Chapter 77: The Vascular Purpuras

DEFINITIONS

• Purpura is the extravasation of red cells from vasculature into the skin and/or subcutaneous tissues.

• Petechiae are red-purple lesions less than 2 mm in diameter.

• Purpura describes red-purple lesions 2 mm to 1 cm.

• Ecchymoses are red-purple lesions greater than 1 cm.

• Erythema is reddened skin due to increased capillary flow.

• Telangiectasia is dilated superficial capillaries.

• Erythema and telangiectasia blanch with pressure, and petechiae and purpura do not. This can be easily demonstrable with a glass microscope slide.

PATHOPHYSIOLOGY

• Hemostatic mechanisms may be unable to protect against minor vascular trauma.

• Vessels and surrounding tissues may be weakened structurally.

• Transmural pressure gradient may be too great.

• Palpability may result from:

  — Extravascular fibrin deposition

  — Cellular infiltration due to inflammation or malignancy

NONPALPABLE PURPURA

Increased Transmural Pressure Gradient

• Increased intrathoracic pressure caused by coughing, vomiting, weight lifting, etc. may cause petechiae of the face, neck, and upper thorax.

• Venous valvular incompetence or tight clothing may cause petechiae on the lower extremities.

Decreased Mechanical Integrity of the Microvasculature or Supporting Tissues

• Actinic (senile) purpura is red to purple irregular patches on the extensor surfaces of the forearm and hands.

• Glucocorticoid excess causes bright red purpuric lesions in thin, fragile skin on flexor and extensor surfaces of both arms and legs.

• Vitamin C deficiency (scurvy) results in a susceptibility of lysyl and prolyl hydroxylases to inactivation, which are two key enzymes in collagen biosynthesis in the skin. This leads to follicular hyperkeratosis, petechiae, and perifollicular purpura with entrapped corkscrew hairs. Large ecchymoses and hemorrhagic gingivitis, stomatitis, and conjunctivitis may occur.

• Ehlers-Danlos syndrome is characterized by easy bruising in types IV and V, but this may occur with other types as well.

• Pseudoxanthoma elasticum may be associated with recurrent mucosal hemorrhages.

• In amyloidosis, infiltration of blood vessel walls may lead to increased vascular fragility and petechiae or purpura.

• The female easy-bruising syndrome (purpura simplex) is purpura or ecchymoses occurring predominantly in women, frequently on the thighs. This may be related to hormonal changes and can be aggravated by nonsteroidal anti-inflammatory drug (NSAID) ingestion.

TRAUMA

• Physical trauma can cause cutaneous bleeding. The history, shape, and location of the lesions may suggest the etiology.

• Factitial purpura usually presents as medium to large ecchymoses on the lower extremities of patients who appear unconcerned about the lesions.

SUNBURN

• Acute sunburn may be sufficiently severe to have a petechial component.

INFECTIONS

• Purpura may occur with bacterial, fungal, viral, or rickettsial infections, or with parasitic infestations, including protozoan, often as a consequence of a complex, multifactorial process. Special forms include:

  — Bacterial sepsis due to various organisms can cause petechiae or purpura, macules or papules, hemorrhagic bullae, erosions, ...