OVERVIEW

What is pediatric papular acrodermatitis?

Pediatric papular acrodermatitis is also known as Gianotti-Crosti syndrome, childhood papular acrodermatitis, or papular acrodermatitis.

Gianotti first described this condition in 1955, and Crosti and Gianotti revisited it in 1957.

As the name suggests, this rash presents as symmetrical papules primarily distributed on the extremities, such as the cheeks, buttocks, forearms, and extensor surfaces of the lower legs.

Pediatric papular acrodermatitis generally does not require active intervention, as the rash typically resolves spontaneously, lasting anywhere from 10 days to 6 months.

At what age does pediatric papular acrodermatitis primarily occur?

Pediatric papular acrodermatitis mainly affects children under 5 years old.

During childhood, the incidence is roughly equal between boys and girls. In fact, older children, adolescents, and even adults can also develop this condition.

SYMPTOMS

What are the symptoms of infantile papular acrodermatitis?

Many children experience discomfort in the nose, throat, or gastrointestinal tract (prodromal symptoms) about 1 week before the rash appears, which may have resolved by the time the rash develops.

The typical skin manifestations include:

• Sudden appearance of dense, small rashes, mainly tiny bumps (papules), sometimes with fluid inside (papulovesicles).
• Symmetrically distributed, uniform in shape, flat-topped, pinkish-brown lesions measuring 1–10 mm in diameter, which may merge to form plaques.
• Occasionally, the rash may show signs of bleeding. In the early stages, lesions resembling trauma may appear, known as the "Koebner phenomenon."
• Itching is usually mild to moderate but may be absent or, in some cases, severe.
• The rash primarily affects the face, buttocks, extensor surfaces of the forearms and lower legs, and feet. The trunk (chest, abdomen, and back) is also commonly involved, though the rash there tends to resolve faster and is less dense than on the extremities. Mucous membranes (e.g., oral mucosa) and nails are typically unaffected.

In addition to skin symptoms, some children may experience:

• General malaise, low-grade fever, diarrhea, and swollen lymph nodes (mainly in the neck, armpits, or groin).
• Hepatitis may occur, though its incidence is unclear. If present, it is usually mild and does not lead to jaundice (yellowing of the skin and whites of the eyes). Enlargement of the spleen may also occur but is uncommon.
• Rarely, spleen enlargement may be observed.

CAUSES

What causes infantile papular acrodermatitis?

Infantile papular acrodermatitis is associated with viral infections, most commonly hepatitis B virus and EB virus. Other less common viruses include enterovirus, cytomegalovirus, parvovirus, parainfluenza virus, hepatitis A virus, rotavirus, molluscum contagiosum virus, respiratory syncytial virus, HIV, human herpesvirus 6, Mycoplasma pneumoniae, β-hemolytic streptococcus, Bartonella henselae, and Borrelia burgdorferi.

Data shows that about 1/5 of infantile papular acrodermatitis cases are caused by hepatitis B virus, while 1/2 to 3/4 are caused by EB virus.

Additionally, infantile papular acrodermatitis may occur after vaccination, though reports are rare. Possible vaccines include influenza vaccine, MMR vaccine, hepatitis B vaccine, measles vaccine, oral polio vaccine, hepatitis A vaccine, and Japanese encephalitis vaccine.

The exact mechanism by which viruses or vaccines trigger infantile papular acrodermatitis is unclear. One possible explanation is that infection or vaccination induces a high T-cell reactivity in the body, leading to an abnormal immune response that causes the rash.

The clinical manifestations of infantile papular acrodermatitis may represent a common endpoint for several viral infections. One hypothesis suggests that this clinical presentation results from a delayed-type hypersensitivity reaction triggered by viral infection.

Is infantile papular acrodermatitis contagious?

Not necessarily.

Whether the rash is contagious depends on the underlying cause, such as the specific viral infection. However, in most cases, the rash itself is no longer contagious once it appears.

In fact, most children with infantile papular acrodermatitis can continue attending daycare or school without isolation.

Children who are hepatitis B surface antigen-positive can also attend daycare or school without special restrictions, provided they do not exhibit aggressive behaviors like biting.

Is infantile papular acrodermatitis hereditary?

No.

DIAGNOSIS

Is it necessary to undergo tests to diagnose infantile papular acrodermatitis?

