Dermatology Clinic CASE
Red Bumps on Arms and Legs DINA ZAMIL, BS;TARA L. BRAUN, MD; CHRISTOPHER RIZK, MD
A 6-year-old girl presents with a 1-year history of a waxing and waning rash on her limbs and face.The rash starts as red scaly bumps that fade over several weeks leaving smooth white spots. Every few months, the patient gets several new red bumps.The rash is not itchy or painful. Her parents have tried topical steroid creams that did not help clear the rash. Examination reveals scattered erythematous scaly papules on both legs and several hypopigmented macules on her legs, arms, and face.
DIAGNOSIS
Pityriasis Lichenoides Chronica
Pityriasis lichenoides (PL) describes a spectrum of acute and chronic dermatoses that includes pityriasis lichenoides et varioliformis acuta (PLEVA) and pityriasis lichenoides chronica (PLC).1,2 The chronic form, PLC, is characterized by scaly red to brown papules that resolve spontaneously and recur frequently.1,2 In 1894, the chronic and acute forms of PL were first described by Jadassohn and Neisser, respectively, in separate case reports.3-5 The term pityriasis lichenoides chronica was first used in 1899 by Juliusberg.3,6 The acute form of PL was distinguished from PLC in 1916 by Mucha7 and was named pityriasis lichenoides et varioliformis acuta in 1925 by Habermann.3,7 The prevalence of PL in the general population is estimated to be 0.05%.1 It is slightly more common in men and occurs more frequently in late childhood or early adulthood, but can occur at any age.3 Pityriasis lichenoides has been reported across many ethnic groups and geographic locations with no racial predilection.1,3,8 The PLC subtype occurs more frequently than PLEVA and tends to affect children.1,3,8 One study found that Black patients were more likely to develop PLC and White patients were more likely to develop PLEVA.9
Although the exact etiology and pathogenesis of PL are not understood fully, 3 theories predominate.8 The first theory is that PL is an inflammatory reaction to an antigenic agent. Infections and drugs have been linked to cases of PL.3,8 An infectious etiology is supported by several characteristics of PL such as familial outbreaks, young age of onset, and acute eruptions. Infectious PL cases have been linked to Toxoplasma gondii, Epstein-Barr virus, and HIV.3 The second theory is that PL is a lymphoproliferative disorder.This theory is supported by reported cases of PLC progressing to mycosis fungoides.8 The third major etiologic theory states that PL is an immune-complex–mediated hypersensitivity vasculitis.3,8 Studies have found immunoglobin deposits in biopsies of PL lesions and circulating immune complexes in some patients with PL.8 PLC typically presents with gradually developing lesions on the proximal extremities and trunk.The lesions are small, erythematous or brown, and have centrally attached fine parakeratotic scales.2,8 When removed, these scales may leave a shiny brown or pink macule.8 The lesions generally do not scar but leave areas of hyper- or hypopigmentation. Patients with PLC may experience periods of remission between outbreaks.1,2
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