1.5.2 Pityriasis Lichenoides

PLEVA: Mucha-Habermann disease.

PLC: Jadassohn Juliusberg disease.

Around 29% show the subtype of pityriasis lichenoides chronica et varioliformis acuta (PLEVA), 67% the subtype pityriasis lichenoides chronica (PLC) and in 4% a mixed type. The prevalence is around 20: 100,000 cases and there are two prevalence peaks in pre- and school-age and around the fifth life decade.

Pityriasis lichenoides is a disease with acute, subacute and chronic course with primarily benign proliferation of helper- and cytotoxic T-cells (reactive and /or inflammatory proliferative disease).

A clear pathogenesis of both subtypes of pityriasis lichenoides is not known. It shows a parainfectious course associated with upper respiratory or gastro-intestinal infections with preferentially Epstein-Barr, HIV-, CMV-, Parvo B19- and Varicella virus. Other infectious microbes reported are stapyloccoci and streptococci or Toxoplasma gondii. In more than 20% of cases in childhood, a post-infectious course can clearly be found. However, similarities with lymphomatoid papulosis have given evidence of a clonal and oligoclonal expansion of CD5/7/30 positive and CD4 dominated cell type in PL. Some evidence exists that in the acute type, the main driving cells are of the cytotoxic T-type. Furthermore, chimeric maternal keratinocytes could be found in biopsy material of the epidermis giving rise of a GVHD like pattern.

Iatrogenic PL eruption has been documented following biologic treatment (tumor necrosis factor α inhibitors (TNF-α)programmed cell death protein 1 (PD-1) inhibitors).

PLEVA: First at the trunk small or 5-10mm red macules, then papulosquamous and papulo-vesicular lesions develop and progress over weeks. Hemorrhagic lesions develop into necrotic ones. A varioliform-like scarring pattern can stay as a consequence. Often the disease is accompanied by pruritus, sometimes fever and arthralgias. In a very few number of cases, an ulcero-necrotic course of PLEVA (more in males) can be observed (UNMHD). This ulcero-necrotic course can become disastrous with high fever and involvement of mucous membranes in the oral, conjunctival and genital area with bacterial or viral superinfection. Splenomegaly, diarrhea, pneumonia, central-nervous symptoms, arthritis, sepsis and death can be observed.

PLC: Predominant are 2-10 mm round or oval, brownish-red papules with a small quite adherent squames at the center. During resolution of lesions, a leukoderma can persist.

• PLEVA: acute and subacute pityriasis lichenoides and varioliformis acuta (Mucha- Habermann disease).

  • subtype ulcero-necrotic (UNMHD type).

• PLC: pityriasis lichenoides chronica (Jadassohn – Juliusberg disease).

• Mixed Type.

Laboratory investigations for infections (upper respiratory and gastro-intestinal tract), differential blood count, biopsy and depending on the severity of course, other organs to be examined.

Depending on acuity.

• PLEVA: Focal hyper-and parakeratosis sometimes including neutrophilic granulocytes; spongiosis in the epidermo- papillary zone and exocytosis of lymphocytes into the basal layer resulting in an interface dermatitis and vacuolated keratinocytes; apoptosis of single keratinocytes, but dominant and increasing with necrotic course of the disease; strong perivascular lymphocytic (wedge shaped) infiltrate in the dermis and extravasation of erythrocytes including into the epidermis.

• PLC: Like in PLEVA, but less prominent.

Both types of pityriasis lichenoides last several weeks and months and can even be observed up to two years. In childhood up to 80% relapses can be observed.

Very rare transformation to malignant T-cell lymphoma.

In the chronic PL type usually none. However, PLEVA often results with small hypopigmented macules or varioliform scars. The FUMHD type can have deep scar lesions left. In the worst course of disease without appropriate intervention, death may occur (mostly due to cardiac complications).

The diagnosis in PL is clinical and can be substantiated by a biopsy. In PLEVA the diagnosis is also clinical, but due to differential diagnosis a biopsy should be performed.

• Psoriasis guttata

• Parapsoriasis

• secondary syphilis

• pityriasis rosea

• varicella

• vasculitis, Gianotti-Crosti-syndrome, drug reaction

No prevention.

Depending on course of disease, age and comorbidities.

Skin care, prevention of superinfection; erosive lesions may be treated topically with combined anti- microbial-glucocorticosteroid (class II-III) cream, pimecrolimus or tacrolimus. Phototherapy in PL can be considered. Severe courses with necrosis progress and fever and mucous membrane involvement should be treated immediately with methotrexate plus corticoid high dose pulse therapy. Other complicated courses should be treated in addition with erythromycin or azithromycin.