This condition develops rapidly, typically within a few days to 1-2 weeks. It is characterized by a true polymorphism of the eruption, with the simultaneous appearance of papules, pustules, papulovesicles and hemorrhagic macules. Due to the waves of eruptions, there is an evolutionary polymorphism of elements: pustule or papule - erosion or ulcer - crust - secondary spot. Pathognomonic for the acute form of pityriasis lichenoides are papules with a hemorrhagic crust in the center, leaving small scars after resolution, and varioliform elements - pustular vesicles with a central dimple. Skin involvement is widespread and symmetrical.

Most often the eruptions are localized on the chest, back, abdomen and flexural surfaces of the proximal parts of the limbs. The skin of the palms, soles, hairy areas of the head, and face are unaffected.

In most cases, the general condition is unaffected, but sometimes fever, lymphadenopathy, general weakness, and pruritus may occur.

Duration is usually unpredictable and the disease can last from several weeks or months to even years. However, acute pityriasis lichenoides varioliformis usually has a shorter duration than the chronic form. In some cases, acute form may progress to chronic form.

Ulcerative-Necrotic Pityriasis Lichenoides et Varioliformis Acuta (Mucha-Habermann Disease): Characterized by an acute onset, development of febrile temperature (38-39°C), chills, generalized weakness and malaise, abdominal pain, headache, and lymphadenopathy. Single or, more commonly, multiple papules and/or plaques 5-15 mm in diameter appear on the skin. Rapid necrosis develops in their centers, followed by the formation of painful ulcers. Granulation of the ulcers leads to the formation of scars.

Primary Diagnostic Criteria:

• Fever
• Acute eruption of generalized ulcerative-necrotic papules and plaques.
• Rapid and progressive course without any tendency toward spontaneous resolution.
• Histopathological features as in pityriasis lichenoides et varioliformis acuta.

Additional Diagnostic Criteria:

• History of acute Pityriasis Lichenoides and Varioliformis in the patient's medical history.
• Involvement of oral mucosa.

This condition is characterized by a slow onset (weeks to months), a prolonged course (several years), and alternating periods of exacerbation and remission. Subjective sensations are usually absent, although some patients may experience mild pruritus.

Primary morphologic element is a flat, round papule measuring 4-10 mm. It is initially pink or red in color and then turns yellowish-brown. The infiltrate at the base of the papule is minimal and the eruptions do not coalesce or cluster. Eruptions are typically located on the chest, abdomen, back, proximal parts of the limbs, and are particularly characteristic on the inner surface of the shoulders. Eruptions are not observed on the face, scalp, palms and soles.

Papules are firm with a smooth surface. When scraped, they show scaling (symptom of hidden scaling) followed by pinpoint bleeding (symptom of purpura). As papules develop, they take on a brownish color. Approximately 1-2 weeks later, a tightly adherent, centrally located, and well-demarcated serous brown scale appears on their surface, which, when carefully removed, completely detaches (scale sign). After complete resolution of the papule, a matte white scale remains in its place as a thin film attached to the underlying skin. Eruptions may occur at different stages during the course of the disease.

After several weeks, papules spontaneously resolve, leaving behind secondary hyperpigmented or hypopigmented spots. There is usually a tendency for improvement during summer months, probably due to natural ultraviolet radiation.