Which of the following statements best describes the involvement of the immune system in psoriasis etiology?

Explanation: Auspitz sign is a characteristic finding in psoriasis where pinpoint bleeding occurs when scales on the skin are removed. It is caused by the rapid growth and shedding of skin cells, which leads to the formation of delicate blood vessels that bleed easily.

Incorrect choices: a. Auspitz sign is not related to increased bleeding tendency in the patient; it is specific to psoriasis and its characteristic skin changes.

b. Presence of skin pustules and blisters is not associated with Auspitz sign and may indicate other skin conditions.

c. Formation of deep fissures in the skin is not directly related to Auspitz sign, which focuses on the bleeding after scale removal.

Explanation: The presence of at least 3 typical psoriasis plaques on the body is one of the essential diagnostic criteria for confirming psoriasis. These plaques are characterized by well-defined, erythematous (red), raised lesions with silvery-white scales.

Incorrect choices: a. Positive skin biopsy showing eosinophils infiltration: While a skin biopsy may be performed to support the diagnosis of psoriasis, the presence of eosinophils is not specific to psoriasis and can be found in various skin conditions.

b. Family history of autoimmune diseases: A family history of autoimmune diseases may increase the risk of developing psoriasis, but it is not a definitive diagnostic criterion for the condition.

d. Elevated erythrocyte sedimentation rate (ESR) on blood test: An elevated ESR can indicate inflammation in the body, but it is not specific to psoriasis and may be present in other inflammatory conditions as well.