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Infectious Diseases
Mycobacterial infections: TB screening, diagnosis, and treatment in children
Clinical Overview and When to Suspect Tuberculosis in Children
Mycobacterium tuberculosis (MTB) is an acid-fast bacillus transmitted via respiratory droplets. Children are usually infected by a close adult contact with active pulmonary TB.
Pediatric TB exists on a spectrum: TB exposure → latent TB infection (LTBI) → active TB disease
LTBI: positive screening test, no symptoms, normal CXR → child is infected but NOT infectious
Active TB disease: symptoms ± abnormal imaging ± positive cultures → may be infectious (rarely in children <10 yr due to paucibacillary disease and poor cough force)
Suspect TB when: child has prolonged unexplained fever, persistent non-remitting cough >2–3 weeks, failure to thrive, unexplained lymphadenopathy, or known close contact with active TB
High-risk populations: foreign-born children (or parents) from endemic areas, household contacts of active TB cases, children in homeless shelters/correctional facilities, HIV-infected children, immunosuppressed patients
Board pearl: Young children (<5 years) are at highest risk for rapid progression from LTBI → active disease (including disseminated/miliary TB and TB meningitis) — this is WHY we screen aggressively and treat LTBI in this age group
Nontuberculous mycobacteria (NTM) — especially M. avium complex — cause cervical lymphadenitis in immunocompetent toddlers and should be distinguished from MTB
History — Exposure Assessment and Risk Stratification
The history in pediatric TB centers on epidemiologic risk and contact tracing:
Identify the source case: any household member or close contact with active TB, chronic cough, hemoptysis, weight loss, recent incarceration, homelessness, immigration from endemic country?
Travel history: prolonged stay (>1 week) in TB-endemic regions (Southeast Asia, Sub-Saharan Africa, Central America, India, China)
HIV status of the child and family members — HIV dramatically ↑ risk of progression
Immunosuppressive medications: TNF-α inhibitors, high-dose corticosteroids, post-transplant regimens
BCG vaccination history: commonly given at birth in endemic countries — affects TST interpretation (not IGRA)
Symptom timeline: active pulmonary TB in children → persistent non-remitting cough, fever, night sweats, weight loss/poor weight gain, fatigue over weeks to months
Clinical tip: Children <5 years are often asymptomatic at diagnosis — disease is found through contact investigation, NOT because the child presented with symptoms
Ask about prior TB testing results and any history of TB treatment or prophylaxis
Physical Exam — Active TB Disease Patterns
Pulmonary TB (most common pediatric form):
Extrapulmonary TB — more common in young children than adults:
Exam may be surprisingly normal despite significant CXR findings
Persistent cough, tachypnea, focal crackles/decreased breath sounds; rarely hemoptysis in young children
TB lymphadenitis: firm, non-tender, matted cervical/supraclavicular nodes; may develop sinus tracts
TB meningitis: gradual onset irritability, headache, vomiting, altered consciousness, cranial nerve palsies (especially CN VI), nuchal rigidity; basilar meningitis pattern
Miliary TB: disseminated disease → hepatosplenomegaly, diffuse lymphadenopathy, choroidal tubercles on fundoscopy, respiratory distress
Skeletal TB (Pott disease): vertebral gibbus deformity, focal back pain, paraplegia
Abdominal TB: ascites, abdominal mass, intestinal obstruction
Board pearl: In a toddler (1–4 yr) with a unilateral non-tender cervical mass, firm and slightly fluctuant → consider NTM lymphadenitis (M. avium complex) over MTB; NTM typically has no systemic symptoms and normal CXR; MTB lymphadenitis more likely with TB exposure/risk factors
Scrofula (TB cervical lymphadenitis) classically involves posterior cervical/supraclavicular nodes; NTM favors preauricular/submandibular nodes
Screening — Who, When, and How
Universal TB screening is NOT recommended. Targeted risk-based screening is the standard.
