A Child With Persistent White Spots on His Upper Body

An 11 year-old boy presented to clinic for a sick visit with complaints of white spots on his chest, abdomen, and back. They were not pruritic, and no family members or friends had a similar rash. The boy’s father said that the lesions had been present for about 2 years.  The boy had been initially diagnosed with tinea versicolor 2 years ago and treated with topical ketoconazole and triamcinolone without noticeable improvement. His physical examination results showed numerous oval, 0.5 cm hypopigmented macules with fine scaling, including some erythematous papules, scattered over his chest, abdomen, and back (Figures 1 and 2).  

What was the cause of the child’s symptoms?

Answer: Pityriasis lichenoides chronica

DISCUSSION

The boy was referred to dermatology and was diagnosed as having pityriasis lichenoides chronica, a rare inflammatory skin disorder considered to be a subtype of pityriasis lichenoides.¹ It is characterized by the gradual development of erythematous t brown macules and papules with fine, centrally-attached scale, usually on the trunk, buttocks, and proximal extremities. Patients are otherwise asymptomatic, although some have pruritus. The disease follows a relapsing and remitting course, with complete resolution over several months to years.²

The few studies on pityriasis lichenoides chronica rarely differentiate pityriasis lichenoides chronica from other types of pityriasis lichenoides.² Therefore, the incidence is unknown, and no associations with sex, race, or ethnicity have been confirmed. Some have reported peak incidences at ages 6 and 10 years.³ Theories about the pathogenesis of pityriasis lichenoides chronica include inflammatory response to infectious agents, inflammatory response to T-cell dyscrasia, or secondary to immune complex-mediated hypersensitivity vasculitis.¹ However, there is no consensus on the pathophysiology of the condition.⁴

The differential diagnosis for pityriasis lichenoides chronica is wide, and final diagnosis is based on clinical suspicion and biopsy. Characteristic findings on histologic examination include: parakeratosis, mild spongiosis, minimal lymphocyte exocytosis, minimal vacuolar change, focal necrotic keratinocytes at the dermoepidermal junction, perivascular and lichenoid lymphohistiocytic infiltrate in the superficial dermis, and extravasated erythrocytes in the papillary dermis.² 

No explicit treatment is indicated, as pityriasis lichenoides chronica is benign and nonscarring.² However, it may be prudent to pursue treatment in order to decrease both the visible signs of disease and the associated pruritis. Anti-inflammatory agents are the treatment of choice. First-line therapies include topical corticosteroids, tetracycline, and erythromycin. Second-line therapies include UV-B or psoralen plus UV light therapy. Additional therapies include topical tacrolimus, methotrexate, and other systemic immunomodulators; the use of these therapies is guarded because of their adverse effect profile.¹ Our patient was was started on erythromycin after the diagnosis, and ketoconazole and triamcinolone were discontinued. It is important to note that pityriasis lichenoides chronica has rarely been associated with the development of cutaneous lymphomas, but it is suggested that patients with pityriasis lichenoides chronica have an annual head-to-toe skin examination as a precaution.² 

Y-vu Robert Van, BA, Nourhan Ismaeel, BS, and Lynette Mazur, MD, MPH, are with the University of Texas Health Science Center at Houston.

References

1.     Bowers S, Warshaw EM. Pityriasis lichenoides and its subtypes. J Am Acad Dermatol. 2006;55(4):557-576.

2.     Musiek A. Pityriasis lichenoides chronica. UpToDate. http://www.uptodate.com/contents/pityriasis-lichenoides-chronica. Updated August 16, 2016. Accessed November 2, 2016.

3.     Geller L, Antonov NK, Lauren CT, Morel KD, Garzon MC. Pityriasis lichenoides in childhood: review of clinical presentation and treatment options. Pediatr Dermatol. 2015;32(5):579-592.

4.     Khachemoune A, Blyumin ML. Pityriasis lichenoides. Am J Clin Dermatol. 2007;8(1):29-36.