Pityriasis lichenoides represents a distinct subset of inflammatory skin disorders that includes

pityriasis lichenoides chronica Pityriasis lichenoides chronica is an uncommon, idiopathic, acquired dermatosis, characterized by evolving groups of erythematous, scaly papules that may persist for months. Freedberg, et al. (2003). ''Fitzpatrick's Dermatology in General Medici ...

, febrile ulceronecrotic Mucha-Habermann disease, and

pityriasis lichenoides et varioliformis acuta Pityriasis lichenoides et varioliformis acuta is a disease of the immune system. It is the more severe version of pityriasis lichenoides chronica. The disease is characterized by rashes and small lesions on the skin. The disease is more common in ...

(PLEVA). PLEVA typically manifests as an acute to subacute skin eruption of several tiny red papules that grow into polymorphic lesions. It may also leave behind varicella-like scars and hyper- or

hypopigmentation Hypopigmentation is characterized specifically as an area of Human skin, skin becoming lighter than the baseline skin color, but not completely devoid of skin pigment, pigment. This is not to be confused with depigmentation, which is characterize ...

sequelae.

Pityriasis lichenoides chronica Pityriasis lichenoides chronica is an uncommon, idiopathic, acquired dermatosis, characterized by evolving groups of erythematous, scaly papules that may persist for months. Freedberg, et al. (2003). ''Fitzpatrick's Dermatology in General Medici ...

(PLC) has very small reddish-brown flat maculopapules with a mica-like scale that appear more gradually; it also has long remission intervals between episodes of relapse. Febrile ulceronecrotic Mucha-Habermann disease (FUMHD) is best treated as a dermatological emergency because it is an acute, severe, widespread eruption of purpuric and ulceronecrotic plaques that can have a 25% fatality rate and accompanying systemic involvement.

Signs and symptoms

The characteristic feature of PLEVA is the rapid evolution of 2- to 3-mm-diameter erythematous macules into

papules A papule is a small, well-defined bump in the skin. It may have a rounded, pointed or flat top, and may have a dip. It can appear with a stalk, be thread-like or look warty. It can be soft or firm and its surface may be rough or smooth. Some ...

with a fine micaceous scale. The thicker the scale, the more frequently it breaks free at the edges while staying attached in the middle. The central punctum of the

papule A papule is a small, well-defined bump in the skin lesion, skin. It may have a rounded, pointed or flat top, and may have a umbilication, dip. It can appear with a Peduncle (anatomy), stalk, be thread-like or look warty. It can be soft or firm a ...

frequently develops into a vesiculopustular structure, experiences hemorrhagic

necrosis Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. The term "necrosis" came about in the mid-19th century and is commonly attributed to German pathologist Rudolf Virchow, who i ...

, ulcerates, and is covered in reddish-brown crusts. There may be postinflammatory hyper- and

as well as varioliform scars.

Pruritus An itch (also known as pruritus) is a sensation that causes a strong desire or reflex to scratch. Itches have resisted many attempts to be classified as any one type of sensory experience. Itches have many similarities to pain, and while both ...

and burning are among the symptoms. Although diffuse and widespread patterns can also occur, the trunk, extremities, and flexural areas are the most common sites for PLEVA to occur. Lesions can occur at any stage of development, making the eruption polymorphous. Subsequent crops of lesions can persist for weeks, months, or even years. The rapid progression of necrotic

to large coalescent ulcers with necrotic crusts, hemorrhagic bullae, and pustules distinguishes Febrile ulceronecrotic Mucha-Habermann disease from PLEVA. Both a secondary infection of the

ulcers An ulcer is a discontinuity or break in a bodily membrane that impedes normal function of the affected organ. According to Robbins's pathology, "ulcer is the breach of the continuity of skin, epithelium or mucous membrane caused by sloughing ...

and a large, painful

of the skin are possible. The mucosa of the mouth and genitalia may also be impacted. Atrophic scars and

are common after ulcer healing. PLC presents with a far slower clinical course than both febrile ulceronecrotic Mucha-Habermann disease and PLEVA. Similar to PLC, the lesion begins as an erythematous

that turns reddish-brown and is easily detached to reveal a shiny, pinkish-brown surface. The lesion also has a centrally adherent micaceous scale. In contrast to PLEVA and febrile ulceronecrotic Mucha-Habermann disease, the papule in question regresses and flattens on its own over a few weeks. Frequently, a hyper- or hypopigmented macule is left behind.

Diagnosis

The clinical examination of the skin is used to diagnose and distinguish between the various forms of pityriasis lichenoides. For pityriasis lichenoides, a

skin biopsy Skin biopsy is a biopsy technique in which a skin lesion is removed to be sent to a pathologist to render a microscopic diagnosis. It is usually done under local anesthetic in a physician's office, and results are often available in 4 to 10 day ...

followed by a histopathologic examination is a confirmatory procedure. Histologically, interface

dermatitis Dermatitis is a term used for different types of skin inflammation, typically characterized by itchiness, redness and a rash. In cases of short duration, there may be small blisters, while in long-term cases the skin may become thickened ...

with a noticeable lymphocytic infiltrate is the hallmark of pityriasis lichenoides.

References

External links

DermNet

Merck Manual
{{Papulosquamous disorders Lymphoid-related cutaneous conditions

Signs and symptoms

Diagnosis

References

Further reading

External links