Pediculid: Literature Review with Case Presentation

Abstract

Introduction

ID reactions are infrequent disorders which are often misdiagnosed because they developed as acute dermatitis after days or weeks at skin locations distant from the initial inflammatory or infectious/infestations site. For now, several causes have been described to trigger such reactions which includes infection with dermatophytosis, Mycobacterium, viruses, bacteria, and parasites. Pediculid nowadays is forgotten entity in dermatology daily practice as well as major dermatology textbooks.

Case Presentation

We present an illustrative case report of pediculid that is an ID reaction to Pediculosis capitis in 6 y.o. girl with acute generalized eczematous dermatitis successfully treated by elimination of pediculosis. Also, there is description of relapsing the condition with reinfestation.

Discussion/Conclusion

During discussion and literature review, comprehensive description was made to the ID reaction as entity and its diagnostic criteria. In conclusion, we want to highlight that being aware of such possibility is important (especially in pediatric patients) to reach a correct diagnosis quickly and avoid unnecessary treatment and examinations.

Established Facts

• There are existing ID reactions described for different causes such as insect bites and bacterial or fungal infections. However, ID reaction to parasites is usually underrecognized.

Novel Insights

• Sudden eczematous eruption in a child without any history of scalp symptoms may point to ID reaction.

• Scalp examination is mandatory for sudden eczema in pediatric group.

• Pediculid is known but forgotten entity even in major dermatological textbooks.

Case Presentation

A 6-year-old girl came to our clinic with generalized eczematous rash developed 2 weeks ago with progressive course. On examination, polymorphic disseminated itchy rash was found, consisting of groups of erythematous papules, vesicles, and eczematous plaques with purplish and bluish-grey shadows along with dusky-red erythema and fine white scales on the trunk (including dorsal part), upper and lower limbs (shown in Fig. 1). In addition, old slightly hyperpigmented patches and enlarged cervical lymph nodes were detected. According to her parents' report, she did not receive any medication during the last few weeks except some ibuprofen for fever.

Fig. 1.

a, bInitial manifestation of the disease.

Surprisingly, scalp examination revealed massive infestation with Pediculus humanus capitis including adult louse and nits. Feeding adult louse (shown in Fig. 2a) was filmed and residuals from newly hatched nymphs after molting (shown in Fig. 2b) pictured under dermoscopic examination (Polarized DL4, x10). Some impetiginized lesions on scalp were found as well.

Fig. 2.

Feeding adult louse (a), residual chitin cover after nymph moulting (b), and nits (c).

The diagnosis of pediculid was made according to the clinical picture and findings described above, history, and examination of clothes to exclude co-infestation with Pediculus humanus corporis.

Our treatment prescription included potassium permanganate solution as wet dressing for impetiginized scalp lesions and for the same treatment purposes systemic antibiotic therapy with amoxicillin/clavulanic acid with general dosing according to age and weight was prescribed in addition to Cetirizine as an antihistamine to relieve itching. Main treatment was oriented to eliminate head louse infestation − ivermectin 1% lotion along with manual nits elimination by a special hair combing technique.

On follow-up examination after 2 weeks, full resolution of skin lesions was detected apart from few spots of postinflammatory hyperpigmentation (shown in Fig. 3). Head louse infestation was eliminated, but additional prophylactic treatment with ivermectin lotion was recommended for further 2 weeks one time per week. Unfortunately, the patient did not comply with final prophylactic treatment and got reinfestation (shown in Fig. 4) with same manifestation of ID reaction back. Finally, the patient was successfully treated by only ivermectin 1% lotion to eliminate the pediculosis completely.

Fig. 3.

a, bFollow-up examination status.

Fig. 4.

a, bReappearance of lesions.

Discussion

ID reaction refers to an immunologic reaction to the causative agent (infection or infestation) that may manifest as a dermatitic rash at the skin location distant from primary localization of the causative agent. Reporting of generalized reaction to pediculosis has long history since 1945 but actually not many publications can be found in worldwide depository. In our opinion, this type of disorder is undeservedly poorly described in old and modern dermatological textbooks. Most of famous textbooks either give just a term “per se” or not mention it at all.

