Pityriasis lichenoides is a rare form of dermatitis that can present in acute and chronic forms. The cause is still unknown and is most commonly observed in children and adolescents. The clinical presentation includes scaling papules with necrosis and crusting. The diagnosis is made by skin biopsy. Treatment is usually not necessary but symptomatic treatment and occasionally, antibiotic treatment and phototherapy is used.
The clinical presentation of pityriasis lichenoides involves the appearance of typical skin lesions over the course of weeks or even months and may be accompanied with symptoms such as fever, malaise and headache (in which case Mucha-Habermann disease is suspected). PLEVA is characterized by the appearance of red edematous papules, or in some cases vesicles. These lesions may be pruritic and painful to touch, eventually becoming necrotic and undergo crusting, often with hemorrhage . The lesions randomly appear and develop at any site on the skin, including the trunk, extremities, palms, soles, face and the scalp.
Pityriasis lichenoides chronica (PLC) has some distinguishing characteristics from PLEVA. Lesions that are seen in patients with chronic form are reddish-brown papules that have mica-like scales. Other distinct features include absence of pruritis, and the fact that lesions are painless to touch. For lesions in both acute and chronic forms, hypo and hyperpigmentation is often observed after resolutions of skin lesions. Scarring may occur as well.
It is important to know that patients may exhibit both acute and chronic forms of the disease simultaneously, which creates a significant challenge in establishing a diagnosis.
The diagnostic workup in patients with pityriasis lichenoides comprises various laboratory tests and skin biopsy.
Because infectious etiologies have been strongly implicated in the pathogenesis of this disease, several pathogens should be tested for. EBV IgM/IgG titers, Hepatitis B surface antigen (HBs), anti-hepatitis C IgM antibodies (anti-HCV), HIV ELISA test, Toxoplasma gondii IgG and herpes simples virus IgM/IgG titers should be performed in all patients to identify possible infectious pathogens.
However, the gold standard in the diagnosis of pityriasis lichenoides is skin biopsy and subsequent histopathologic examination . Various changes are observed, both epidermal and dermal. Epidermal abnormalities include spongiosis, vesiculation, ulceration, and erythrocytic exocytosis, while dermal edema and infiltration of chronic inflammatory cells, as well as hemorrhage, congestion, and swelling of the endothelial cells are changes observed in the dermis .
So far, treatment regimens have not been standardized for pityriasis lichenoides, but options include antibiotic therapy and ultraviolet radiation . The exact mechanisms of therapeutic efficacy is not entirely known for either regimen, but they are presumably effective because of their anti-infective and immunomodulating properties, respectively. Treatment may not be required in all patients, as lesions may resolve on their own.
Oral administration of erythromycin, a macrolide bacteriostatic antibiotic, has been shown to be effective in improving skin lesions in many patients, while alternatives include tetracycline, cephalexin, and azithromycin. Ultraviolet radiation comprises both UV B and UVA phototherapy, with various regimens showing significant rates of improvement.
However, despite these suggested regimens, recurrence of lesions may occur in a significant number of patients. Systemic administration of imunosuppressive agents, such as methotrexate, cyclosporine, or dapsone have been recommended for use in severe and recurrent cases. Since tumor necrosis factor-alpha (TNF-α) has shown increased values in patients with more severe forms of the disease, anti-TNF agents are being considered potentially for therapy .
The overall prognosis for patients with this skin disease is good, as the skin lesions resolve almost completely within a few months in the majority of cases without therapy . However, recurrences have been documented, and severe ulcero-necrotic forms of skin lesions can develop in patients. Fortunately, these cases are very rare . Because of its potential progression into cutaneous lymphoma, long-term monitoring should be conducted in all patients, especially in those that experience recurrent lesions.
The cause of pityriasis lichenoides is still not known and various agents have been implicated. Theories that have been mentioned include:
It is known that pityriasis lichenoides is a rare disease and is not commonly encountered in clinical practice. Its incidence and prevalence rates are not established. This skin disease is most commonly identified in children, but this disorder may be diagnosed in adolescents and young adults as well . For unknown reasons, a male predominance has been observed, while ethnic predilection has not been established.