— Tuberculin skin test (TST/Mantoux): intradermal injection of 5 TU purified protein derivative (PPD), read at 48–72 hours; measures induration (NOT erythema)
— Interferon-gamma release assay (IGRA): blood test measuring T-cell IFN-γ response to MTB-specific antigens (ESAT-6, CFP-10); available as QuantiFERON-Gold or T-SPOT
AAP recommends using a risk-assessment questionnaire at well-child visits to identify children who need testing
Test WITH a risk factor present: born in/traveled to endemic country, contact with active TB case, contact with person who is incarcerated/homeless/uses IV drugs, HIV-positive child, child on immunosuppressive therapy
Two accepted screening tests:
Board pearl: IGRA is preferred in children ≥2 years who received BCG vaccine — IGRA is NOT affected by prior BCG. TST can be falsely positive after BCG vaccination
For children <2 years: TST is preferred (IGRA performance less well-studied); IGRA can be used as confirmatory
Either TST or IGRA (not both routinely) is acceptable for initial screening in children ≥2 years
Diagnostic Workup — Interpreting TST, IGRA, and Confirming Active Disease
TST interpretation — induration cutoffs depend on risk:
IGRA: Positive/negative/indeterminate; not affected by BCG or most NTM
Active disease workup (after positive screen):
≥5 mm: close contacts of active TB, HIV-positive, immunosuppressed, CXR consistent with prior TB
≥10 mm: children <5 years, children born in/traveled to endemic areas, children exposed to high-risk adults
≥15 mm: children ≥4 years with no risk factors (should not have been tested — reflects low-risk screening)
False-negative TST: anergy from severe TB, HIV, measles, malnutrition, young age (<6 months), recent live vaccines (MMR/varicella can suppress TST for 4–6 weeks → place TST same day as or ≥4 weeks after live vaccine)
CXR (AP + lateral): classic pediatric findings → hilar/mediastinal lymphadenopathy ± parenchymal infiltrate; Ghon focus (primary parenchymal lesion) + Ranke complex (calcified Ghon + calcified node)
Obtain 3 early-morning gastric aspirates (before child eats/moves) for AFB smear and culture — children rarely produce sputum; induced sputum in older children/adolescents
Mycobacterial culture (liquid media) is gold standard but takes 2–6 weeks; nucleic acid amplification tests (NAAT/GeneXpert) provide rapid species confirmation + rifampin resistance detection
Board pearl: Negative cultures do NOT rule out active TB in children — pediatric TB is paucibacillary; clinical/radiographic diagnosis with known exposure is often sufficient to initiate treatment
Management — Latent TB Infection (LTBI)
Treating LTBI prevents progression to active disease — critical in children <5 years where progression risk is highest (up to 40% in infants).
Preferred LTBI regimens:
— Dose: 10–15 mg/kg/day (max 300 mg)
— Supplement with pyridoxine (vitamin B₆) in exclusively breastfed infants, malnourished children, HIV-positive, or adolescents (prevents peripheral neuropathy)
— Dose: 15–20 mg/kg/day (max 600 mg)
Before starting LTBI treatment:
Isoniazid (INH) daily × 9 months — traditional standard; given as monotherapy
Rifampin daily × 4 months — alternative; preferred when INH resistance suspected or INH intolerance
INH + rifapentine weekly × 12 doses (3 months) — directly observed therapy; approved for children ≥2 years
MUST rule out active disease (symptoms + CXR ± gastric aspirates if any concern)
Baseline hepatic transaminases if underlying liver disease; routine LFT monitoring not required in healthy children but obtain if symptoms develop (nausea, vomiting, jaundice, dark urine)
Board pearl: INH hepatotoxicity is much rarer in children than adults — do NOT withhold treatment due to fear of hepatotoxicity in a child with LTBI
Management — Active TB Disease
Active TB in children requires multi-drug therapy to prevent resistance emergence.
