Everybody has occasional bruising after minor trauma or even without a noticed trauma at all. There is large inter-individual variation in sensitivity. Solitary bruises, even without a noticed trauma, are usually harmless and do not necessarily require further laboratory investigations.
Keep in mind that purpura can be caused by meningococcaemia or other severe infection (often febrile patient in poor general condition) and in such a case arrange for immediate further treatment.
Other causes to be investigated and treated include medications, autoimmune diseases and increased bleeding tendency.
Terminology
Purpura is a group of disorders characterized by intradermal or submucosal haemorrhages that are purplish or brownish red in colour, and they may be raised (palpable purpura).
Petechiae are well-defined small (1-3 mm), intradermal or submucous spots caused by haemorrhage. They are not elevated from the skin. They do not disappear when pressed, for example, with a glass. Note the difference to haemangiomas and telangiectases.
An ecchymosis is a haemorrhagic spot, like a petechia, but larger in size.
Need for further investigations
The following are typical of "non-pathological" bruising and do not require additional investigation:
a bruise is formed at the site of trauma
a single bruise (< 3 cm) anywhere on the body of a patient with no other symptoms; unnoticed bruises are common, especially on the limbs
bruises on the arms and on the back of the hands of an elderly patient, caused by excessive movement of the skin resulting in capillary breaks (senile purpura).
Petechiae do not require additional investigation if
the patient has cardiac or vein insufficiency and petechiae are located in the legs and are aggravated by oedema (walk, hot weather, sauna).
Petechiae and bruises always require additional investigation if
the patient also has other symptoms of unknown origin, such as fever, tiredness etc.
they are formed spontaneously in various sites of the body, even if the patient has no other symptoms.
In these cases it should be clarified whether or not the patient has a haemorrhagic disorder or purpura.
Causes of purpura
Purpura is common in diseases affecting blood vessels and platelets (thrombocytopenia or -pathy), but is uncommon in coagulopathies.
Autoimmune diseases
Allergic purpuras
Henoch-Schönlein purpura is frequently associated with arthralgia and gastrointestinal symptoms Henoch-Schönlein Purpura.
Infection which is commonly associated with purpura; remember the possibility of meningococcaemia if the patient is in poor condition and feverish.
Physical abuse
For orientation, some laboratory investigations are helpful
Complete blood count
Urinalysis (microscopic haematuria?)
C-reactive protein (bacterial infection?).
In adults, start with investigating the use of drugs that impair platelet function, such as ASA or other non-steroidal anti-inflammatory analgesics, clopidogrel or other ADP receptor blockers, SSRI-type antidepressants and omega-3 fatty acids. Also take the use of anticoagulants into account.
If an otherwise symptomless patient has used NSAIDs, easy bruising is probably a result of these drugs. Check complete blood count. The medication should be stopped or replaced with paracetamol or a cyclooxygenase-2 inhibitor (but consider the cardiovascular adverse effects of the latter) and the clinical situation checked after one month. If purpura is still present, further investigations are indicated. If purpura is massive or sudden, it is advisable to initiate the above-mentioned laboratory investigations, even if the patient is using NSAIDs.
If the patient is using oral anticoagulants and has bruising but is otherwise symptomless, then INR measurement helps in orientation. If the value is within the therapeutic range, the possible role of oral anticoagulants in bruising is explained to the patient. The patient is counselled to contact the physician if the bruising tendency increases or if general symptoms appear. Markedly increased bruising or petechiae in a patient on anticoagulant therapy requires immediate clinical assessment and laboratory tests (basic blood count with platelets, creatinine).
The medication is checked in order to reveal drugs possibly causing thrombocytopenia or platelet dysfunction. Drugs used during the last month before purpura are of the most interest. The antihaemostatic effect of NSAIDs lasts about one week.
Infections as a cause of purpura must be checked (remember the possibility of a septic infection if the patient is in poor condition or feverish).
If there are no simple explanations for purpura, such as drugs or an infection, the next question to be answered is: does the patient have an increased tendency to bleed (most likely one affecting platelet function, usually thrombocytopenia), or does purpura have a vascular aetiology (allergic, skin disease)?
Platelet count is part of the primary laboratory investigations if the platelet count is below 100 × 109 /l, the cause of thrombocytopenia should be clarified (see thrombocytopenia, Thrombocytopenia and ITP, Thrombocytopenia).
If thrombocytopenia is excluded (platelet count > 100 × 109 /l) platelet function testing with a PFA device may provide clues whether the patient has a primary haemostatic abnormality. It may also reveal the possible effect of aspirin. If Henoch-Schönlein purpura is unlikely, the accurate diagnosis of vascular diseases often requires skin biopsy and immunohistochemistry (skin biopsy, see Skin Biopsy: Indications and Technique).
If platelet count is clearly decreased or platelet function is impaired, the patient should be referred to specialist care (unless the condition can be explained by e.g. medication).