What Is Pityriasis Lichenoides?
Pityriasis lichenoides is an uncommon cutaneous condition of uncertain etiology or cause. The state is present in three different forms:
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Pityriasis lichenoides et varioliformis acuta (PLEVA)- Acute form.
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Pityriasis lichenoides chronica (PLC)- Chronic condition.
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Febrile ulceronecrotic Mucha-Habermann disease (FUMHD) - Rare, severe variant of PLEVA.
All three forms represent a spectrum of disease presentation. In some cases, these conditions can overlap, and features of both forms may be seen in the same person. It is a hypersensitivity reaction to a mild infection, but no specific bacteria or virus has been identified.
Who Gets Pityriasis Lichenoides?
It is estimated that pityriasis lichenoides affect around 1 in 2000 people yearly, with a slight male predominance. The disease is more often in late childhood to early adulthood, and it is rare in infants and older adults. However, the disease can be present in people of all ages and races.
What Causes Pityriasis Lichenoides?
The exact cause of pityriasis lichenoides is unknown. However, the experts believe it may be a hypersensitivity reaction to mild infection, such as:
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Viruses like Epstein-Barr, cytomegalovirus, human immunodeficiency virus, and hepatitis C.
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Parasites, such as Toxoplasma gondii.
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Bacteria, such as Staphylococcus and Streptococcus.
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An inflammatory reaction to a medication, including antihistamines, estrogen-progesterone therapy, measles vaccine, anti-TNF (tumor necrosis factor) agents, antidepressants, statins, vaccines, and radiocontrast dye.
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A low-grade lymphoproliferative disorder.
What Are the Clinical Features of Pityriasis Lichenoides?
PLEVA presents abruptly with a progressive rash. The clinical features of PLEVA include:
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10-50 bright red, flat to slightly raised, 5 to 10 mm (millimeter) oval spots.
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The lesions may evolve into vesicles, pustules, hemorrhagic crusts, and ulcers.
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They may appear singly or in groups and can merge into large areas of rash.
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The rashes are mainly seen on the trunk, thighs, upper arms, and flexural areas. In some cases, the face, palms, soles, and genitals are involved.
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There may be mild itching or burning, but no other symptoms are usually present in PLEVA.
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The rash may come and go, lasting for 1.5 to 18 months without intervention. Scarring and skin discoloration can occur afterward.
PLC is more common and has a milder presentation as compared to PLEVA. It often appears as:
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Subtle appearance of flat, red to brown oval spots.
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The lesions often affect the trunk, thighs, and upper arms.
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Fine mica-like scales develop at the edges and adhere to each lesion's center.
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People may experience a period of relapse and remission over the years. However, it does not cause scarring.
FUMHD is very rare, unlike PLEVA and PLC. Instead, it is considered a dermatologic emergency. It abruptly and dramatically presents as:
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The overall appearance of red to black ulcerated, necrotic plaques.
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Systemic symptoms like abdominal pain, high fever, diarrhea, joint pain, changes in mental status, and breathing difficulties accompany the lesions.
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People with FUMHD often require hospitalization. In addition, a 25 percent mortality rate is reported in people with FUMHD.
What Are the Possible Complications of Pityriasis Lichenoides?
PLEVA may result in scarring and skin discoloration. A rare severe form, FUMHD, has systemic symptoms, such as abdominal pain, high fever, diarrhea, lymphadenopathy, bacteremia, joint pain, changes in mental status, and breathing difficulties. So, there may be mucosal, gastrointestinal, and pulmonary involvement. In addition, mortality of up to 25 % is reported in FUMHD. Moreover, the psychological impact should be noticed, mainly when skin lesions occur on more easily visible areas, including the face and upper arms.
How Is Pityriasis Lichenoides Diagnosed?
The diagnosis of Pityriasis lichenoides is usually made on clinical features, but it is often confirmed with a skin biopsy. During a visit, the dermatologist orders a skin biopsy to look for the characteristic pattern of the skin inflammation. Blood tests may be done to rule out other causes of rash or identify potential infection triggers. PLEVA and PLC are not related to any abnormal blood tests. However, in FUMHD, increased white blood cell count and markers of inflammation may be seen. PLEVA can resemble other types of cutaneous lymphoma, so excluding other important differential diagnoses is essential. Other diagnostic tests, including screening for viral, bacterial, and toxoplasma infection, may be ordered, depending on the severity of the disease.
How Is Pityriasis Lichenoides Treated?
PLEVA and PLC usually resolve without treatment, which may take months or years. Treatment options include:
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A long course of antibiotics, like Erythromycin (in young children) or Tetracycline, is often given to people with PLEVA to decrease the duration of the disease. However, these antibiotics are mainly used for their anti-inflammatory properties rather than antibacterial effects.
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Topical corticosteroids may be prescribed to soothe itching.
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Antihistamines may help reduce the itch.
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Phototherapy, commonly a narrow-band UVB (ultraviolet B- rays) or PUVA (Psoralen P and ultraviolet A therapy), may also help treat PLEVA and PLC.
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Methotrexate and other immunosuppressive agents may be helpful for refractory or severe cases.
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Oral steroids are sometimes prescribed with antibiotics to speed the clearance of lesions.
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FUMHD is often treated in the hospital with medications including IV gamma globulin, Dapsone, Cyclosporine, and Methotrexate.
What Is the Outcome for People With Pityriasis Lichenoides?
PLEVA typically resolves within a few weeks. However, this can vary from person to person and may evolve into PLC or a scar. PLC typically persists for several months before resolving. FUMHD usually persists for several months before determining its own but occasionally recurs for several years.
Conclusion:
Pityriasis lichenoides is a rare skin condition of unknown cause. It can be present in three different forms- an acute form called Pityriasis lichenoides et varioliformis acuta (PLEVA), a chronic form called Pityriasis lichenoides chronica (PLC), and a rare type called Febrile ulceronecrotic Mucha-Habermann disease (FUMHD). The exact cause of pityriasis lichenoides is unknown. However, experts believe it may be a hypersensitivity reaction to mild infection. PLEVA usually heals within a few weeks. However, this variable may evolve into PLC, scar, or skin discoloration. While PLC typically persists for several months before resolving, FUMHD often persists for several months before resolving on its own but occasionally recurs for several years.
