Benign mechanical petechiae

mechanical petechiae · cough petechiae · SVC distribution petechiae · traumatic petechiae · non-blanching rash - benign causes

The commonest benign cause of a non-blanching rash in a child - but it is a diagnosis of exclusion made on a well child, never on the rash alone.

DISCHARGEBand B

Red flags

Any petechiae below the nipple line, or a rash that does not fit an SVC distribution
Lesions larger than 2 mm in diameter - NICE NG143 lists purpura among the features pointing to meningococcal disease
Fever, an ill-looking child, capillary refill of 3 seconds or more, or neck stiffness - the other NG143 features
A rash that is spreading or increasing in number during observation
Any child you are not sure about - treat as meningococcal and give antibiotics

Recognise

On light skin

Pinpoint red-purple petechiae that do not blanch, confined above the nipple line in a well child with a history of retching, coughing or prolonged crying.

On brown and black skin

Petechiae are hard to see in brown and black skin, which cuts both ways: a benign mechanical rash may be missed entirely, and - far more dangerously - a meningococcal rash may be under-appreciated and wrongly filed here. NICE NG240 says directly that rashes can be hard to detect on brown, black or tanned skin and instructs you to look for petechiae in the conjunctiva. Examine the conjunctivae, palms, soles and oral mucosa, undress the child fully including the nappy area, and use good light. Never let a hard-to-see rash become a reassuring one.

In any skin tone

The child is well - this is the load-bearing feature, not the rash
A clear mechanical history: forceful coughing, vomiting, retching or prolonged crying immediately beforehand
Strictly confined to the SVC distribution, above the nipple line, with nothing below it. Know where this threshold comes from: a single prospective cohort of 190 febrile children, in which no child with invasive bacterial disease had petechiae only above the nipple line. It is a supportive feature in a well child, not a validated rule, and no UK guideline endorses it
Lesions are pinpoint petechiae, not purpura - NICE flags lesions larger than 2 mm as concerning
Not spreading - re-examine after a period of observation and confirm the count has not risen

Distribution

Confined to the distribution of the superior vena cava - head, neck and upper chest, above the nipple line - after forceful coughing, vomiting or crying. Also seen locally under a tourniquet, a tight strap or a bite.

Photographs

Benign mechanical petechiae on the face after forceful vomiting. Crops of tiny non-blanching red-purple spots over the forehead, eyelids, cheeks and nose. **The distribution is the diagnosis**: these are confined to the territory drained by the superior vena cava - head, neck and upper chest above the nipple line - because the pressure spike of coughing, vomiting or hard crying is transmitted up the valveless head and neck veins. Petechiae **below** that line do not fit this explanation and must be taken seriously. This remains a diagnosis of exclusion made on a well child with a normal examination, never on the rash alone: if the child is unwell, has petechiae elsewhere, or you are not certain, investigate for meningococcal disease and for a low platelet count. On brown and black skin these are easier to find on the conjunctivae, the palate and the eyelids than on the cheeks. The publisher masked the eyes.
Fitzpatrick IV (Fitzpatrick type estimated from the photograph, not stated by the source) · Kaliyadan F, Kuruvilla JP, Indian Dermatology Online Journal · Kaliyadan F, Kuruvilla JP. Post-vomiting purpura. Indian Dermatol Online J 2016;7(5):456-457, Figure 1 · CC BY-NC-SA 3.0

Provenance for every photograph in this library: image licences. How much of the corpus still has no darker-skin photograph: skin tone coverage.

Mimics

Meningococcal septicaemia and purpura fulminans — The reason this entry exists. Meningococcal purpura is not confined to the SVC distribution, the child is unwell, and lesions are often larger than 2 mm
IgA vasculitis (Henoch-Schonlein purpura) — IgA vasculitis purpura is palpable and sits on the buttocks and extensor legs, not the face and upper chest

What to do in the ED

Treat every non-blanching rash as meningococcal until the assessment says otherwise - the benign diagnosis is reached by exclusion, not by pattern recognition
Undress the child completely and examine the whole skin, including the nappy area and the conjunctivae
Assess against the meningococcal red flags in NICE NG240 1.1.9, which covers babies, children, young people and adults: a haemorrhagic non-blanching rash with lesions larger than 2 mm, a rapidly progressive or spreading non-blanching petechial or purpuric rash, or any signs of bacterial meningitis combined with a non-blanching rash. NG143's version of the same list (ill appearance, lesions over 2 mm, capillary refill of 3 seconds or more, neck stiffness) applies to under 5s only, and this rash is common in school-age children
If the child is febrile or unwell at all, give antibiotics and investigate - do not attribute the rash to coughing
If the child is afebrile, well, and the rash fits the SVC distribution exactly, observe and re-examine rather than discharging immediately
Document the distribution, the largest lesion size, and the count, so that progression can be measured by whoever sees them next

Disposition

DISCHARGE

A well, afebrile child with petechiae confined above the nipple line and a clear mechanical history may be discharged after a period of observation and re-examination. Anything else is a paediatric assessment.

Safety-netting

Return immediately if the child develops a fever, becomes drowsy, floppy or difficult to wake, if the spots spread below the nipple line or increase in number, if any spot becomes larger than a pinpoint, if the hands and feet become cold or mottled, or if you are simply worried they are getting worse. Show parents how to do the glass test but tell them plainly that a rash which blanches, or no rash at all, does not mean it is safe to stay at home.

Sources

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