Standard regimen for drug-susceptible pulmonary TB:
Dosing (pediatric-specific — higher mg/kg than adults):
Intensive phase (2 months): INH + rifampin + pyrazinamide + ethambutol (4-drug)
Continuation phase (4 months): INH + rifampin
Total duration: 6 months for uncomplicated pulmonary TB
INH: 10–15 mg/kg/day (max 300 mg)
Rifampin: 15–20 mg/kg/day (max 600 mg)
Pyrazinamide: 30–40 mg/kg/day (max 2 g)
Ethambutol: 20 mg/kg/day (max 1 g)
Ethambutol causes optic neuritis (↓ red-green color discrimination, ↓ visual acuity) — monitor vision; historically avoided in young children who cannot report visual changes, but AAP now supports use when 4th drug is needed
Pyrazinamide → hepatotoxicity, hyperuricemia
Rifampin → orange discoloration of secretions, hepatotoxicity, drug interactions (↑ CYP450 metabolism → ↓ levels of many drugs including OCPs, antiretrovirals)
Board pearl: When source case has known drug-susceptible TB, ethambutol can be dropped and 3-drug intensive phase (INH + RIF + PZA) used
Management — Special Situations and When to Refer
TB meningitis:
Drug-resistant TB:
HIV co-infection:
When to refer:
4-drug intensive phase × 2 months → INH + rifampin continuation × 7–10 months (total 9–12 months)
Add dexamethasone for TB meningitis — reduces mortality and neurologic sequelae
Ethambutol has poor CNS penetration → substitute ethionamide or an aminoglycoside in some protocols
MDR-TB (resistant to INH + rifampin) → requires 4–6 drug regimen guided by susceptibilities; refer to TB specialist/public health
GeneXpert/NAAT from gastric aspirate provides rapid rifampin resistance detection
Drug interactions between rifamycins and antiretrovirals (especially protease inhibitors) are complex → infectious disease/HIV specialist involvement mandatory
IRIS (immune reconstitution inflammatory syndrome) may occur when ART is initiated
All confirmed/suspected active TB → report to public health for contact investigation
MDR-TB, extrapulmonary TB, HIV co-infection, treatment failure, adverse drug reactions
Clinical tip: Directly observed therapy (DOT) is recommended for ALL active TB cases to ensure adherence and is coordinated through public health departments
Age-Specific Considerations — Neonates and Infants
Congenital TB: rare; acquired via hematogenous spread through umbilical vein (hepatic primary focus) or aspiration of infected amniotic fluid; presents in first weeks of life with hepatosplenomegaly, respiratory distress, fever, poor feeding
Perinatal exposure: infant born to mother with active TB → evaluate infant with CXR, TST/IGRA, gastric aspirates → if workup negative and infant asymptomatic → start INH (window prophylaxis) and separate from mother until she is on effective therapy and non-infectious; retest at 3–4 months
Infants <12 months with LTBI: highest risk age group for progression → ALWAYS treat
INH is first-line for LTBI in infants; supplement with pyridoxine in breastfed infants
TST preferred over IGRA for screening in children <2 years
BCG vaccine: given at birth in many countries; provides partial protection against disseminated/miliary TB and TB meningitis in young children; does NOT reliably prevent pulmonary TB; NOT routinely given in the U.S.
