Atlas of Exanthems

🦠 Viral Outbreaks

Generally self-limited and with systemic symptoms. Remember: ineffective antibiotics. Isolation according to pathology.

Measles ▶

Clinic & Tips: Confluent, morbilliform maculopapular rash. It starts on the face (hairline) and extends cephalocaudally. Prodromes: High fever (>40°C), cough, coryza, conjunctivitis. Koplik spots: Grayish-white papules on the buccal mucosa (2-3 days before the rash).

Management: Symptomatic. Respiratory isolation (droplets/air) for 4 days from the onset of the rash. Vitamin A recommended by WHO in cases of risk/deficiency.

Prevention: Triple viral vaccine (MMR). Highly contagious.

Rubella ▶

Clinic & Tips: Dotted, non-confluent reddish/pink rash (lasts ~3 days). Rapid cephalocaudal extension. Prodromes: Mild. Highlights the generalized lymphadenopathy (especially retroauricular and suboccipital). Forchheimer spots: Petechiae on soft palate.

Management: Symptomatic.

Risk: Highly teratogenic (Congenital Rubella Syndrome) in susceptible pregnant women. Prevention with SRP.

Chickenpox ▶

Clinic & Tips: Very pruritic polymorphic rash: coexistence of macules, papules, vesicles ("dewdrop") and crusts -> Pattern of "starry sky". It starts on the face/scalp and goes down to the trunk.

Management: Symptomatic (oatmeal baths, calamine, acetaminophen). Avoid Aspirin/Ibuprofen (risk of Reye's Syndrome and necrotizing fasciitis). Acyclovir only in risk groups if started <24 hours.

Prevention: Contagious until ALL lesions are in the scabbing phase. Vaccine available.

Infectious Erythema (5th Disease) ▶

Clinic & Tips: Parvovirus B19. Exanthem in 3 phases: 1) "Slapped Cheek" (intense facial erythema with perioral pallor). 2) Reticular rash (lace) on trunk and extremities. 3) Fluctuating with heat/sun.

Management: Symptomatic. Care in patients with hemolytic anemia (risk of aplastic crisis) and pregnant women (hydrops fetalis).

Contagion: When the rash appears, the child it is no longer contagious and can go to school.

Roseola (Sudden Exanthema / 6th Enf.) ▶

Clinic & Tips: VHH-6. Typical in infants. Very high fever (39-40°C) for 3-5 days. Diagnostic key: Pink maculopapular rash appears abruptly when the fever subsides. Starts in trunk.

Management: Rigorous thermal control (frequent cause of febrile seizures). Reassure parents.

Sick Hands, Feet and Mouth ▶

Clinic & Tips: Coxsackie A16 / Enterovirus. Painful oral sores (enanthem). Oval vesicles/papules with an erythematous base on the palms, soles, gluteal and perioral areas.

Management: Analgesia (ibuprofen/paracetamol). Main risk: Dehydration due to refusal to eat due to oral pain. Offer cold/iced liquids.

Molluscum Contagiosum ▶

Clinic & Tips: Poxvirus. Firm, pearly, dome-shaped papules with central umbilication. Generally asymptomatic, grouped in folds or trunk. Autoinoculable by scratching.

Management: Expectant management (spontaneous resolution in months/years). Cryotherapy or curettage if there is discomfort or for aesthetic reasons (refer to dermatology).

Papular acrodermatitis (Gianotti-Crosti) ▶

Clinic & Tips: Paraviral reaction (HBV, EBV, Coxsackie). Monomorphic micropapules, skin/copper color. Acral and Symmetrical Distribution: Face, glutes, limb extensors. Respect the trunk.

Management: Self-limited, but long-lasting (weeks to months). Antihistamines only if there is pruritus.

Unilateral Laterothoracic Rash ▶

Clinic & Tips: Probable viral etiology. Erythematous-papular rash unilateral. It begins in the axillary or lateral fold of the chest and extends to the ipsilateral arm/flank. Respect face, palms and soles.

