Macules: Flat, nonpalpable, circumscribed areas of discoloration ≤0.5 cm in diameter. Typical macules
are the familiar freckles.
Patches: Flat, nonpalpable areas of skin discoloration >0.5 cm in diameter (i.e., a large macule). A typical
patch is the one of vitiligo.
Papules: Raised and palpable lesions ≤0.5 cm in diameter. They may or may not have a different color
from the surrounding skin. A typical papule is a raised nevus.
Plaques: Raised and palpable lesions >0.5 cm in diameter (i.e., a large papule). Usually confined to the
superficial dermis, they may result from the confluence of papules. A typical plaque is that of psoriasis.
Nodules: Raised, palpable, and elevated lesions >0.5 cm in diameter, which, unlike plaques, go deeper
into the dermis. Since they are below the surface of the skin, the overlying cutis is usually mobile.
Typical nodules are those of erythema nodosum.
Tumors: Nodules that are either >2 cm in diameter or poorly demarcated. Usually neoplastic.
Wheals (hives): Raised, circumscribed, edematous, and typically pruritic plaques that are pink or pale but
typically transient. Classic wheals are the lesions of urticaria, or of a mosquito bite.
Vesicles (blisters): Fluid-filled, circumscribed, and raised lesions that contain clear serous fluid and are ≤0.5 cm in diameter. Typical vesicles are those of herpes simplex.
Bullae: Vesicles >0.5 cm in diameter. Commonly seen in patients with second-degree burns. Presence
of a bulla is so important that it usually trumps all other concomitant primary lesions.
Cysts: Raised and encapsulated lesions that contain fluid or semi-solid material. Typical are the cysts of
acne.
Pustules: Pus-filled papules. Typically seen in patients with impetigo or acne.
Purpura: Skin extravasation of red cells, which, based on size, may present as petechiae or
ecchymoses. Palpable purpura is never normal and argues for an antigen-antibody complex (vasculitis).
Often localized to the lower extremities, the lesions of Henoch-Schönlein are typical examples of a
palpable purpura. Internal organs (kidneys, GI tract) are often involved too.
Petechiae: Reddish-to-purple discolorations, caused by a microscopic hemorrhage. These are <0.5 cm in
diameter and usually in clusters. With the exception of color, they resemble papules or macules
(depending on whether they are palpable or not). Typical petechiae are those of typhus. The lesions of
thrombocytopenic thrombotic purpura (TTP) are typical petechiae too.
Ecchymoses (bruises): Reddish-to-purple discolorations larger than petechiae. Except for color,
they resemble plaques and patches (depending on whether they are palpable or not). Typically located
below an intact epithelial surface.
Spider angiomas: These are arterial teleangiectasias, i.e., vascular arterial lesions that resemble the legs of
a spider. They fill from the center and blanch whenever this is compressed.
Venous spiders: These are venousteleangiectasias, i.e., vascular venous lesions that also resemble the
legs of a spider. Hence, they fill from the periphery, not the center. They empty with pressure.
are the familiar freckles.
Patches: Flat, nonpalpable areas of skin discoloration >0.5 cm in diameter (i.e., a large macule). A typical
patch is the one of vitiligo.
Papules: Raised and palpable lesions ≤0.5 cm in diameter. They may or may not have a different color
from the surrounding skin. A typical papule is a raised nevus.
Plaques: Raised and palpable lesions >0.5 cm in diameter (i.e., a large papule). Usually confined to the
superficial dermis, they may result from the confluence of papules. A typical plaque is that of psoriasis.
Nodules: Raised, palpable, and elevated lesions >0.5 cm in diameter, which, unlike plaques, go deeper
into the dermis. Since they are below the surface of the skin, the overlying cutis is usually mobile.
Typical nodules are those of erythema nodosum.
Tumors: Nodules that are either >2 cm in diameter or poorly demarcated. Usually neoplastic.
Wheals (hives): Raised, circumscribed, edematous, and typically pruritic plaques that are pink or pale but
typically transient. Classic wheals are the lesions of urticaria, or of a mosquito bite.
Vesicles (blisters): Fluid-filled, circumscribed, and raised lesions that contain clear serous fluid and are ≤0.5 cm in diameter. Typical vesicles are those of herpes simplex.
Bullae: Vesicles >0.5 cm in diameter. Commonly seen in patients with second-degree burns. Presence
of a bulla is so important that it usually trumps all other concomitant primary lesions.
Cysts: Raised and encapsulated lesions that contain fluid or semi-solid material. Typical are the cysts of
acne.
Pustules: Pus-filled papules. Typically seen in patients with impetigo or acne.
Purpura: Skin extravasation of red cells, which, based on size, may present as petechiae or
ecchymoses. Palpable purpura is never normal and argues for an antigen-antibody complex (vasculitis).
Often localized to the lower extremities, the lesions of Henoch-Schönlein are typical examples of a
palpable purpura. Internal organs (kidneys, GI tract) are often involved too.
Petechiae: Reddish-to-purple discolorations, caused by a microscopic hemorrhage. These are <0.5 cm in
diameter and usually in clusters. With the exception of color, they resemble papules or macules
(depending on whether they are palpable or not). Typical petechiae are those of typhus. The lesions of
thrombocytopenic thrombotic purpura (TTP) are typical petechiae too.
Ecchymoses (bruises): Reddish-to-purple discolorations larger than petechiae. Except for color,
they resemble plaques and patches (depending on whether they are palpable or not). Typically located
below an intact epithelial surface.
Spider angiomas: These are arterial teleangiectasias, i.e., vascular arterial lesions that resemble the legs of
a spider. They fill from the center and blanch whenever this is compressed.
Venous spiders: These are venousteleangiectasias, i.e., vascular venous lesions that also resemble the
legs of a spider. Hence, they fill from the periphery, not the center. They empty with pressure.
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