The American Academy of Optometry’s 2017 meeting included a number of classes and workshops dedicated to the diagnosis and management of Demodex. Demodex folliculorum, and its cousin Demodex brevis, are parasitic/commensal face mites found in human hair follicles primarily around the cheeks, nose, eyebrows, eyelashes, and forehead. Demodex overpopulation has been proposed as an instigator of rosacea and blepharitis.
I am confident that you daily encounter patients who have self-diagnosed their ocular condition via an internet search. In fact, an internet “blepharitis” query pulls up information regarding the causes of blepharitis from the respected Mayo Clinic (www.mayoclinic.org/diseases-conditions/blepharitis/basics/causes/con-20024605 ; Demodex are included in the differential diagnosis. It is no surprise, therefore, that patients who carry the diagnosis of blepharitis may question whether the Demodex mite is contributing to their malady.
Possible Impact of Demodex Diagnosis
Formication, a sensation resembling that of insects crawling on or under the skin, is a specific form of the general set of abnormal skin sensations known as paresthesias (prickling, tingling sensation of “pins and needles”) and tactile hallucinations. Formication is a well-documented symptom that has numerous possible causes (Hinkle, 2000). These skin sensations can be a physical or psychological side effect of substance abuse, diabetic neuropathy, diseases of the spinal cord and peripheral nerves, multiple sclerosis, or alcohol withdrawal. It is associated with autoimmune disease, hepatic disease, thyroid disease, lymphoma, arthritis, and stress. A number of prescription and recreational drugs may also cause formication.
Interestingly, a small percentage of menopausal women report itchy skin symptoms or formication. In fact, skin paresthesias are included in the Kupperman/Modified Kupperman Menopausal Index. The Kupperman Index (Kupperman et al, 1953), along with the Menopausal Rating Scale (Hauser et al, 1994), are tools for the assessment of menopausal complaints.
It should be noted that susceptible individuals who fixate on the sensation of formication may develop delusional parasitosis (also known as Ekbom or Morgellons syndrome) (Freudenmann and Lepping, 2009). Classified as a primary psychiatric disorder, affected patients have no primary skin pathology; all skin findings are secondary to skin manipulation by patients, for example, excessive scratching. The prototypical patient is an older woman.
Patients who have this disorder may be fully functional, but have a false belief that they, and perhaps their home environment, are infested with parasites despite repeated reassurances from physicians, pest control experts, and other professionals that they are not.
Often, patients who have delusional parasitosis will report to have the offending parasites in a collection of material (typically pieces of skin, scabs, hair, lint, dried blood, living organisms such as flies or ants, and other debris) and request to have it studied for identification. This clinical presentation is called the “specimen sign” (Mehmood and Khasawneh, 2014) or the “matchbox sign,” as patients have often used a matchbox to collect the material (Freudenmann and Lepping, 2009).
Be on the Lookout
Recent clinical experience from practices across the country (personal communications) has raised my awareness of delusional parasitosis. I urge practitioners to thoroughly process a patient’s complaints and medical history before assigning disease culpability to the ubiquitous mite. To wit, careful monitoring of a patient’s emotional demeanor is paramount when managing diagnosed Demodex overpopulation. CLS
For references, please visit www.clspectrum.com/references and click on document #265.