Differential Diagnoses for Pediatric Conditions
Erythema Infectiosum (Fifth Disease)
The three key differential diagnoses for erythema infectiosum are scarlet fever, roseola, and erythema multiforme.
- Scarlet fever presents with a sandpaper-textured rash during active fever (not after defervescence), pharyngeal erythema, tonsillar exudates, and spreads from upper trunk throughout the body while sparing palms and soles 1, 2
- Roseola shows a maculopapular rash that appears only after fever resolution (3-5 days of high fever), primarily in infants 6 months to 3 years, with the rash sparing palms, soles, face, and scalp 1, 3
- Erythema multiforme displays characteristic raised target or iris lesions distributed symmetrically on extremities and trunk, often triggered by HSV or Mycoplasma pneumoniae infection, with possible mucosal involvement 4, 5, 6
The distinguishing feature of erythema infectiosum is the "slapped cheek" appearance on the face followed by a lacy, reticulated rash on trunk and extremities that spares palms and soles, occurring in school-aged children (4-10 years) 7, 3.
Erythema Multiforme
The three key differential diagnoses for erythema multiforme are Stevens-Johnson syndrome, erythema infectiosum, and drug eruptions.
- Stevens-Johnson syndrome (SJS) involves extensive skin involvement with significant morbidity (5-15% mortality), typically two or more mucous membranes affected, systemic symptoms, and is usually drug-induced rather than infection-triggered 6
- Erythema infectiosum presents with "slapped cheek" facial erythema and lacy reticulated rash on extremities, but lacks the characteristic target lesions and mucosal involvement seen in EM 7, 3
- Drug eruptions present as fine reticular maculopapular rashes or broad, flat erythematous macules without the pathognomonic target or iris lesions that define erythema multiforme 2
The hallmark of erythema multiforme is the presence of typical or atypical raised target lesions distributed symmetrically on acral surfaces (extremities), often with mucosal involvement, most commonly triggered by HSV or Mycoplasma pneumoniae 4, 5, 6.
Roseola (Roseola Infantum)
The three key differential diagnoses for roseola are scarlet fever, erythema infectiosum, and Kawasaki disease.
- Scarlet fever develops a sandpaper-textured rash during active fever (not after defervescence), includes pharyngeal findings with tonsillar exudates, and requires antibiotic therapy to prevent complications 1, 2
- Erythema infectiosum occurs in older children (4-10 years vs. 6 months-3 years for roseola), presents with "slapped cheek" appearance, and shows a lacy reticulated pattern rather than simple maculopapular rash 7, 3
- Kawasaki disease requires fever ≥5 days plus 4 of 5 criteria (conjunctival injection, oral changes, lymphadenopathy, extremity changes, polymorphous rash), has truncal rash with groin accentuation, and carries risk of coronary artery aneurysms if untreated 8, 9
The pathognomonic feature of roseola is high fever lasting 3-5 days followed by appearance of maculopapular, pink-to-rose-colored rash upon defervescence in infants 6 months to 3 years, with the rash sparing palms, soles, face, and scalp 1, 3.
Atypical Mycobacterial Disease
The three key differential diagnoses for atypical mycobacterial disease are tuberculosis, cat-scratch disease (Bartonella), and bacterial lymphadenitis.
- Tuberculosis presents with chronic lymphadenitis (often cervical), systemic symptoms including night sweats and weight loss, positive tuberculin skin test or interferon-gamma release assay, and requires multi-drug therapy 8
- Cat-scratch disease shows regional lymphadenopathy following cat scratch or bite, typically resolves spontaneously, and can be confirmed with Bartonella serology 8
- Bacterial lymphadenitis (Staphylococcus/Streptococcus) presents with acute onset, tender, warm, erythematous lymph nodes, systemic signs of infection, and responds rapidly to antibiotics 8
Atypical mycobacterial disease typically presents with chronic, painless, unilateral cervical or submandibular lymphadenitis in children 1-5 years old, with violaceous skin discoloration overlying the node, minimal systemic symptoms, and negative tuberculin skin test or small reaction (<15mm) 8.
Encopresis
The three key differential diagnoses for encopresis are Hirschsprung disease, spinal cord abnormalities, and hypothyroidism.
- Hirschsprung disease presents with delayed passage of meconium in newborn period, chronic constipation from birth, failure to thrive, and requires rectal biopsy showing absence of ganglion cells for diagnosis 8
- Spinal cord abnormalities (tethered cord, spina bifida occulta) show neurologic findings including decreased lower extremity reflexes, abnormal gait, sacral dimple or hair tuft, and bladder dysfunction alongside bowel symptoms 8
- Hypothyroidism manifests with constipation plus other systemic signs including growth delay, cold intolerance, dry skin, bradycardia, and abnormal thyroid function tests 8
Functional encopresis (most common) presents with fecal soiling in children >4 years old, history of chronic constipation with overflow incontinence, palpable fecal mass on abdominal examination, and normal neurologic examination 8.
Respiratory Syncytial Virus (RSV)
The three key differential diagnoses for RSV bronchiolitis are influenza, human metapneumovirus, and bacterial pneumonia.
- Influenza presents with more prominent systemic symptoms (high fever, myalgias, headache), can cause encephalopathy or focal neurologic signs (especially H1N1), and requires specific antiviral therapy with oseltamivir 8
- Human metapneumovirus causes clinically indistinguishable bronchiolitis from RSV, occurs in similar age groups and seasons, but can be differentiated only by specific viral testing 8
- Bacterial pneumonia shows focal consolidation on chest radiograph, higher fever, elevated white blood cell count with left shift, and responds to antibiotic therapy 8
RSV bronchiolitis typically affects infants <2 years during winter months, presents with rhinorrhea, cough, wheezing, tachypnea, and respiratory distress, with diffuse crackles and wheezes on examination 8.
Scoliosis
The three key differential diagnoses for structural scoliosis are neuromuscular scoliosis, congenital vertebral anomalies, and spinal cord tumors.
- Neuromuscular scoliosis occurs in children with cerebral palsy, muscular dystrophy, or spinal muscular atrophy, shows progressive curves with pelvic obliquity, and requires evaluation of underlying neuromuscular condition 8
- Congenital vertebral anomalies (hemivertebrae, failure of segmentation) present in early childhood, show rigid curves that don't correct with bending, and require CT or MRI for detailed vertebral anatomy 8
- Spinal cord tumors manifest with rapidly progressive curves, neurologic deficits, back pain (uncommon in idiopathic scoliosis), and require urgent MRI of entire spine 8
Idiopathic scoliosis (most common) presents in adolescents (especially females), shows flexible curves that partially correct with forward bending, has no neurologic deficits, and demonstrates normal skin examination without midline abnormalities 8.
Febrile Seizures
The three key differential diagnoses for febrile seizures are meningitis/encephalitis, electrolyte disturbances, and epilepsy.
- Meningitis/encephalitis presents with fever plus altered mental status, meningismus, focal neurologic deficits, or prolonged postictal state, and requires lumbar puncture for CSF analysis 8
- Electrolyte disturbances (hyponatremia, hypoglycemia, hypocalcemia) show seizures with fever but have abnormal serum electrolytes, may have underlying metabolic disorder, and require specific electrolyte correction 8
- Epilepsy with concurrent febrile illness demonstrates seizures that are prolonged (>15 minutes), focal, or recurrent within 24 hours, may have abnormal neurologic examination, and requires EEG evaluation 8
Simple febrile seizures occur in children 6 months to 5 years with fever >38°C, are generalized tonic-clonic lasting <15 minutes, occur once in 24 hours, have rapid return to baseline mental status, and show normal neurologic examination 8.