Management: Benign and self-limited evolution (4-6 weeks). Skin hydration.

🔬 Bacterial Outbreaks

Infections requiring targeted antibiotic therapy. Generally secondary to disruption of the skin barrier.

Scarlet fever ▶

Clinic & Tips: *Streptococcus pyogenes*. Erythematous micropapular rash (touch of "sandpaper"). Pastia Lines in folds (hyperpigmentation). Filatov triangle: perioral pallor. raspberry tongue. Previous/concomitant purulent pharyngotonsillitis.

Management: Oral Amoxicillin or Penicillin V for 10 days to prevent non-suppurative complications (Rheumatic Fever).

Evolution: Late generalized or glove/sock peeling at 1-2 weeks.

Impetigo ▶

Clinic & Tips: S. aureus / S. pyogenes. Non-bullous form (scabs meliceric, perioral/nasal) and bullous (flaccid vesicles that leave collar erosion).

Management: Mupirocin or topical Fusidic Acid for localized forms. Oral Cephalexin or Amoxicillin/Clavulanate if extensive or blistering.

Cellulitis ▶

Clinic & Tips: Erythematous, edematous, hot and painful plaque. Poorly defined edges. Deep infection of the dermis and subcutaneous cellular tissue.

Management: Systemic antibiotics (Cephalexin/Clindamycin). Emergency Care: IV admission if there is facial (periorbital) involvement, rapid progression, signs of sepsis or a young infant.

Staphylococcal Scalded Skin Syndrome ▶

Clinic & Tips: Caused by exfoliative exotoxin of S. aureus. Generalized painful erythema, followed by large flaccid blisters and extensive peeling. Positive Nikolsky sign. Radial perioral scabs.

Management: Pediatric hospital/ICU admission. Fluid therapy (management such as major burn), analgesia and IV antibiotic therapy (Cloxacillin, Cefazolin, Vancomycin).

🫀 Systemic / Vascular

Pathologies with significant systemic involvement or vasculitis. Differential diagnosis in emergencies is vital.

Kawasaki disease ▶

Clinic (Diagnostic criteria): Persistent high fever >5 days + 4 of 5 criteria: 1) Non-exudative bilateral conjunctival injection. 2) Oropharyngeal changes (cleft lips, strawberry tongue, hyperemic pharynx). 3) Cervical lymphadenopathy (>1.5cm, unilateral). 4) Polymorphic rash (trunk, accentuated in perineum). 5) Peripheral changes (erythema/indurated edema in hands/feet, late periungual peeling).

Risk: Coronary artery aneurysms (main cause of acquired heart disease in children).

Management in Emergencies: Income. Intravenous gamma globulin (IVIG) in the first 10 days + Aspirin at anti-inflammatory doses. Baseline echocardiogram.

Schönlein-Henoch purple ▶

Clinic & Tips: IgA vasculitis. Palpable purple non-thrombocytopenia predominantly in the lower limbs (declining areas) and buttocks. Classic triad: Purpura, Arthritis/Arthralgia, and Abdominal pain (colic type).

Emergency Risk: Renal involvement (microhematuria, proteinuria) and intestinal intussusception.

Management: Rest, NSAIDs (if there is no GI bleeding or significant kidney involvement). Systemic corticosteroids if there is severe abdominal pain. Mandatory blood pressure measurement and urine test strip.

Erythema Multiforme ▶

Clinic & Tips: Hypersensitivity reaction (infections: HSV, Mycoplasma; or drugs). Pathognomonic lesions in bullseye or target shooting (dark center, pale halo, erythematous ring). Symmetrical, acral, palms and soles. There may be mild mucosal involvement (EM Minor).

Management: Remove trigger. Topical/systemic antihistamines. If there is great mucosal/systemic involvement, think about SJS/TEN.

🍄 Fungal and Parasitic

They require strict environmental management in addition to etiological treatment.

