Gianotti-Crosti syndrome

GCS · papular acrodermatitis of childhood · infantile papular acrodermatitis

A symmetrical papular eruption on the cheeks, buttocks and extensor limbs of a well child, sparing the trunk - a post-viral rash that needs recognition, not treatment.

GPBand B

Red flags

Jaundice, dark urine or hepatomegaly - the syndrome's historical association is with hepatitis B, and that association is the reason the rash is worth naming rather than shrugging at
A child who is systemically unwell: Gianotti-Crosti itself does not make a child ill, so look for another diagnosis

Recognise

On light skin

Monomorphous, flat-topped, pink to pink-brown papules or papulovesicles 1-10 mm across. They are notably uniform - a field of lesions that all look the same age and the same size, rather than the mixed crops of chickenpox.

On brown and black skin

The pink component of the described pink-brown papule is simply not visible, so the eruption reads as skin-coloured, brown or violaceous flat-topped papules and is easy to dismiss as unremarkable. Diagnose this one by touch and by distribution rather than by colour - run a hand over the cheeks, buttocks and extensor limbs, because monomorphous papules are palpable across the whole Fitzpatrick range even when they are barely visible. Expect prominent and long-lasting post-inflammatory hyperpigmentation as it settles, which is a feature of pigment lability in darker skin rather than of this disease, and warn the family so the marks are not read as the rash failing to clear. No skin-of-colour series specific to Gianotti-Crosti syndrome was found - that statement is drawn from general sources on paediatric skin of colour, not from a study of this condition.

In any skin tone

Monomorphous flat-topped papules or papulovesicles, 1-10 mm, all of one type
Symmetrical, on at least three of: cheeks, buttocks, extensor forearms, extensor legs
Extensive truncal lesions argue against the diagnosis, and so do scaly lesions
Present for at least ten days - a rash of two days that fits otherwise does not yet qualify
The child is systemically well; this is a reaction to a virus, not the illness itself

Distribution

Cheeks, buttocks and the extensor surfaces of the forearms and legs, symmetrically. The validated criteria require at least three of those four sites. The distribution is the diagnosis: the trunk is characteristically spared, and extensive truncal lesions are one of the two features that argue against it. Most patients are young children, with adult cases reported.

Photographs

Gianotti-Crosti syndrome on a child's cheek. Monomorphous papules, all of one size and one age, scattered over the cheek - and the cheek is — Gianotti-Crosti syndrome on a child's cheek. **Monomorphous** papules, all of one size and one age, scattered over the cheek - and the cheek is one of the four sites the validated criteria count. Note what you cannot see here: the trunk, which should be spared. **The photographer records the diagnosis; this is not a peer-reviewed figure**, so weigh it as an illustration of the pattern rather than as a confirmed case. **This photograph is of light skin (Fitzpatrick III), and that is a limitation of this page rather than of the disease** - the monomorphous, flat-topped papules are palpable, and in darker skin palpation and distribution carry the diagnosis. Read the brown-and-black-skin description above as the primary guide; this page does not yet carry a photograph of this condition on darker skin.
Fitzpatrick III (Fitzpatrick type estimated from the photograph, not stated by the source) · Masryyy · Wikimedia Commons - Gianoti crosti new photo for diagnosis.jpg · CC BY-SA 4.0

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

Mimics

Hand, foot and mouth disease — Coxsackievirus A6 produces a Gianotti-Crosti-like pattern in around a third of atypical cases, so the two genuinely overlap
Eczema coxsackium and atypical hand, foot and mouth disease — The same outbreak strain; eczema coxsackium is vesiculobullous and erosive and settles on eczematous skin, rather than monomorphous and acral
Molluscum contagiosum — Also discrete papules in a well child, but umbilicated, asymmetrical, and appearing over months rather than in one crop
Scabies, including crusted scabies — Also papular and itchy in a small child, but with burrows, a different distribution and usually an affected household
Lichen planus — Also flat-topped papules, but violaceous, intensely itchy, typically flexural and with Wickham striae

What to do in the ED

Make the diagnosis on the distribution and the monomorphous lesions, and say so clearly - the value of this entry is a confident name, because the parents have usually been told it is an allergy
Examine for hepatomegaly and jaundice and ask about household hepatitis B. Test for hepatitis B where there is any risk factor or any hepatic sign, and consider Epstein-Barr virus serology where the history fits
Do not prescribe an antihistamine or a topical steroid reflexively. Neither changes the course; treat only if the child is genuinely itchy
Tell the family the expected duration explicitly: around three weeks is typical, but it can run much longer. A rash still present at six weeks is not a failure of treatment

Disposition

Discharge with a named diagnosis and GP follow-up. The rash itself needs nothing; the follow-up exists for the hepatitis B question and for the reassurance, which is the real intervention here.

Safety-netting

Return if the child becomes jaundiced, passes dark urine, develops abdominal pain, or becomes systemically unwell. The rash itself lasting weeks is expected and is not a reason to return - say that explicitly, because the duration is what brings these families back.

Sources

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