Childhood Exanthems: Introduction - Rash Decisions & Red Alerts
- Exanthem: Diffuse skin eruption. Enanthem: Mucosal eruption.
- Key History: Prodrome (nature, duration), fever (pattern, height), contacts (sick, travel), immunization.
- Rash Morphology: Macular (flat), papular (raised), vesicular (fluid-filled), petechial (non-blanching).
- Distribution Patterns: Cephalocaudal (head-to-toe), centrifugal (trunk to extremities), centripetal (extremities to trunk).
⭐ Koplik's spots, pathognomonic for measles, are bluish-white spots on an erythematous base on the buccal mucosa, appearing 1-2 days before the rash.
Childhood Exanthems: Measles & Rubella - Dotty Dilemmas & Fever Fits
| Feature | Measles (Rubeola) | Rubella (German Measles) |
|---|---|---|
| Etiology | Paramyxovirus | Togavirus |
| Prodrome | Fever, 3 C's (Cough, Coryza, Conjunctivitis) 📌; 3-5 days | Mild fever, lymphadenopathy; 1-5 days |
| Rash | Maculopapular; cephalocaudal; lasts 5-7 days; desquamates | Maculopapular; cephalocaudal; rapid (1-3 days); '3-day measles' 📌 |
| Key Signs | Koplik's spots (buccal)  | Forchheimer spots (palate) |
| Complications | Otitis media, pneumonia, encephalitis (SSPE) | Arthralgia/arthritis, thrombocytopenia, CRS |
| Prevention | MMR vaccine | MMR vaccine |
Childhood Exanthems: Parvo B19, HHV-6, VZV - Cheeky Slaps & Rosy Pox
| Feature | Erythema Infectiosum (Fifth Disease) | Roseola Infantum (Sixth Disease) | Varicella (Chickenpox) |
|---|---|---|---|
| Etiology | Parvovirus B19 | HHV-6 (Human Herpesvirus 6), HHV-7 | Varicella-Zoster Virus (VZV) |
| Prodrome | Mild fever, malaise, headache | High fever (3-5 days), otherwise well | Fever, malaise, pharyngitis, anorexia |
| Rash | 1. Bright red "slapped cheek" rash 2. Erythematous macular/morbilliform rash on trunk/limbs 3. Lace-like reticular pattern as rash fades | Maculopapular rash appears as fever subsides (exanthem subitum); starts on trunk, spreads to face/extremities | Crops of intensely pruritic vesicles on erythematous base ("dew drop on rose petal"); various stages present simultaneously; starts on trunk/face, spreads centrifugally |
| Complications | Aplastic crisis (in hemolytic anemia), arthralgia/arthritis (adults), hydrops fetalis (pregnancy) | Febrile seizures | Secondary bacterial infection, pneumonia, encephalitis, Reye's syndrome (aspirin use ⚠️) |
⭐ Roseola Infantum (HHV-6/7) is characterized by high fever for 3-5 days in an otherwise well child, followed by rash appearance as the fever abruptly subsides (exanthem subitum).
📌 Varicella = Vesicles in Various stages
Childhood Exanthems: Coxsackie, Strep, Kawasaki - Handfuls & Strawberry Tongues
- Hand, Foot, Mouth Disease (HFMD):
- Etiology: Coxsackie A viruses, Enterovirus 71.
- Rash: Oral ulcers; vesicular lesions on hands, feet, buttocks.
- Scarlet Fever:
- Etiology: Group A Streptococcus (GAS).
- Rash: Sandpaper texture, Pastia's lines, strawberry tongue, circumoral pallor.
- Treatment: Penicillin.
- Kawasaki Disease:
- Diagnostic Criteria: Fever (Burn) ≥ 5 days + ≥4 CRASH 📌 (Conjunctivitis, Rash, Adenopathy, Strawberry tongue, Hand/feet changes).
- Complications: Coronary artery aneurysms.
- Treatment: IVIG (2g/kg), Aspirin.
⭐ Kawasaki Disease is the leading cause of acquired heart disease in children in developed countries; timely administration of IVIG (ideally within 10 days of fever onset) significantly reduces the risk of coronary artery aneurysms from ~25% to <5%.
High‑Yield Points - ⚡ Biggest Takeaways
- Measles: Koplik's spots (pathognomonic), cephalocaudal rash, risk of SSPE.
- Rubella: Forchheimer spots, milder rash, Congenital Rubella Syndrome risk.
- Erythema Infectiosum (Fifth Disease): Parvovirus B19, "slapped cheeks", then lacy reticular rash.
- Roseola Infantum: HHV-6/7, high fever then rash post-defervescence.
- Hand, Foot, Mouth Disease: Coxsackievirus A, oral, palmar, plantar vesicles.
- Kawasaki Disease: Fever >5 days, mucocutaneous signs, coronary artery aneurysm risk.
- Scarlet Fever: Group A Strep toxin, sandpaper rash, strawberry tongue, Pastia's lines.
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