Body Ringworm ▶

Clinic: Pruritic annular plaque with scaly active edge and clear center.
Treatment: Topical antifungals (Terbinafine, Clotrimazole). Oral griseofulvin if it is Tinea capitis.

Scabies (Scabies) ▶

Clinic: Intense nocturnal itching. Acrine furrows, papules in folds, armpits, navel and interdigital areas. In infants it affects the palms, soles and head.
Treatment: Permethrin 5% (topical, whole family) or oral Ivermectin. Washing clothes at 60°C.

Diaper Thrush ▶

Clinic & Tips: Bright red erythematous plaque in the diaper area. Key information: It affects the inguinal folds (unlike irritant dermatitis) and presents satellite injuries peripherals.

Management: Topical antifungals (Nystatin, Clotrimazole, Miconazole). Keep the area dry and change the diaper frequently.

Pityriasis Versicolor ▶

Clinic & Tips: Caused by Malassezia furfur. Hypo- or hyperpigmented macules with fine peeling (fingernail sign), mainly on the trunk and arms. Common in adolescents (warm/humid climates).

Management: Topical antifungals (Ketoconazole Shampoo, Selenium Sulfide). He warns that skin repigmentation will take months.

🔥 Inflammatory and Allergic

Urticaria ▶

Clinic: Very pruritic, migratory and evanescent erythematous hives (<24 hours each lesion). Alert: Always look for signs of anaphylaxis or angioedema (airway).
Treatment: 2nd generation H1 antihistamines. Corticosteroids if there is severe angioedema.

Atopic Dermatitis ▶

Clinic: Xerosis, intense itching. In infants: cheeks, extensors. In schoolchildren: flexures (antecubital, popliteal).
Treatment: Continuous emollients. Topical corticosteroids in outbreaks.

Contact Dermatitis ▶

Clinic & Tips: Eczematous plaques, vesicles or blisters in acute cases. Key information: The lesion is geographically limited to the area of contact with the irritant or allergen (metals, plants, topicals).

Management: Initial washing of the area, avoid the causal agent. Topical corticosteroids of medium/high potency depending on location. Antihistamines for pruritus.

Diaper Rash (Irritative) ▶

Clinic & Tips: Confluent erythema on convex surfaces (buttocks, genitals, lower thighs) in direct contact with the diaper (feces/urine). Key information: Respect the deep folds.

Management: Barrier pastes (Zinc oxide, Lassar). Frequent diaper change, leave it open if possible. If it lasts >3 days or affects folds, suspect superinfection due to Candida.

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Summary and Differential Diagnosis

