PhotoDx

Do I Have Bug Bites?

Robert Norman, DO; Cory Porteus OMSIII

Volume 21 - Number 9 - September 2013

A 73-year-old woman presented to the office with the chief concern of persistent bug bites and edema that had recently worsened. The lesions covered both arms, from the wrist to mid-humerus, and on both legs, from the toes to just below the knee. Upon physical examination, her upper and lower extremities, particularly her ankles, appeared erythematous, swollen, and scaly with multiple vesicles filled with a clear fluid, and areas denuded of overlying skin. The skin appeared thick and leathery. She described the itching as constant and distracting, and she frequently scratched the lesions to the point of causing bleeding. The edema was nonpitting, and appeared to have been caused by repetitive itching rather than an accumulation of fluid.

The patient was insistent upon parasites as the cause of her discomfort. She claimed that her house was infested with minuscule mites, which were constantly biting her and leaving itchy welts that were unrelieved by any therapy. Despite removing all the furniture and carpet in her house and several visits from an exterminator, she claimed the mites persisted. Her husband, who accompanied her on this visit, confirmed her story and brought a sample of the mites to corroborate her story.

She claimed to have had this mite infestation and the resulting lesions for 6 years. She said the lesions initially appeared on her ankles bilaterally, which she noticed shortly after undergoing a quadruple coronary artery bypass graft surgery, and then spread to all four extremities over time. To treat her lesions, previous physicians had prescribed antihistamines, corticosteroids, and various antibiotics, none of which changed her symptoms. The patient’s medical history included stage 3 chronic kidney disease. She reported fatigue and fluid retention, but no other symptoms. At times during the visit, the patient expressed frustration to the point of tears for being unable to relieve her symptoms. A biopsy was performed on one of the lesions.

Based on the photograph and the case description, what is your diagnosis?

  1. Neurodermatitis
  2. Allergic contact dermatitis
  3. Scabies
  4. Flea bites
  5. Lichen planus

 

Click next page for the answer and discussion>>

Diagnosis: Neurodermatitis (A)

Discussion

We arrived at a diagnosis of neurodermatitis due to the biopsy findings, the absence of any demonstrable ectoparasitic activity, and the presence of multiple excoriations. We also highly suspected she had delusions of parasitosis based on her medical history; clinical picture, including the presence of stage 3 chronic kidney disease; and absence of any mites, including in the sample the husband had brought. Chronic kidney disease is associated with mild to moderate edema and cognitive impairment, including delusions and hallucinations caused by multiple electrolyte disturbances, anemia, and uremia.1,2

The term neurodermatitis encompasses several dermatological conditions sharing an underlying psychological basis. The disorder can result in delusions of parasitosis, lichen simplex chronicus, neurotic excoriations, or prurigo nodularis.3 The disorder commonly results from a cycle of idiopathic itch followed by scratching to relieve, which then worsens the itch. This cycle results in a thickening of the skin, often turning it darker and leathery.4 The cause of the initial itch is unknown, and often the scratch becomes a reflex rendering the initial itch inconsequential.4 Various causes of the initial itch have been proposed, including irritation from fabric or insect bites, psoriasis, and atopic dermatitis.5 Neurodermatitis has been noted in populations of cognitively impaired children with repetitive motion disorders and in elderly individuals with depression or obsessive compulsive disorder.6 Another hypothesis claims it can be triggered by depression, anxiety, or other psychological disorders.6 One of the more common manifestations of the disorder is the belief that insects are causing the itching and lesions, and some patients may claim to feel the bugs crawling on them.

Neurodermatitis generally affects the elderly and tends to affect more women than men.4 The lesions appear as hyperpigmented, thickened skin.5 There are often lesions in various states, from newly appearing erythematous macules to scars from past lesions. They often exhibit a linear pattern, reflecting the involvement of scratching in the pathogenesis of this disorder.3 The extremities are most often involved, and lesions may appear bilaterally. Rarely, the genital regions may be involved.

