Exanthem

Exanthem is a skin eruption that appears with variable extension. It may present as small spots or papules distributed over different areas of the body or confined to a specific region.

The origin of exanthem is diverse, as it may be the manifestation of a viral or bacterial infectious disease, an autoimmune inflammatory condition, or an allergic reaction, most commonly to a medication. Determining the cause is essential to establish the most appropriate treatment; therefore, specialist evaluation of the rash should be performed as soon as possible.

In most cases, the prognosis of exanthem is favorable, and it resolves in a short period without complications. However, although uncommon, associated symptoms should be monitored, as the rash may occasionally indicate a medical emergency.

Symptoms

The hallmark symptom of exanthem is the appearance of a skin rash, typically reddish in color, although it may also appear pink, violet, purple, or brown. Different types of exanthem exist depending on their characteristics:

• According to lesion type, the eruption may consist of:
  • Macules (macular erythema): flat, discolored skin lesions smaller than one centimeter in diameter. They are clearly visible but do not show changes in skin texture or thickness.
  • Papules (papular exanthem): solid, raised skin lesions smaller than one centimeter in diameter. They contain no fluid.
  • Maculopapular exanthem: combination of macules and papules.
  • Erythema (erythematous exanthem): superficial skin inflammation accompanied by redness.
  • Wheals (urticarial exanthem): raised, erythematous skin lesions with a typically paler center. They cause intense itching.
  • Blisters or vesicles (bullous or vesicular exanthem): raised skin lesions filled with fluid.
  • Pustules (pustular exanthem): small superficial lesions filled with pus, usually inflamed.
  • Petechiae (petechial exanthem): small red, purple, or brown spots resulting from capillary rupture.
  • Ecchymosis: purplish, bluish, or yellowish discoloration caused by blood extravasation, commonly known as a bruise.

• According to distribution and location, exanthem may vary depending on lesion pattern and location:
  • Localized exanthem: confined to a specific body area.
  • Generalized exanthem: diffuse eruption covering large areas of the body.
  • Asymmetric exanthem: also known as asymmetric periflexural exanthem of childhood (APEC), common in children aged 4 to 5 years. It presents as eczema-like lesions in one axilla, groin, or elbow, unilaterally.
  • Centripetal exanthem: spreads from the extremities toward the center of the body (trunk, face, and neck).
  • Centrifugal exanthem: begins in the center of the body, usually the trunk, and spreads toward the periphery.
  • Cephalocaudal exanthem: starts on the head and spreads toward the trunk and extremities.
  • Flexural exanthem: appears in skin folds such as the axillae, groin, intergluteal region, interdigital spaces, inner elbow, or popliteal fossa (behind the knee).
  • Palmar exanthem: located on the palms of the hands.
  • Plantar exanthem: located on the soles of the feet.

• According to morphological pattern, describing eruption characteristics, shape, color, texture, and distribution:
  • Morbilliform exanthem: reddish or pinkish lesions, often slightly raised, measuring 3–10 mm. It begins on the face and behind the ears, then spreads to the chest, back, and extremities.
  • Rubelliform exanthem: similar to morbilliform, but lesions are smaller and do not coalesce.
  • Scarlet fever-like exanthem (scarlatiniform exanthem): rough, red, micropapular, and confluent rash; lesions tend to merge into large plaques.
  • Reticular exanthem: lesions form a net-like or mesh-like pattern.
  • Urticarial exanthem: small erythematous swellings causing intense itching.
  • Polymorphous exanthem: symmetrical distribution across the body; lesions are raised, red, and target-shaped (concentric pattern).

The exanthem may be accompanied by other symptoms of varying severity, such as:

• Fever.
• Pruritus (itching).
• Ocular involvement, such as conjunctivitis or uveitis.
• Mucosal involvement: lesions affecting at least two mucosal sites (anus, conjunctiva, mouth).
• Respiratory symptoms: rhinitis, pharyngitis, tonsillitis, pharyngotonsillitis.
• Digestive symptoms: abdominal pain, vomiting, diarrhea.
• Lymphadenopathy: lymph node enlargement.
• Hepatosplenomegaly: enlargement of the liver and spleen.
• Edema: swelling due to fluid accumulation.
• Arthritis: stiffness, inflammation, pain, and joint tenderness.
• Meningeal signs: indicating irritation of the meninges (membranes covering the brain and spinal cord), representing a serious condition requiring urgent medical attention:
• Neck stiffness.
• Severe headache.
• Kernig sign: resistance to knee extension and lumbar pain when lying supine with the hip flexed at 90°.
• Brudzinski sign: involuntary flexion of hips and knees when flexing the neck while lying supine.

