What diseases and syndromes are characteristic of each pediatric age‑of‑onset group?

Pediatric Diseases and Syndromes by Age of Onset

To effectively reason through pediatric presentations, organize your differential diagnosis by recognizing that certain diseases cluster distinctly by age, with structural anomalies dominating infancy, metabolic and genetic syndromes emerging in early childhood, and autoimmune/inflammatory conditions becoming prominent in adolescence.

Neonatal Period (Birth to 28 Days)

Immediate Presentation (0-7 Days)

• Neonatal diabetes: Occurs under 6 months of age, with 80-85% having an underlying monogenic cause; most commonly due to KATP channel mutations (KCNJ11, ABCC8) or chromosome 6q24 abnormalities 1
• Severe Combined Immunodeficiency (SCID): Presents with failure to thrive, diarrhea, severe/disseminated infections, opportunistic infections, and rash; detectable on newborn screening 1
• DiGeorge Syndrome (22q11.2 deletion): Hypocalcemic seizures from hypoparathyroidism, cardiac disease, abnormal facies; detectable on newborn screening 1
• Congenital heart disease with genetic syndromes: Structural cardiac anomalies are primarily noted in infancy across multiple syndromes 1

First Month Complications

• Infantile-onset Pompe disease (IOPD): Apparent shortly after birth with hypotonia, muscle weakness, failure to thrive, and hypertrophic cardiomyopathy; death from respiratory failure often occurs in first 2 years if untreated 1
• Infantile neurovisceral acid sphingomyelinase deficiency (ASMD): Symptom onset in early infancy with rapidly progressive hepatosplenomegaly, pulmonary involvement, neurodegeneration, hypotonia, and failure to thrive; death typically before 3 years 1
• Krabbe disease (infantile-onset): Rapid neurodegeneration and early death in majority of patients 1

Infancy (1-12 Months)

Early Infancy (1-6 Months)

• Spinal muscular atrophy and neuromuscular disorders: Hypotonia and motor delays become apparent 1
• Infantile spasms and early epilepsy syndromes: Seizures with developmental regression 2
• Congenital alveolar dysplasia and surfactant dysfunction disorders: Respiratory distress requiring evaluation for childhood interstitial lung disease (chILD) syndrome 1

Late Infancy (6-12 Months)

• Developmental delay recognition: Psychomotor development plateaus between 6-15 months in severe neurodegenerative conditions 1
• Gaucher disease type 2: Acute neuronopathic form with hydrops fetalis, hepatosplenomegaly, anemia, thrombocytopenia, interstitial lung disease, seizures, bulbar palsy, hypertonia 1
• Immunodeficiency presentations: Recurrent serious infections become apparent; Wiskott-Aldrich syndrome presents with thrombocytopenia, bleeding, bruising, eczema, and recurrent infections 1

Early Childhood (1-5 Years)

Toddlers (1-3 Years)

• Behavioral disorders: Most common presentation in children <5 years in neurological clinics (16% overall prevalence) 2
• Cerebral palsy: 10.5% of pediatric neurological presentations, more prevalent in <5 years age group 2
• Chronic granulomatous disease (CGD): Deep-seated infections and abscesses with granuloma formation 1
• Leukocyte adhesion deficiency (LAD): Delayed umbilical cord separation, poor wound healing, lack of pus formation, recurrent serious bacterial infections 1

Preschool Age (3-5 Years)

• Type 1 diabetes: Three-quarters of all type 1 diabetes cases are diagnosed in individuals <18 years, with significant numbers in early childhood 1
• Chronic visceral ASMD: Hepatosplenomegaly in early childhood, though mild disease may not be diagnosed until adulthood 1
• Ataxia-telangiectasia: Chronic sinopulmonary disease, cerebellar ataxia, oculocutaneous telangiectasia, malignancy risk 1

School Age (6-12 Years)

Early School Age (6-9 Years)

• Epilepsy: Most common neurological disorder across all pediatric ages (36% prevalence), but continues to be diagnosed throughout childhood 2
• 22q11.2 deletion syndrome features: Developmental delay and cognitive deficits become particularly evident as educational demands increase 1
• Chronic neurovisceral ASMD: Ataxia, gross motor delays, and learning disabilities commonly seen 1

Late School Age (9-12 Years)

• MODY (Maturity-Onset Diabetes of the Young): Progressive insulin secretory defect with presentation in adolescence or early adulthood for HNF1A-MODY and HNF4A-MODY 1
• Hyper-IgE syndrome (HIES) type 1: Chronic dermatitis, recurrent serious lung infections with pneumatoceles, skin infections, bone fragility, failure to shed primary teeth 1
• Noonan syndrome manifestations: Mean IQ 84, with cardiac manifestations (pulmonary valve stenosis, ASD, hypertrophic cardiomyopathy) 1

Adolescence (13-18 Years)

Early Adolescence (13-15 Years)

• Still's disease (systemic JIA): Recurrent spiking fever, skin rash, arthralgia/arthritis, high inflammation markers; can present throughout childhood but becomes more evident with increasing environmental demands 1
• Multiple sclerosis: Pediatric MS starting before 12 years is less common; later-onset group (≥12 years) has higher female/male ratio, less frequent initial ADEM presentation, more frequent spinal cord involvement 3
• Inflammatory bowel disease: Part of autoimmune disease spectrum in 22q11.2DS and other genetic syndromes 1

Late Adolescence (15-18 Years)

• Psychiatric manifestations of 22q11.2DS: Behavioral differences become particularly evident in adolescence as individuals face increasing educational and social demands 1
• Late-onset Pompe disease (LOPD): Can present anytime from late infancy to adulthood with myopathy progressing to respiratory insufficiency; cardiac involvement rare 1
• Chest pain and respiratory symptoms: More frequent in older pediatric age groups (145-210 months) 4

Age-Specific Clinical Pearls

Infection Patterns by Age

• Viral co-infections: Most common in 0-6 year age group (31.6% in pediatrics); decrease with age in children but increase again in elderly adults 5
• Respiratory infections: Viral infection and co-infection rates decrease with age in pediatric patients 5

Trauma Patterns by Age

• Spinal cord injury without radiologic abnormalities (SCIWORA): Predominant in children <4 years; none observed in 13-18 year age group 6
• Spinal fractures: Account for >60% of SCI in 13-18 year age group, compared to congenital anomalies in younger children 6

Genetic Syndrome Recognition

• Down syndrome (Trisomy 21): 40% have congenital heart disease (AVSD, VSD, TOF, PDA); median IQ 50; requires hearing assessments every 6 months starting at birth 1
• Turner syndrome: 30% have cardiac anomalies (bicuspid aortic valve, coarctation of aorta); mean IQ 90 1
• Williams syndrome: 60% have supravalvar aortic stenosis or peripheral pulmonary stenosis; mean IQ 56 with visual-spatial impairments 1

High-Risk Cardiac Populations

• Neonates/infants requiring open heart surgery: At highest risk for developmental disorders regardless of cyanotic vs acyanotic lesions (HLHS, IAA, PA/IVS, TA, TAPVC, TGA, TOF, tricuspid atresia) 1
• Comorbidities increasing risk: Prematurity (<37 weeks), ECMO/VAD use, heart transplantation, cardiopulmonary resuscitation, prolonged hospitalization (>2 weeks), perioperative seizures, significant neuroimaging abnormalities 1