Pathology	Agent/Etiology	Characteristics of the Exanthema	Key Signs/Prodromes
Measles	Paramyxovirus	Maculopapular confluent, cephalocaudal.	Very high fever, triple cold, Koplik spots.
Rubella	Togavirus	Dotted pink, not confluent. Cephalocaudal (3 days).	Retroauricular/suboccipital lymphadenopathy.
Chickenpox	Varicella-Zoster Virus	Pruritic vesicles in different stages ("starry sky").	Intense itching, lesions on the mucous membranes and scalp.
Infectious Erythema	Parvovirus B19	"Slapped cheek" -> reticular pattern on trunk.	Fluctuates with temperature/sun. It no longer infects when it sprouts.
Children's Roseola	VHH-6/7	Pink spots on trunk, centrifugal spread.	Appears just after the high fever subsides (3-5 days).
Hands, Feet and Mouth	Coxsackie A16/Enterovirus	Vesicles/papules on palms, soles and buttocks.	Painful sores in the mouth (enanthem), refusal to eat.
Molluscum Contagiosum	Poxvirus	Pearly, firm papules, with central umbilication.	Asymptomatic, grouped in folds, autoinoculatable.
Gianotti-Crosti	Paraviral Reaction	Monomorphic micropapules, skin/copper color.	Distribution acral and symmetrical. Respect the trunk.
Laterothoracic rash	Likely Viral	Erythematous-papular onset unilateral.	Starts in the armpit/thorax, extends to the arm/flank.
Scarlet fever	S. pyogenes	Punctate, bright red, "sandpaper" feel.	Previous tonsillitis, Pastia Lines, Strawberry Tongue.
Impetigo	S. aureus / S. pyogenes	Scabs meliceric or flaccid vesicles (bullous).	Frequent perioral/nasal distribution, autoinoculatable.
Cellulitis	Deep skin bacteria	Erythematous, edematous, hot and painful plaque.	Poorly defined borders, risk of progression and sepsis.
Scalded Skin Scam.	S. aureus exotoxin	Erythema, large flaccid blisters and peeling.	Nikolsky sign (+), extreme generalized pain.
Sick Kawasaki	Vasculitis (Unknown)	Polymorphic, accentuated in the perineal area.	Fever >5 days, conjunctivitis, strawberry tongue, hand/foot edema.
Father Schönlein-Henoch	IgA vasculitis	Palpable purple in lower limbs/buttocks.	Colicky abdominal pain, arthralgia, kidney involvement.
Erythema Multiforme	Hypersensitivity	Pathognomonic lesions in bullseye (target shooting).	Symmetrical acral involvement (palms/soles). Associated with VHS/drugs.
Body Ringworm	Dermatophytes (Fungi)	Annular plate with clear center and scaly active edge.	Pruritic, asymmetrical, scaly.
Scabies (Scabies)	Sarcoptes scabiei	Acrine furrows, papules in folds and interdigital areas.	Intense nocturnal itching, family history of scratching.
Diaper Thrush	Candida albicans	Bright red erythema with satellite injuries.	Affects the inguinal folds (vs. irritative).
Pityriasis Versicolor	Malassezia furfur	Hypo/hyperpigmented macules with fine peeling.	Fingernail sign. It gets worse in summer/heat.
Urticaria	Allergic / Idiopathic	Pruritic erythematous hives.	Migratory injuries and evanescent (<24h). Monitor anaphylaxis.
Atopic Dermatitis	High skin barrier	Very itchy eczematous plaques, xerosis.	It affects extensors (infants) or flexures (schoolchildren).
Contact Dermatitis	Irritant/Allergen	Eczematous or vesicular plaques.	Injury geographically delimited to the contact zone.
Irritative Dermatitis (Diaper)	Feces/Urine/Friction	Erythema in convex areas of the diaper.	Respect the folds deep inguinals.

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Emergency Quiz

1. A 10-month-old infant arrives at the emergency room. Mother reported 4 days of fever of 39.5°C that was difficult to control, which suddenly disappeared today, at which time a pink maculopapular rash appeared on the trunk. Most likely diagnosis:

Measles Roseola (Sudden Exanthema) Infectious Erythema

2. A 6-year-old schoolboy presents with a sore throat and an erythematous rash that feels like "sandpaper" to the touch, with marked erythema in the axillary folds (Pastia Lines). Treatment of choice:

Ibuprofen and high (it's viral) oral acyclovir Amoxicillin or Penicillin V oral

3. 3-year-old boy with fever for 6 days, red eyes without discharge, lip fissures, strawberry tongue, and a 2cm unilateral cervical lymph node. Main complication to avoid:

Coronary artery aneurysms (Kawasaki disease) Acute kidney failure (Schönlein-Henoch) Rheumatic Fever (Scarlet Fever)

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Attention in Critics Box

Red flags in the emergency department suggesting life-threatening pathologies.

Non-bleachable rash

Petechiae or purpura fulminans under vitro pressure. High suspicion of meningococcemia, sepsis or DIC.

Airway Commitment

Sudden urticaria + wheezing, stridor, angioedema or hypotension. Anaphylaxis. Urgent IM adrenaline.

Severe Mucocutaneous Involvement

Extensive epidermal peeling (Nikolsky +), involvement of ≥2 mucous membranes, high fever. Suspected SJS/NET.