Pityriasis Lichenoides



Pityriasis Lichenoides


Julie E. Jackson, MD

Chandra N. Smart, MD





Key Facts


Terminology



  • PLEVA



    • Mucha-Habermann disease, febrile ulceronecrotic Mucha-Habermann disease


    • Recurrent crops of erythematous papules of unknown etiology favoring children or young adults and spontaneously resolving over weeks


  • PLC



    • Guttate parapsoriasis


    • Chronic form of PLEVA also typically affecting children but can affect any age; predominantly truncal rash persists for years


Microscopic Pathology



  • PLEVA



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


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


  • PLC



    • Blunted features of PLEVA seen


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


    • No atypical lymphocytes in either entity







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

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

Full access? Get Clinical Tree
Get Clinical Tree app for offline access