• Signs of shock: medical emergency presenting with sudden rash onset, high fever, hypotension, nausea, vomiting, altered mental status, cold skin, sweating, and possibly fainting or lethargy.
• Pathognomonic signs: disease-specific symptoms sufficient to establish a diagnosis on their own.

Causes

Exanthem may be caused by a wide range of diseases, including:

• Viral infections: the most common cause of exanthem.

• Roseola infantum: caused by human herpesvirus type 6. Common in children under two years. Characterized by a sudden pink skin rash.
• Measles: transmitted via respiratory droplets. Caused by a virus of the Paramyxoviridae family (genus Morbillivirus). Produces a non-pruritic reddish exanthem starting on the face and spreading to trunk and extremities.
• Rubella: caused by Rubivirus of the Togaviridae family. Rash starts on the face and spreads after fading; pink, non-pruritic lesions.
• Erythema infectiosum: also called fifth disease, caused by parvovirus B19. Rash mainly affects the cheeks.
• Hand-foot-and-mouth disease: common in pediatrics, caused by enteroviruses, usually Coxsackie A16. Painful oral blisters and rash on hands and feet.
• Mononucleosis: caused by Epstein–Barr virus, transmitted via saliva. Morbilliform pink/red exanthem, typically on the trunk.
• Cytomegalovirus infection: common virus; usually asymptomatic in healthy individuals but severe in pregnant or immunocompromised patients. Rash similar to measles with macules and papules starting on the face and spreading.
• Enterovirus infection: common in childhood, especially summer and autumn. Causes maculopapular rash on face, trunk, and extremities.

• Bacterial infections:

• Scarlet fever: caused by Streptococcus pyogenes. Bright red, rough, non-pruritic rash, more common between ages 5 and 15.
• Lyme disease: caused by Borrelia burgdorferi. Produces a target-like lesion (erythema migrans).
  • Allergies: drug-induced exanthem may appear immediately or after several days. Depending on the trigger (usually medication), it may present as rash, wheals, or scaly plaques.
  • Scabies: caused by the mite Sarcoptes scabiei, which burrows into the skin to lay eggs. Causes irritation, vesicles, and intense itching.
  • Lupus: systemic lupus erythematosus causes a butterfly-shaped facial rash across the cheeks and nose.

Risk factors

Risk factors vary depending on the underlying disease, but common ones include:

• Age: conditions causing exanthem are more frequent in children under 4 years.
• Close contact with individuals with infectious disease.
• Lack of immunization (missing recommended vaccines).
• Immunosuppression.
• Previous streptococcal or Epstein–Barr virus infection.
• New medication use, which may trigger allergic reactions.

Complications

Exanthem may lead to superinfection of lesions, especially if vesicles rupture and scabs form. Other complications depend on the underlying disease and include:

• Febrile seizures: tremors and spasms due to fever >38°C.
• Joint pain.
• Encephalitis: inflammation of the brain (central nervous system).
• Pericarditis: inflammation of the pericardium surrounding the heart.
• Arthritis: joint inflammation, pain, and stiffness.
• Pneumonia: lung infection causing alveolar inflammation.
• Glomerulonephritis: inflammation of renal glomeruli.
• Rheumatic fever: severe inflammatory disease affecting skin, joints, heart, and brain following untreated streptococcal infection.
• Aseptic meningitis: meningitis not caused by bacterial infection, generally with favorable prognosis.
• Meningococcemia: bloodstream infection caused by Neisseria meningitidis, potentially leading to sepsis and systemic inflammatory response.

Which specialist treats exanthem?

Exanthematous diseases are typically managed by Pediatrics, Medical-surgical dermatology and Venereology, Internal medicine, Allergology, or Infectious diseases specialists.