A 9-year-old boy, who has no significantmedical history, presents with a generalizedpruritic eruption of 2 weeks’ duration.One week earlier, another practitionerruled out scabies and treatedhim presumptively for varicella.
A 9-year-old boy, who has no significantmedical history, presents with a generalizedpruritic eruption of 2 weeks' duration.One week earlier, another practitionerruled out scabies and treatedhim presumptively for varicella.The patient is in no acute distress,does not appear to be ill, and has nofever, chills, malaise, or upper respiratorytract symptoms. Multiple, excoriatedand intact, uniformly sized, firm,tan papulovesicles are generally distributedon the trunk, upper and lowerextremities, and neck. Many of the papulesfeature necrotic tops (Figure 1).A punch biopsy of the left flankreveals an interface dermatitis, vacuolartype, with a superficial and deepwedge-shaped perivascular lymphocyticinfiltrate. Scattered extravasated erythrocytesare seen in the superficial dermis;numerous dyskeratotic keratinocytesand focal epidermal necrosis arenoted. Foci of scale crust are present inthe cornified layer. Pityriasis lichenoideset varioliformis acuta (PLEVA) isdiagnosed.Erythromycin ethylsuccinate suspension,40 mg/kg/d in 3 divideddoses, is prescribed. Thirty days later,multiple hypopigmented macules arepresent in all of the previously involvedareas. There are no new lesions. Somecrusted papules and several postinflammatory lesions with a fine, slightlymicaceous scale are noted (Figure 2).Antibiotic therapy will be continueduntil all lesions resolve.CLINICAL FEATURES
Pityriasis lichenoides was firstdocumented in the late 1800s. 1 Sincethen, several variants have beendescribed based on morphologic differencesand disease progression.These include PLEVA, or febrileulceronecrotic Mucha-Habermanndisease, and pityriasis lichenoideschronica (PLC).1The acute form, PLEVA, is a selflimiteddisease characterized by cropsof discrete erythematous papulesthat evolve into vesicles, pustules, andcrusted ulcers, which may heal withvarioliform scarring and residual hypopigmentation.2-4 Lesions are commonlylocated on the trunk and proximalextremities; the face, palms, andsoles are rarely involved. 5 In children, the scalp and mucous membranes areseldom, if ever, affected. 6 PLC, the most common variant,is characterized by reddish brownmacules with an adherent centralscale that tends to separate spontaneouslyfrom the underlyinglesions. 3,7 PLC lesions do not vesiculateand do not form scars. Patientsmay present with either PLEVA orPLC lesions or with a combination ofPLEVA and PLC lesions.CAUSES
The cause of PLEVA is unknown;however, a hypersensitivity reactionto an infectious organism is suspectedbecause of the development oflocalized outbreaks.8 Although variousinfections have been documentedin patients with PLEVA, no organismhas been shown to be directly responsible,9 and person-to-person transmissionhas not been reported.7,10No racial or geographic predilectionhas been documented. Generallyconsidered a disease of adolescence,PLEVA has been diagnosed in neonatesand in elderly persons5; boysand men are affected slightly moreoften than girls and women.DIAGNOSIS
PLEVA is commonly misdiagnosedbecause it resembles a numberof other diseases. Since consistentlaboratory abnormalities have notbeen identified, the diagnosis ofPLEVA is based on clinical appearanceand histologic findings. 5,7 Thehistopathologic changes found in thispatient and described above are typicalof the disease. Extravasation andtransepidermal elimination of erythrocytesis also a common feature. 11 Correlation of clinical and histologicevidence is crucial because microscopicfindings can be nonspecificand may vary based on the evolutionarystage of the biopsy specimen. 2 The morphology and distributionof PLEVA lesions may resemblethe manifestations of other diseases,such as arthropod bites, lymphomatoidpapulosis, Gianotti-Crosti syndrome,and secondary syphilis. Particularlyin children, PLEVA can beconfused with varicella, or chickenpox. 4-7,11,12 Both PLEVA and varicellamanifest as discrete papules thatprogress to vesicles, then to crustedand hemorrhagic lesions, and finallyto hypopigmented areas or scars. Inaddition, PLEVA and varicella eruptionsboth feature lesions that are atvarious stages of development.Some important features can aidin differentiating the 2 conditions.Most patients with PLEVA are otherwiseasymptomatic, whereas personswith chickenpox experience constitutionalsymptoms. A Tzanck preparationobtained from the base of a varicellavesicle will show multinucleatedgiant cells with ballooning degenerationof keratinocyte nuclei; a PLEVAlesion specimen will not display thesecytopathologic changes. The characteristicsthat help distinguish the 2diseases are listed in the Table.COURSE
Patients with PLEVA experienceno systemic illness; individual lesionsare usually asymptomatic but mayburn or itch. 13Staphylococcus aureusis the most common cause of secondaryinfections.13 The diseasewaxes and wanes over a few weeks tomonths and then resolves spontaneously.7 In rare cases, PLEVA mayendure for years. Recurrences arenot uncommon.Classically, patients with PLChave longer-lasting disease with longerrelapses than persons with PLEVA,although it is generally thought thatthe 2 disorders are opposite ends ofthe spectrum of the same diseaseprocess.13 Some experts believe thatthe distinction between the 2 conditionsis inappropriate because acuteand chronic lesions often coexist.3,5,13One study correlated diseasebehavior with lesion distributionrather than with the chronicity of thelesions.3 The researchers found thatthe disease lasted an average of 11.4 months in patients with diffuse lesiondistribution, 17.3 months in those withcentral lesions, and 31.3 months in patientswith peripheral disease. Otherstudies have found this topographicinterpretation to be less significant inpredicting disease outcome. 2PLEVA is considered a benigndisease2; however, a few cases oftransformation into cutaneous T-celllymphoma have been documented.9,14This evidence implies at least a potentialrisk of malignancy. 9,14MANAGEMENT
The variable nature of this diseasehas led to the use of manymodalities.2 Topical corticosteroidsand oral antihistamines may relievethe pruritus, but these agents have littleif any effect on the overall courseof the disease.5 Phototherapy withpsoralen-UV-A (PUVA), UV-A, andUV-B has been very effective in clearinglesions in adults.7 Tetracyclines,erythromycin, dapsone, methotrexate,and pentoxifylline have been effectivein some patients.7,10The treatment of choice forchildren is erythromycin, 30 to50 mg/kg/d.5,10 A slowly tapereddosage over several months clearslesions faster than if they were leftuntreated, and such therapy prolongsremissions in children. Rapid withdrawalof the drug may cause a relapse.10 While the exact mechanismof action of erythromycin in thissetting is not known, the inhibition ofmonocyte chemotaxis is thought tobe responsible for its anti-inflammatoryeffect.5Although the long-term sequelaeassociated with phototherapy inchildren are largely unknown, considerthis modality for those who fail torespond to erythromycin.15
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