Histological Findings
A biopsy tends to show several nonspecific findings, including hyperkeratosis due to chronic scratching, thickened epidermis with irregularly elongated rete ridges, and vertically oriented fibrosis and collagen in the papillary dermis.7

Approaches to Treatment
Treatment for neurodermatitis is multifocal. The main goal of therapy is reducing scratching from any cause. Treatment usually involves a protracted course combining cognitive therapy and anti-itch medications. Initial treatment should include topical and systemic glucocorticoids.7 Glucocorticoids can reduce itchiness and redness of affected areas.7 Additionally, treatment may be aimed at decreasing depression or any psychological ailments, if present. Counseling has been successful in encouraging cessation of scratching.5  

Ruling Out the Other Diagnoses

What follows is a brief review of the other possible diagnoses, which were ruled out for our case patient.

Allergic Contact Dermatitis
Allergic contact dermatitis presents with many of the same symptoms of neurodermatitis. It is a contact dermatitis—a type 4 hypersensitivity reaction—less commonly seen than irritant contact dermatitis.4 It results from two phases: the initial induction phase in which the allergen is picked up by dendrites and presented to the T cells; and the elicitation phase in which the previously stimulated T cells respond by releasing large quantities of cytokines.5 The condition typically presents as a rash or lesion that may itch, ooze, crust, or develop scales.3 If the allergen is present chronically, the skin may even darken and thicken. This dermatitis is distinguishable from the irritant form by being more widespread and by being reproducible upon exposure to the allergen. Diagnosis is commonly made by history and physical examination, but a patch allergy test is often definitive.3

Scabies
Scabies is a skin disorder caused by tiny mites known as the itch mite (or Sarcoptes scabiei), and the initial symptoms can mimic neurodermatitis.4 This mimicry can be particularly apparent when patients present with suspicion of mites in their house and on their person. Scabies affects both sexes and all ages, but it is particularly common in nursing homes and child daycare facilities because of the high rate of skin-to-skin contact.3,8         

Scabies is caused by mites that burrow into the skin and lay eggs.5 A portion of the damage done to the skin is from the patient scratching to relieve the itch caused by the burrows. These lesions caused by scratching can appear similar to initial lesions in neurodermatitis; however, a diagnosis of scabies can be accomplished by direct skin examination and microscopic examination for presence of mites, and/or biopsy.3 A biopsy of suspected mite burrows would show inflammatory cell infiltrates comprising eosinophilis, lymphocytes, and histiocytes.9 

Fleas
Whereas the itch mite is roughly the size of a grain of salt, with a length of 0.30 mm to 0.45 mm for females and half that size for males,10 fleas are approximately 3 mm to 4 mm in length, making them more easily visible to the naked eye.11 Fleas are most commonly found in homes with pets. Fleas feed on blood, and although they prefer to live in and feed on dogs, cats, and other warm-blooded fury mammals, when their host of choice is not accessible, they will start to bite humans. In such cases, the fleas reside in carpeting and on other textiles and appear as small dark spots on the legs and feet, particularly upon ambulation. Flea bites appear as small, red, circular bumps that are often found in clusters around the waist, ankles, armpits, and in the bend of the elbows and knees.12 These bumps itch and bleed and turn white when pressed.12 Because fleas are easily visible, the problem is easy to diagnose, and biopsy is rarely necessary. Treatment is focused on eliminating the fleas from the home, surrounding environment, and pets using a variety of pesticides, while the bite symptoms are relieved with over-the-counter 1% hydrocortisone cream and/or oral antihistamines.12

Lichen Planus
Lichen planus is a skin disorder that often presents during the fourth decade of life, although recently an increasing number of diagnoses are being made in elderly patients.13 It affects both sexes equally and is often mistaken for other disorders because of its nonspecific symptoms. The etiology of this disorder is unknown, although genetics is thought to play a role due to familial co-occurrence.14 Chronic active hepatitis C is also commonly observed in these patients, leading to the theory that the virus replicates in the skin, causing irritation in genetically susceptible individuals.13,15 The lesions are quite distinctive, appearing purple, papular, pruritic, polyangular, and planar.13 They tend to be between 2 mm and 10 mm and covered by lacy, white striae that signify epidermal thickening.13 Lichen planus can be diagnosed by biopsy, which would show characteristic band-like infiltrate of lymphocytes at the epidermal-dermal junction and damage to the basal cell layer.16

