Tutorial A: The Primary Lesions

Primary lesions are physical changes in the skin considered to be caused directly by the disease process. Types of primary lesions are rarely specific to a single disease entity.

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Macule

A macule is a change in the color of the skin. It is flat, if you were to close your eyes and run your fingers over the surface of a purely macular lesion, you could not detect it. A macule greater than 1 cm. may be referred to as a patch.

This 18 month old with neurofibromatosis has characteristic cafe-au-lait macules.

This 3-year-old girl with tuberous sclerosis has hypopigmented macules and patches.

This nearly 8-year-old boy has the red macular rash associated with the viral disease erythema infectiosum, also known as fifth disease.

Papule

A papule is a solid raised lesion that has distinct borders and is less than 1 cm in diameter. Papules may have a variety of shapes in profile (domed, flat-topped, umbilicated) and may be associated with secondary features such as crusts or scales.

These are the papules of molluscum contagiosum in a 3-year-old girl.

This nearly 5-year-old boy has hundreds of papules with an id reaction. An id reaction is a generalized hypersensitivity reaction on the skin to a local inflammatory lesion of the skin (e.g., a fungal infection).

This plaque of tinea corporis (cutaneous fungal infection) is a papulosquamous lesion.
*Another commonly used descriptive term is “papulosquamous.” Papulosquamous lesions are raised and scaly.*

Nodule

A nodule is a raised solid lesion more than 1 cm. and may be in the epidermis, dermis, or subcutaneous tissue.

The nodule in the axilla of this 6-year-old boy is a lymph node associated with cat-scratch disease.

Tumor

A tumor is a solid mass of the skin or subcutaneous tissue; it is larger than a nodule. (Please bear in mind this definition does not at all mean that the lesion is a neoplasm.)

These xanthomas are tumors that appeared in a 7-year-old girl with hepatic dysfunction secondary to Langerhans cell histiocytosis.

Plaque

A plaque is a solid, raised, flat-topped lesion greater than 1 cm. in diameter. It is analogous to the geological formation, the plateau.

These are the extensive plaques of psoriasis covered with a characteristic silvery scale in an 18-year-old young man.

Vesicle

Vesicles are raised lesions less than 1 cm. in diameter that are filled with clear fluid.

Bullae

Bullae are circumscribed fluid-filled lesions that are greater than 1 cm. in diameter.

This 4-year-old boy has bullae on the pinna of his ear from a contact dermatitis.

Pustule

Pustules are circumscribed elevated lesions that contain pus. They are most commonly infected (as in folliculitis) but may be sterile (as in pustular psoriasis).

Wheal

A wheal is an area of edema in the upper epidermis.

This 2-year-old girl has a wheal from an insect bite.

Burrow

Burrows are linear lesions produced by infestation of the skin and formation of tunnels (e.g., with infestation by the scabitic mite or by cutaneous larva migrans).

Telangiectasia

Telangiectasia are the permanent dilatation of superficial blood vessels in the skin and may occur as isolated phenomena or as part of a generalized disorder, such as ataxia telangiectasia.