Pityriasis Lichenoides



Pityriasis Lichenoides


Julie E. Jackson, MD

Chandra N. Smart, MD










PLEVA consists of scattered crusted necrotic erythematous papules image located on the trunk and extremities. (Courtesy K. Suh, MD.)






PLEVA at low power demonstrates a wedge-shaped lymphocytic infiltrate extending to the deep papillary dermis along with the obscured dermal epidermal junction due to interface change.


TERMINOLOGY


Synonyms



  • Pityriasis lichenoides et varioliformis acuta (PLEVA), Mucha-Habermann disease, febrile ulceronecrotic Mucha-Habermann disease


  • Pityriasis lichenoides chronica (PLC), guttate parapsoriasis


ETIOLOGY/PATHOGENESIS


Unknown



  • Proposed hypersensitivity reaction to viruses, possible autoimmune association (rheumatoid arthritis, hypothyroidism, pernicious anemia), or drug induced


CLINICAL ISSUES


Presentation



  • PLEVA



    • More common in children with male predominance; asymptomatic recurrent crops of crusted erythematous papules or vesicles that self resolve over a period of weeks


    • In acute febrile ulceronecrotic variant, constitutional symptoms such as fever, malaise, arthritis, and lymphadenopathy are also present


    • Those with diffuse skin lesions appear to have shorter course than patients with peripheral skin lesions


  • PLC



    • Any age group can be affected but often seen in children as red brown papules with characteristic scale that slowly regress over months


    • Can take on a chronic relapsing course with prolonged periods of remission in between flares


Treatment



  • First line with topical corticosteroids, topical coal tar, phototherapy, antihistamines, or oral tetracycline or erythromycin for anti-inflammatory effects


  • Treat systemic symptoms with systemic corticosteroids and refractory cases with weekly methotrexate


Prognosis



  • PLEVA: Self resolving over weeks


  • Acute febrile ulceronecrotic PLEVA: Usually lasts several months with relapsing disease and eventually converts into classic PLEVA; rare reports of death typically in adult cases


  • PLC: Chronic relapsing course over months with eventual tendency for self resolution, though rare cases of progression to cutaneous T-cell lymphoma have been reported


MICROSCOPIC PATHOLOGY


Histologic Features



  • PLEVA



    • Superficial perivascular brisk lymphocytic infiltrate with interface change at dermal-epidermal junction; infiltrate extends into reticular dermis in wedge-shaped fashion


    • Prominent lymphocyte exocytosis with intraepidermal red blood cells


    • Epidermis with overlying crust, foci of parakeratosis, acanthosis, and basal layer vacuolar change


    • Depending on extent of infiltrate, edema and epidermal necrosis may also be present along with extravasation of red blood cells and lymphocytic vasculopathy


  • PLC



    • Blunted features of PLEVA are seen


    • Parakeratosis with less lymphocytic infiltrate in dermis and less interface change at dermal-epidermal
      junction with focal apoptotic keratinocytes


    • Perivascular lymphocytic inflammation in superficial dermis ± extravasation of red blood cells


    • No atypical lymphocytes in either entity


DIFFERENTIAL DIAGNOSIS


Lymphomatoid Papulosis



  • Self-healing benign eruption with malignant-appearing histology


  • Dense atypical lymphocytic infiltrate distributed in wedge-shaped, lichenoid pattern or large cell variant often with overlying crust and necrotic keratinocytes


Drug Eruption



  • Wedge-shaped dermal lymphohistiocytic infiltrate with conspicuous eosinophils distinguishing this entity from PLEVA


Arthropod Reactions



  • Histologic spectrum, but classically wedge-shaped mixed dermal infiltrate with eosinophils, overlying epidermal spongiosis, crust, and occasional identifiable insect mouth parts


Guttate Psoriasis

Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Pityriasis Lichenoides
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