In most cases, no tests are required. Experienced doctors can diagnose it by asking basic questions and examining the rash, which is called a clinical diagnosis.

Laboratory tests are not helpful for confirming this condition. However, tests may assist in identifying specific causes or ruling out other diseases.

Possible tests include skin biopsy, liver function tests, hepatitis B tests, and other viral tests. For example, if the rash is atypical, a skin biopsy may be needed to exclude other conditions. If there is a high risk of hepatitis B infection or hepatomegaly, liver function and hepatitis B tests may be performed.

Which diseases can be confused with infantile papular acrodermatitis? How to differentiate them?

Typical infantile papular acrodermatitis is relatively easy to diagnose.

In atypical cases, it needs to be distinguished from the following diseases. Key distinguishing features include the onset, duration, distribution, color of the rash, presence and severity of itching, and whether mucous membranes or nails are involved.

Professional dermatologists are often required to differentiate them clearly. Below is a summary of the characteristics of related diseases:

• Erythema infectiosum: A common childhood rash caused by a viral infection. The rash starts on the cheeks and spreads to the limbs, usually appearing as patches (small flat red spots) rather than papules.
• Erythema multiforme: Primarily occurs in adolescents and young adults, with a small proportion in children. It may be associated with herpes simplex virus or mycoplasma infection. Early papules may appear, but the typical rash shows target lesions—centrally depressed, darker in color, sometimes with blisters or purpura. Some may also have mucosal involvement.
• Hand, foot, and mouth disease: Mainly caused by coxsackievirus, commonly seen in children under 5. Symptoms include fever, blisters on the oral mucosa and tongue, and small, fragile blisters on the hands, feet, buttocks, and genitals. The rash usually resolves within 7–10 days.
• Scabies: A contagious disease caused by scabies mites (a parasite). It causes intense itching, more severe than infantile papular acrodermatitis. The rash consists mainly of papules and can appear anywhere on the body.
• Papular urticaria: Also known as hypersensitivity to insect bites (e.g., fleas, mosquitoes, bedbugs, mites), leading to chronic or recurrent papules, vesicles, target lesions, or wheals. The rash is symmetrical, often grouped or clustered on exposed areas, and may take weeks to years to resolve.
• Frictional lichenoid eruption: A type of dermatitis caused by friction from rough surfaces like outdoor ground, sand, carpets, or coarse wool rugs during crawling or play. In China, it is also called "sand dermatitis." It mainly affects the back of the hands and wrists, followed by the buttocks, knees, face, and neck. Severe cases may spread widely, with varying degrees of itching and usually no systemic symptoms. It typically resolves on its own within weeks.

TREATMENT

Which department should be consulted for infantile papular acrodermatitis?

Dermatology.

How is infantile papular acrodermatitis treated?

Infantile papular acrodermatitis usually resolves spontaneously without active intervention. The rash typically lasts 10 days to 6 months, though durations of 5 days to 12 months have also been reported. The only necessary treatment is to relieve itching symptoms.

• For mild itching, use topical emollients;
• For moderate itching, apply topical calamine lotion;
• For severe itching, administer a single dose of sedating antihistamines at night, such as chlorpheniramine maleate tablets, cyproheptadine hydrochloride tablets, ketotifen fumarate tablets, or diphenhydramine.
  Topical corticosteroids like desonide, hydrocortisone butyrate, or mometasone furoate may also be tried, though there is no evidence that this therapy alters the disease course. Nevertheless, it may help control itching.

If infantile papular acrodermatitis is caused by hepatitis B virus infection, regular follow-up examinations are recommended. In cases of acute HBV infection that resolves without progressing to chronic infection, serum aminotransferase (a liver function marker) typically normalizes within 1–4 months. Persistent elevation of serum alanine aminotransferase (ALT) beyond 6 months suggests chronic hepatitis.

DIET & LIFESTYLE

What should be noted in the diet for infantile papular acrodermatitis?

Infantile papular acrodermatitis is unrelated to diet. Diet does not worsen the condition nor does it help improve the disease.

What should be noted in daily life for infantile papular acrodermatitis?

There are no special precautions. As mentioned above, in most cases, it is generally believed that the rash is no longer contagious once it appears. Therefore, affected children can usually continue attending daycare or school.

PREVENTION

How to prevent pediatric papular acrodermatitis?

Pediatric papular acrodermatitis has no clear association with daily life factors, so there is no effective prevention method.