An otherwise healthy 14-year-old female presents to your
office for a rash on her nose that has not improved with traditional acne
therapies. The patient reports having had acne on her face for about 2 years
now. She had initially been treated with a topical retinoid. This helped with
the comedones on her forehead, cheeks and chin, but the inflammatory papules
and pustules on her nose have continued to slowly progress. After completing a
2-month oral course of doxycycline with no improvement, she was referred for
Andrew C. Krakowski
The patient seems sociable and at ease. She reports good
adherence to her past acne treatment plans and denies any unusual picking or
manipulation behaviors. She has no known allergies and takes no other
medications. She has never been sexually active, and she denies a history of
recurrent illnesses. She has never traveled outside of the United States, and
she lives in an apartment building with the rest of her unaffected family
members. Her only known exposure to animals is through her aunt, who works at a
plant that specializes in the smoking and salting of fish.
Physical exam shows a healthy-appearing female with a
follicular-based, inflammatory popular and pustular eruption concentrated at
the middle of her face, localizing mainly to her nose. No comedones — open
or closed — are present on her skin. There is no evidence of blepharitis
or alopecia. The remainder of her skin exam is remarkable only for how
unremarkable it is. She has no lymphadenopathy. Her physical exam is otherwise
Figure 1. Figure 1 is a patient with atypical pustuler eruption of the nose.
You decide to perform bacterial, fungal and atypical
mycobacterial cultures of the pustules and treat her empirically with a 2-month
oral course of trimethoprim-sulfamethoxazole. When she returns to your office
for follow-up, her cultures are all negative, and the pustules have not
diminished. In fact, both she and you feel her condition may have worsened
Based on these findings, you begin to widen your
differential diagnosis. Which of the following management options would most
likely help you to elucidate the true pathogenesis of this patient’s
atypical pustular eruption of the nose?
A.Try an empirical 2-month course of oral cephalexin.
B.Perform a skin scraping and plate the contents on a
glass slide for microscopic exam.
C.Carefully un-roof a pustule and send the contents for
direct fluorescent antibody (DFA) and viral culture.
D.Pay a visit to the aunt’s factory and find out
what is so fishy about this story.
The patient presents with an atypical pustular eruption
of the nose and central face that is culture negative and unresponsive to oral
antibiotics. An empirical course of cephalexin, as suggested by answer A, would
not be expected to improve the patient’s condition any more so than the
already attempted doxycycline and TMP-SMX; likewise, empirical treatment gets
you no closer to the true pathogenesis of her condition. Answer C offers two
methods commonly employed for diagnosing herpes virus infection. Nothing about
this patient suggests a herpetic etiology, but it would probably not hurt to
send a viral culture as part of her larger workup. Alas, those specific tests
would have been negative, as well. Visiting the aunt’s fish factory, as
recommended by answer D, would only yield an abundance of red (ie, smoked and
salted) Atlantic herrings.
That leaves answer B. You carefully un-roof several of
the patient’s pustules with a 15-blade and scrape the skin, plating the
contents on a standard glass slide. Microscopy reveals an organism with a
flattened head, elongated abdomen and four pairs of short, peg-like legs. You
immediately recognize the distinctive features of Demodex folliculorum,
a vermiform mite that inhabits the lumen of sebaceous follicles, with a
predilection for the larger pilosebaceous units of the nose, forehead, chin and
scalp. The mites are commonly seen as “incidental findings” in
biopsies of older patients. They have also been implicated as a potential cause
(or consequence) of rosacea, although evidence remains controversial. A
different species of Demodex mite (D. canis) causes
demodectic mange in dogs but does not affect humans.
Figures 2 and 3. Figures 2 and 3 are images of Demodex mites, a vermiform mite that inhabits the lumen of sebaceous follicles. The mites are commonly seen as “incidental findings” in biopsies of older patients.
Folliculitis caused by the Demodex mite occurs
most commonly in the setting of immunosuppression (eg, HIV infection,
chemotherapy, leukemia, etc). True infection is extremely uncommon in
prepubertal patients with competent immune systems. The finding of extensive
Demodex mites in this teenage female prompts you to complete a thorough
clinical workup and lab investigation, which thankfully reveals no underlying
With the diagnosis made, you initiate targeted therapy.
You start with topical metronidazole, which is well tolerated by most people,
and the patient begins to respond rapidly. Two weeks later, she has some
persistent erythema and several residual pustules, so you change to topical
permethrin, applied once weekly for an additional 2 weeks straight. At her most
recent follow-up appointment, her lesions have completely cleared with only
some residual post-inflammatory hyperpigmentation.
- Andrew C. Krakowski, MD, completed a residency in pediatrics at Johns Hopkins Medical Institute and a residency in dermatology at University of California, San Diego. He is currently a fellow in pediatric dermatology at Rady Children’s Hospital, San Diego. Catch him on Outdoor Channel as the host of boonDOCS Wilderness & Travel Medicine Show (email:dr.k@boonDOCSmedicine.com). Disclosure: Dr. Krakowski reports no relevant financial disclosures.