 

Dr. Norman is in private practice in Tampa, FL. He is also associate professor, University of Central Florida School of Medicine, Orlando, and at Nova Southeastern School of Medicine, Davie, FL. Mr. Porteus is a third-year student of osteopathic medicine at Lake Erie College of Osteopathic Medicine, Bradenton, FL.

The authors report no relevant financial relationships.

References

1. KDOQI Clinical practice guidelines for chronic kidney disease: evaluation, classification, and stratification. National Kidney Foundation Website. http://www.kidney.org/professionals/kdoqi/guidelines_ckd/p6_comp_g11.htm. Published 2002. Accessed August 23, 2013.

2. Murray AM. Cognitive impairment in the aging dialysis and chronic kidney disease populations: an occult burden. Adv Chronic Kidney Dis. 2008;15(2):123-132.

3. Burton J, Holden C. Eczema, lichenification, and prurigo. In: Burns T, Breathnach S, Cox N, Griffiths C, eds. Textbook of Dermatology. Vol 1. 6th ed. Oxford: Blackwell Scientific Inc; 1998:644-645.

4. Kumar V, Abbas AK, Fausto N, Aster J. Robbins and Cotran Pathologic Basis of Disease. 8th ed. Philadelphia, PA: Saunders, 2010:1190-1193.

5. Fried RG, Fried S. Picking apart the picker: a clinician’s guide for management of the patient presenting with excoriations. Cutis. 2003;71(4):291-298.

6. Martin-Bufao R, Ulnik JC, Brufau Redondo C, Corbalan Berna F-J. Personality in patients with psoriasis. In: Soung J, Koo B. Psoriasis. InTech. 2012:209-226. http://www.intechopen.com/books/psoriasis/personality-and-psoriasis. Accessed September 12, 2013.

7. Mayo Clinic Staff. Neurodermatitis. Mayo Clinic Website. www.mayoclinic.com/health/neurodermatitis/DS00712. Published October 2, 2012. Accessed August 23, 2013.

8. Georgia scabies manual. Georgia Department of Public Health Website. http://health.state.ga.us/pdfs/epi/zvbd/Georgia%20Scabies%20Handbook.pdf. Revised February 22, 2008. Accessed August 23, 2013.

9. Walton SF, Currie BJ. Problems in diagnosing scabies, a global disease in human and animal populations. Clin Microbiol Rev. 2007;20(2):268-279.

10. Centers for Disease Control and Prevention Center for Global Health. Parasites and Health. Scabies. http://www.dpd.cdc.gov/dpdx/HTML/Scabies.htm. Accessed September 3, 2013.

11. Centers for Disease Control and Prevention Center for Global Health. Parasite Image Library. Fleas. http://www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/Fleas_il.htm. Accessed September 3, 2013.

12. Medline Plus. Fleas. http://www.nlm.nih.gov/medlineplus/ency/article/001329.htm. Accessed September 3, 2013.

13. Ramos-E-Silva M, Lima CM, Schechtman RC, Trope BM, Carneiro S. Superficial mycoses in immunodepressed patients (AIDS). Clin Dermatol. 2010;28(2):217-225. 

14. Hafez M, Sharaf L, Seafan FA. The inheritance of susceptibility to lichen planus. Indian J Dermatol. 2006;51(1):73.

15. Sánchez-Pérez J, De Castro M, Buezo GF, Fernandez-Herrera J, Borque MJ, García-Díez A. Lichen planus and hepatitis C virus: prevalence and clinical presentation of patients with lichen planus and hepatitis C virus infection. Br J Dermatol. 1996;134(4):715-719.

16. Katta R. Lichen planus. Am Fam Physician. 2000;61(11):3319-3324.