Board pearl: A positive TST in a BCG-vaccinated child should still be evaluated — BCG effect on TST wanes over 3–5 years and rarely causes induration ≥15 mm; IGRA can help clarify
Age-Specific Considerations — School-Age Children and Adolescents
School-age children (5–10 years) — relatively lower risk of progression from LTBI compared to infants and adolescents ('favored age'); still treat LTBI per guidelines
Adolescents: reactivation TB pattern emerges — upper lobe cavitary disease similar to adults; may be sputum smear-positive and infectious
Adolescents can produce sputum → induced sputum or spontaneous sputum preferred over gastric aspirates
Higher yield of AFB smear positivity in adolescents than young children
Screen adolescents with risk factors: recent immigration, incarceration, homelessness, substance use, HIV
IGRA is preferred in adolescents (especially BCG-vaccinated) — single blood draw, no return visit needed, objective result
Medication adherence is a major challenge in adolescents → DOT strongly recommended
Board pearl: Adolescents with cavitary pulmonary TB should be considered infectious and require airborne isolation (negative pressure room, N95 respirator for HCWs) — unlike young children who are rarely infectious
Rifampin interaction with oral contraceptives → counsel adolescent females about need for alternative contraception
Complications and When to Escalate Care
Complications of active TB in children:
When to hospitalize:
Miliary/disseminated TB: highest risk in infants and immunocompromised; diffuse miliary pattern on CXR (millet-seed nodules); multiorgan involvement → liver, spleen, bone marrow, meninges, choroid
TB meningitis: most devastating complication; presents subacutely with personality changes → meningismus → cranial nerve palsies → coma; CSF shows lymphocytic pleocytosis, ↑ protein, ↓↓ glucose (glucose often <30 mg/dL); basilar exudates on MRI → hydrocephalus
Airway compression: massive hilar/mediastinal lymphadenopathy can compress bronchi → lobar atelectasis, air trapping, or bronchiectasis
Pleural effusion: exudative, lymphocyte-predominant; pleural ADA (adenosine deaminase) ↑ is supportive
Suspected TB meningitis or miliary TB
Respiratory compromise from airway compression
Failure to thrive/inability to tolerate oral medications
Suspected MDR-TB pending susceptibilities
Board pearl: TB meningitis has a classic CSF profile — lymphocytic pleocytosis, very high protein, very low glucose — similar to fungal meningitis; distinguish from bacterial (PMN predominant) and viral (lymphocytic but normal glucose)
Drug Adverse Effects and Monitoring
Isoniazid (INH):
Rifampin:
Pyrazinamide:
Ethambutol:
Hepatotoxicity: ↑ transaminases; clinical hepatitis rare in children; monitor symptoms (nausea, vomiting, jaundice, dark urine) — obtain LFTs if symptomatic
Peripheral neuropathy: due to pyridoxine (B₆) depletion → supplement in breastfed infants, malnourished, HIV+, pregnant adolescents
Rare: drug-induced lupus, seizures (in overdose)
Orange discoloration of urine, tears, sweat (warn families — can stain contact lenses)
Hepatotoxicity, thrombocytopenia
Potent CYP450 inducer → ↓ levels of warfarin, OCPs, antiretrovirals, antiepileptics
Hepatotoxicity (most hepatotoxic of the first-line agents)
Hyperuricemia (usually asymptomatic; gout rare in children)
Arthralgias
Optic neuritis: dose-dependent; ↓ visual acuity, ↓ red-green color discrimination
Obtain baseline visual acuity; monthly monitoring if possible
Board pearl: If a child on TB therapy develops jaundice → STOP all hepatotoxic drugs (INH, RIF, PZA), check LFTs, and reintroduce one at a time after normalization; consult TB specialist
Key Differentials — Pulmonary Findings
When a child presents with chronic cough, hilar lymphadenopathy, or persistent infiltrate:
TB vs community-acquired pneumonia: Bacterial pneumonia is acute onset, responds to standard antibiotics; TB is indolent, progressive, non-responsive to standard antibiotics
TB vs fungal infection: Histoplasmosis and coccidioidomycosis can mimic TB (hilar LAD, granulomas, pulmonary nodules); geographic exposure is key (Ohio/Mississippi River valley for histo; Southwest US for cocci)
TB vs sarcoidosis: Bilateral hilar LAD, non-caseating granulomas; older children/adolescents; ↑ ACE level; no organisms on culture