The pathognesis of pityriasis lichenoides remains unclear at the moment. One of the theories is that both acute and chronic forms of this skin disease result following an inflammatory reaction triggered by an external stimulus, such as an infection or some medication, while T cell dyscrasia, which implies abnormal lymphocytic proliferation, has also been implicated in the pathogenesis. The fact that parts of the complement system, including C3, C4, as well as IgM have been found in histopathological specimens, as well as phenotypic abnormalities and T-cell receptor (TCR) changes, further strengthen the hypothesis that pityriasis lichenoides stems from alterations in the immune system .
At this moment, prevention strategies against this clinical entity are not known, as the underlying cause is not yet established.
Pityriasis lichenoides is a rare skin disease that most commonly develops in children and adolescents and the exact cause of this dermatitis is still unknown. Several theories have been proposed, and include infectious, immune-mediated and iatrogenic causes . It is also associated with cutaneous T-cell lymphoma, as studies have shown progression of lesions encountered in these patients progress to this form of malignancy. This disorder is more commonly encountered amongst males. Pityriasis lichenoides has two clinical forms - acute, also known as pityriasis lichenoides et varioliformis acuta (PLEVA); and chronic, known as pityriasis lichenoides chronica (PLC). Additionally, Mucha-Habermann disease (MHD) is an acute form of PLEVA and febrile ulceronecrotic Mucha-Habermann disease (FUMHD), considered as a dermatologic emergency, is the most severe variant of PLEVA. It is important to note that patients may exhibit signs of both acute and chronic types simultaneously . Red edematous papules (known as lichenoides) are lesions typically present in acute forms of the disease and are often randomly distributed on the skin. Necrotic vesicles with hemorrhagic crusting (known as varioliformis) develop from these papules after some time. The vesicles initially appear on the trunk and the extremities, but may appear all over the body too. Pityriasis lichenoides chronica is characterized by red or brown scaling papules. Either hypo or hyperpigmentation may be observed at the site of the lesion after their resolution. Apart from the skin lesions, patients may sometimes develop constitutional symptoms, such as malaise and headache. If fever is present, FUMHD should be suspected. The initial diagnosis is made clinically, during physical examination, while a definite diagnosis is made with a skin biopsy. Spongiosis, ulceration, dermal edema, chronic inflammation and hemorrhage are some of the findings encountered during microscopic examination. The prognosis is usually good and the majority of patients do not require treatment, as lesions spontaneously resolve within weeks or months. Relapses may occur, in which case some form of therapy may be indicated. Oral antibiotics, such as erythromycin, tetracycline, and ultraviolet therapy, either UVB or photochemotherapy (PUVA) have shown good results in various studies, but treatment guidelines have yet to be standardized.
Pityrasis lichenoides is a rare skin disease that is most frequently encountered in children and young adults. The exact cause of this type of skin rash is not known, but several theories that include infections, alterations of the immune system, as well as certain medications, have been proposed. There are two distinct forms - acute, known as pityriasis lichenoides et varioliformis acuta (PLEVA) and chronic, known as pityriasis lichenoides chronica (PLC). Each form has some distinguishing characteristics, but in general, patients with this disease present with a rash that develops over the course of weeks or months. The rash initially consists of small red papules that are slightly elevated over the skin and eventually turn into crusts. The rash can appear on the trunk and the extremities, but it can appear on the entire body, and in the acute form, the rash is both itchy and painful to touch. At this point, the lesions may spontaneously resolve, or patients may progress to chronic forms, in which the rash consists of reddish to brown papules that crust and show small bleeding points, often with hypo or hyperpigmentation of the skin. In the chronic form, the rash is not itchy and is painless to touch. Patients may exhibit both acute and chronic form of the disease at the same time, which presents as a significant challenge for the physician. The initial diagnosis of pityriasis lichenoides is made during physical examination, while a definite confirmation is obtained by performing a skin biopsy, which will reveal various skin changes which are hallmarks of this condition. Treatment may not be necessary, as the rash commonly resolves on its own, but because the exact cause of pityriasis lichenoides is not known, treatment guidelines are still not determined. Oral antibiotics, such as erythromycin and tetracycline, as well as ultraviolet radiation have been proposed as therapeutic strategies, and have shown good results in patients. Immunosuppressive agents, such as methotrexate and cyclosporine have been used as well, but their effects remain to be seen in larger studies. Additional therapy may include topical corticosteroids and antihistamines to cope with itching. Patients usually have a good prognosis, as the lesions resolve either with or without adjunctive therapy. But it has been established that rare cases of pityriasis lichenoides transform into lymphoma of the skin, which is why a prompt diagnosis and close monitoring of these patients is necessary in maintaining good outcomes.