The first case report was done in 1945 by Morris [1], but the case described in that clinical note to the New England Journal of Medicine was about pediculosis corporis in which dermatitis was caused by the biting pediculi. Anyhow, the attention was paid and emphasized by following paper to the same journal in following year with case series report of 3 cases with “all over the body dermatitis” caused by P. capitis in which the correct diagnosis had been initially missed. Ronchese [2] in his article concluded that in P. capitis, besides a dermatitis limited to scalp and neck, doctors must keep in mind that generalized dermatitis (which hard to interpret) might be present. Dermatitis in such cases is self-inflicted, resulting from a neurogenic pruritus originating in the skin of the scalp. By an alternative theory, allergen containing in biting louse saliva is carried directly from the scalp to the body skin by the patient's nails. By one mean or another, treatment must be thorough since as long as a single nit is present, the dermatitis of the scalp, neck, and body will continue.

After that, few different publications have been made including bullous eruption due to pediculosis pubis, falsely diagnosed as pemphigus vulgaris [3]. This was the first publication including biopsy, which was falsely interpreted as pemphigus vulgaris by the general pathologist. Further re-evaluation with a dermatopathologist pointed away this diagnosis, as well as the possibility that lesion was result of the bite itself and suggested papular urticaria-like reaction in response similar to such in an arthropod bite.

The term “pediculid” was proposed by Brenner and coauthors in 1984 in their case series report [4]. In the same article, authors describe the criteria by which diagnosis of pediculid can be made:

1. True ID reaction includes a group of secondary lesions that cannot be identified as one of common dermatitis.

2. Sudden onset.

3. Developing rash is generalized involving trunk, arms, and legs.

4. There is no evidence of direct external contactant or infective agent.

The most recent related publication we found during work on this article was a 2012 case report of autosensitization dermatitis caused by P. capitis written by Takçi and coauthors [5] about a 72 y.o. female patient. The rash she had was pale erythematous maculo-papular patches with linear excoriations due to severe pruritus. Mobile cervical lymphadenopathy was noted as well. Described findings were previously misdiagnosed by other doctors (duration of disease was about 6 months) as atopic dermatitis, Bullous pemphigoid, and Duhring's disease. While the histopathological examination reveals spongiotic dermatitis, no immune deposition was identified in the immunofluorescent analysis. The patient was completely treated with 1% permethrin hair lotion for P. capitis.

There are reported cases of double infestation of head and body lice − this point dictated the investigation of our patient clothes because bluish-grey color of some lesions can point to maculae cerulea − feeding point of body lice. Some authors describe turning these two types of lice to one another if they cannot reach their usual habitat due to their genetic similarities [6]. Both of these causes were excluded in our case.

There are no epidemiological studies of prevalence of such disorder, but probably, it reaches about 4–5% of all patients with P. capitis [4]. Thus, exclusion infection or infestation focus in patients who present with sudden generalized pruritic maculopapular eruption is important, before considering any complicated diagnosis requiring conduction of more sophisticated investigations.

Conclusion

Pediculid nowadays is a forgotten entity in dermatology daily practice. Clinical and histopathological manifestations of pediculid as an ID reaction to P. capitis infestation are variable. They include erythematous, maculopapular generalized rash, bullous or eczematous lesions which may have purplish and bluish shadows besides erythema and may mimic the rash of viral exanthem. Symptoms often include fever, anorexia, and lymphadenopathy. So, being aware of such possibility is important (especially in pediatric patients) to reach a correct diagnosis quickly and avoid unnecessary investigations.

Statement of Ethics

Ethics approval not required according to local guidelines (Al-Azhar University Ethics Committee). Written informed consent was obtained from parents for publication of the details of this medical case and any accompanying images.

Conflict of Interest Statement

The author has no conflicts of interest to declare.

Funding Sources

The author did not receive any funds.

Author Contributions

The single author performed all the work.

Data Availability Statement

The author is ready to provide any existing additional data upon request.