It is a rarely reported condition, with an unknown prevalence and incidence. Most reported cases have occurred in pediatric patients, although adults can also be affected. Most of the reported cases are in females.
The condition is marked by recurrent episodes that are typically short-lived, often lasting a few minutes, but with some reports being up to several hours. The frequency of the episodes can vary from multiple times per day to less frequently, such as weekly or every few weeks.
The onset of the symptoms can occur during wakefulness and sleep. Some patients report tingling, pain, headache, flushing, burning and irritation, warmth, numbness, or fullness in the affected area shortly before bleeding.
There is a strong association with emotional or psychological stress. Some patients have preexisting psychiatric diagnoses, most commonly anxiety or depressive disorders.
It has rarely been associated with primary thrombocytopenic purpura, vicarious menstruation, otorrhea / otoerythrosis, isolated platelet deficiency, and platelet factor 3 (PF3) dysfunction. It has also been suggested that a genetic basis is possible due to reports occurring in siblings. A heterozygous CD36 mutation was found in 2 patients, although the clinical significance is unclear. Mutations in genes related to the extracellular matrix (ECM) and collagen chains have been noted in some cases as well.
Acute fear, intense mental stress, chronic stress, anxiety, psychological strain, and emotional distress are the most commonly identified triggers for the bleeding episodes. Other reported triggers include physical exertion, moving from cold to warm environments, prolonged exposure to heat, trauma (including preceding head injury or suspected surgical trauma), illness, or it can be idiopathic.
The exact etiology is unclear. There are 2 proposed mechanisms:
- During periods of physical or emotional stress, capillary vessels feeding sweat glands constrict. When the stressor subsides, the vessels dilate to the point of rupture, leading to blood passing through the sweat ducts.
- Defects in the dermis intermittently fill with blood due to increased vascular permeability and exude contents onto the surface of the skin. These defects subsequently collapse and disappear until blood flow is reestablished. In the literature, skin biopsies have not shown any cases of blood in sweat glands, which may support this latter etiologic theory.
