Peer Reviewed

What's Your Diagnosis?

What Is the Cause of This Boy’s Asymptomatic Papular Rash?

Alexander K. C. Leung, MD; Benjamin Barankin, MD; and Kin Fon Leong, MD

Alexander K. C. Leung, MD; Benjamin Barankin, MD; and Kin Fon Leong, MD

Leung AKC, Barankin B, Leong KF. What is the cause of this boy’s asymptomatic papular rash? Consultant. 2018;58(1):17-19.


A 5-year-old boy presented with an asymptomatic rash on the trunk and extremities of approximately 8 months’ duration. The child was otherwise healthy and was not on medications. His past health was unremarkable. There was no family history of similar skin lesions.

Physical examination revealed multiple, small, scaly, erythematous to reddish brown papules on the trunk (Figure 1) and extremities (Figure 2). The papules varied from 1 to 4 mm in diameter. Some of the lesions showed thin, superficial, micaceous scales (Figure 3). The lesions were at different stages of development. There was no mucosal or ungual involvement. The rest of the physical examination findings were unremarkable.

Pityriasis lichenoides chronica

Pityriasis lichenoides chronica

Pityriasis lichenoides chronica

What’s Your Diagnosis?

  1. Pityriasis lichenoides chronica
  2. Lichen planus
  3. Impetigo
  4. Tinea corporis

Answer on next page.

Answer: Pityriasis lichenoides chronica

A clinical diagnosis of pityriasis lichenoides chronica (PLC) was made. Histologic results of a skin biopsy revealed hyperkeratosis and parakeratosis in the epidermis and extravasation of erythrocytes, basal vacuolar degeneration, and perivascular lymphocytic infiltrates in the papillary dermis. These findings were in keeping with a diagnosis of PLC.

The boy’s parents were reassured about the benign nature of the condition. Various treatment options were discussed with the parents. They opted for watchful observation, since the lesions were asymptomatic. At the boy’s 6-month follow-up visit, multiple hypopigmented macules were seen at the site of previous lesions (Figure 4).

Pityriasis lichenoides chronica


PLC is a papulosquamous disease characterized by the gradual development of asymptomatic, erythematous to reddish brown, scaly papules that spontaneously resolve over a period of weeks to months, often with residual hypopigmentation or hyperpigmentation.1,2


Data on the prevalence and incidence of PLC are lacking, since the literature on this condition is limited to case reports and case series. The condition is most frequently seen in children and young adults with a peak age of 5 to 10 years.3 Presentation before the age of 2 years is unusual.4 Very rarely, PLC occurs in the first year of life or even at birth.5 The condition is slightly more common in males.1,3 There is no predominance based on ethnicity or geographic location.6


The exact pathogenesis of PLC is not known. Some authors believe that the condition represents an inflammatory response to an infectious agent (eg, Epstein-Barr virus; varicella-zoster virus; parvovirus B19; adenovirus; herpes viruses 2, 6, and 7; cytomegalovirus, HIV; Staphylococcus aureus; Streptococcus pyogenes; Mycoplasma species; Toxoplasma gondii).3,6-8 The condition also has been reported to have developed following the administration of vaccinations for influenza, hepatitis B, and measles, mumps, and rubella.3,9

Other authors believe that PLC is an inflammatory response to an underlying T-cell dyscrasia or that the condition is secondary to an immune complex-mediated hypersensitivity vasculitis.6,7 Occasionally, PLC may develop in association with recent exposure to medications (eg, acetaminophen, adalimumab, etanercept, infliximab, pembrolizumab, and statins).10-15 The mechanisms through which medications might induce PLC are not known.


Histopathologic examination of the rash shows parakeratosis, perivascular and lichenoid lymphohistiocytic infiltrates in the superficial dermis, mild vacuolar changes at the dermoepidermal junction, extravasation of erythrocytes in the papillary dermis, and an interface dermatitis.1,3


Typically, PLC presents with recurrent crops of polymorphic, erythematous to reddish brown maculopapules.6 The onset of maculopapules is often gradual.3 There is usually a fine micaceous adherent scale, likened to frosted glass, attached to the center of the lesion, which can be scraped off to reveal a shiny, pinkish brown surface.3 Lesions tend to wax and wane.3 Affected patients are often asymptomatic, although some patients experience pruritus.3 Typically, the papules spontaneously flatten and regress over a period of weeks to months, often with residual dyspigmentation.1,6 Lesions in different stages of development may be seen. Sites of predilection include the trunk, buttocks, and extremities.6 Involvement of the head and acral areas, while uncommon, also has been reported.6,16 Ocular and oral involvement have rarely been described.3


The diagnosis is based on a classic clinical picture and is usually confirmed by way of a skin biopsy. The diagnosis can also be aided by dermoscopy. Typically dermoscopic findings include orange-yellowish, structureless areas, nondotted vessels (including milky area/globules, linear irregular vessels, and linear branching vessels), and focally distributed dotted vessels.17


The differential diagnosis includes pityriasis lichenoides et varioliformis acuta, lichen planus, drug eruption, pityriasis rosea, guttate psoriasis, insect bites, generalized folliculitis, chickenpox, impetigo, disseminated herpes zoster, vasculitis, postinflammatory dyspigmentation, tinea corporis, Gianotti-Crosti syndrome, hypopigmented mycosis fungoides, lymphomatoid papulosis, and secondary syphilis.6,8,18


PLC can be disfiguring and socially embarrassing. There is usually no residual scarring. However, hypopigmented or, less commonly, hyperpigmented macules may result at sites of prior lesions.1,3 The possibility of malignant transformation to cutaneous T-cell lymphoma is controversial.3,4


The disease runs a relapsing and remitting course that may persist for months to years.3


Because the condition is benign and self-limited, treatment might not be necessary. For patients who desire treatment for cosmetic purposes or who have symptomatic disease, topical corticosteroids and oral antibiotics (erythromycin for children and tetracyclines for adults) are the treatment of choice.1,19 Other treatment options include topical calcineurin inhibitors (eg, tacrolimus, pimecrolimus), UV-B, psoralen plus UV-A phototherapy, and, uncommonly, systemic immunosuppressants (eg, glucocorticoids, methotrexate, cyclosporine).2,4,13,20 For resistant lesions, a combination of therapies may be necessary. 

Alexander K. C. Leung, MD, is clinical professor of pediatrics at the University of Calgary and a pediatric consultant at the Alberta Children’s Hospital in Calgary, Alberta, Canada.

Benjamin Barankin, MD, is a dermatologist and the medical director and founder of the Toronto Dermatology Centre in Toronto, Ontario, Canada.

Kin Fon Leong, MD, is a consultant pediatric dermatologist at the Pediatric Institute, Kuala Lumpur General Hospital, in Kuala Lumpur, Malaysia.



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