Primary morphological elements

Primary morphological elements (from Greek morphe — form and logos — study) are primary skin lesions, representing clinical manifestations of skin diseases that occur on unaltered (healthy) skin. These lesions are what suggest the onset of any dermatosis.

Correct identification of the type of primary lesion (spot, nodule, vesicle, etc.) is key to making an accurate dermatological diagnosis.

Classification

All primary lesions are divided into two main groups:

• Cavitated, which have an internal cavity filled with contents (serous, hemorrhagic, or purulent). These include vesicle, blister, pustule.
• Non-cavitated (infiltrative), which do not have a cavity and represent a change in color or cell accumulation in the layers of the skin. These include spot, papule, nodule, wheal, and tubercle.

Clinical significance

The evolution (development) of primary lesions leads to the emergence of secondary elements (crusts, erosions, ulcers, and scars). A dermatologist always strives to identify the primary lesion, as secondary changes are often less specific and can obscure the true cause of the disease.