation by taking the side of the patients and offering them their nostrums as a cure.

These situations are always helped, but rarely resolved, by better information. It is in this context that Hylwa et al performed a retrospective analysis of patients diagnosed with delusional parasitosis at the Mayo dermatology clinic. They analyzed records from 108 patients who had either a skin biopsy (80 patients) or presented their own sample (a patient-provided specimen – also 80 patient), or both (52 patients).

They found that in all 108 cases no evidence of infection or infestation was found.

They did find, however, that 48% of biopsies showed dermatitis – inflammation of the skin. This finding has two plausible interpretations. The first is that in some patients with delusional parasitosis, they may have an underlying skin condition that causes non-specific dermatitis (an allergy, for example) and the symptoms of this dermatitis triggers the psychological reaction that results in the belief that they are infested with something foreign. In this case they could be simply misinterpreted their skin sensations. Further the chronic symptoms can cause stress and lack of sleep and result in the anxiety and depression that often accompanies this disorder.

The other plausible interpretation is that the dermatitis is secondary to scratching and perhaps treating the skin with irritating substances intended to treat the problem. The current study is not capable of distinguishing between these two possibilities.

The authors acknowledge the limitations of this study – mainly that it was retrospective. It also needs to be considered that their search criteria was for patients diagnosed with delusional parasitosis – not all patients with unknown or mysterious skin lesions. In that respect the results are not surprising – the diagnosis may result from a negative biopsy or sample analysis, and so of course patients with that diagnosis will have had a negative biopsy.

The authors do not even address the controversy surrounding Morgellons. Rather they are asking if skin biopsy is useful in patients presenting clinically with delusional parasitosis. Again – given the retrospective nature of this study I don’t think it answers that question.

This study does, however, review a large series of cases demonstrating a lack of biopsy or sample analysis findings in patients who fit within the clinical syndrome that is labeled as either Morgellons or delusional parasitosis. It should further be noted that those who claim that Morgellons is a distinct disease caused by a skin infestation cannot point to any objective evidence of an actual infestation to support that claim.

What proponents do have are mysterious fibers sometimes found in the skin lesions of people with this syndrome. The fibers often cannot be specifically identified, or they are identified as foreign fibers consistent with clothing. They usually do not appear to be of organic origin. At best the fibers represent an anomaly, and are not specific evidence of any underlying cause.

What is especially disturbing about the Morgellons phenomenon is the tone of the discussion, the extent to which the controversy has been politicized. Often irrelevant issues are brought to the forefront, such as patient empowerment or medical authority. Not that these issues are not important – they are just not relevant to the real question of what, exactly, is the underlying cause of what is referred to as Morgellons.

Patients who suffer from this syndrome are best served by bringing objective scientific evidence to bear to discover exactly what the cause(s) and best treatments for their symptoms are. But this issue is often derailed by accusations that the medical community is dismissing them and their claims. By grabbing the reigns of diagnosis and treatment such patients are given a false sense of empowerment, but are likely just cutting short earnest attempts to understand and treat their condition.

And of course, good science has to follow the evidence wherever it leads, even if the answer is not what is hoped. The truth does not care what people need or want – it is what it is.


This latest study will likely not change the debate about Morgellons vs delusional parasitosis. Although it should be kept in mind that delusional parasitosis (DP) is a disorder in its own right, and pre-existed any notion of Morgellons. Morgellons is likely just a recent manifestation of DP – a cultural entity spreading mainly on the internet. It should also be noted that DP likely contains two or more subgroups that have distinct causes – such as the two causes of dermatitis I discussed above.

At present there is no compelling evidence that Morgellons exists as a discrete entity separate from DP. The CDC is currently studying the condition (which they are calling unexplained dermopathy) but has not yet made any report of their findings.

My review of the evidence is that it best supports the conclusion that Morgellons is a mostly a psychocultural condition (it may be triggered in cases by an underlying skin condition). It is a combination of a cultural phenomenon spreading mostly online, giving specific manifestation to an underlying psychological condition. I am willing to be convinced that there is a biological process going on, but so far no compelling evidence to support this hypothesis has been put forward.

I also think that specific harm can be done to individuals with this syndrome by the spread of false information. Sufferers can easily be made to settle prematurely on a false conclusion, and in fact can reinforce their delusions if that is ultimate cause of their symptoms. They can be lured away from practical interventions and the medical community to dubious treatments that are, if nothing else, a waste of their resources.

The situation represents a challenge to the medical community. Perhaps the only solution is to explain and promote the scientific approach to diagnosis and treatment.

Posted in: Neuroscience/Mental Health

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