TB vs lymphoma: Mediastinal lymphadenopathy in older child/adolescent; constitutional symptoms overlap; imaging and biopsy distinguish
TB vs foreign body aspiration: Persistent focal infiltrate or atelectasis in toddler; acute choking history; no systemic symptoms
Board pearl: A child with persistent pneumonia unresponsive to 2+ courses of appropriate antibiotics → consider TB, fungal infection, foreign body, or anatomic abnormality (sequestration, congenital cystic lesion)
Key Differentials — Lymphadenitis (MTB vs NTM)
Cervical lymphadenitis is a common board topic distinguishing MTB from nontuberculous mycobacteria (NTM):
— Age: typically 1–5 years, immunocompetent
— Unilateral, preauricular or submandibular nodes; firm, non-tender; may develop violaceous discoloration and sinus tracts
— Normal CXR, no systemic symptoms, no TB exposure
— TST may be weakly positive (5–14 mm) due to cross-reactivity; IGRA typically negative (MTB-specific)
— Treatment: complete surgical excision is curative; observation if surgery risky; macrolide ± ethambutol if surgery declined; incision & drainage worsens outcome (chronic fistula)
— Posterior cervical/supraclavicular nodes; matted
— Systemic symptoms, known TB contact/risk factors, abnormal CXR possible
— Strongly positive TST and/or IGRA
— Treatment: standard 4-drug anti-TB regimen
NTM lymphadenitis (M. avium complex most common):
MTB lymphadenitis (scrofula):
Board pearl: Excisional biopsy showing granulomatous inflammation with negative AFB cultures in a well-appearing toddler with unilateral submandibular mass → think NTM; IGRA negative supports NTM over MTB
I&D (incision and drainage) is contraindicated for NTM lymphadenitis — leads to chronic sinus tract
Preventive Care — Contact Investigation and Window Prophylaxis
Contact investigation is the cornerstone of pediatric TB prevention:
— If repeat test positive → CXR → complete LTBI treatment (9 months INH total)
— If repeat test negative and exposure has ended → can discontinue INH
When an adult is diagnosed with active TB → all household contacts (especially children <5 yr) must be evaluated with TST or IGRA + CXR
If initial TST/IGRA is negative in an exposed child <5 years → start 'window prophylaxis' with INH immediately (child may be in incubation period; TST/IGRA takes 2–12 weeks to convert)
Retest at 8–10 weeks after last exposure:
Children ≥5 years with negative initial test: some experts defer prophylaxis and retest at 8–10 weeks; judgment depends on intensity of exposure
Board pearl: Window prophylaxis is given to young children (<5 yr) with NEGATIVE initial TST who are exposed to active TB — do NOT wait for a positive test before starting; the risk of rapid progression in this age group is too high
All active TB cases must be reported to public health for contact investigation
Screening Schedules, BCG, and Anticipatory Guidance
— Live attenuated vaccine from M. bovis strain
— Given at birth in many TB-endemic countries
— Protects against disseminated TB and TB meningitis in young children (50–80% efficacy); less effective for pulmonary TB
— NOT routinely administered in the U.S.
— Prior BCG does NOT reliably explain a positive TST — a positive TST in a BCG-vaccinated child with risk factors should be evaluated as true positive
— IGRA is NOT affected by BCG → preferred test in BCG-vaccinated children ≥2 years
Universal TST screening at well-child visits is NOT recommended — use targeted risk-based screening with a validated questionnaire
Screen at any age if risk factor identified; no fixed screening ages recommended by AAP for low-risk children
BCG vaccine:
Anticipatory guidance: families from endemic countries should be counseled about TB risk during return travel visits; screen children after prolonged travel (>1 week)
Clinical tip: If a family asks about BCG scar and positive TST → explain that BCG effect on TST wanes over time, and the child's risk factors determine clinical significance; use IGRA to clarify
Family Counseling, Psychosocial Considerations, and Education
TB carries significant stigma in many communities → approach diagnosis with cultural sensitivity
Reassure families: LTBI is NOT contagious; child with LTBI can attend school/daycare without restriction
Active TB: child can return to school after initiation of effective therapy (minimum 2 weeks) AND clinical improvement; young children (<10 yr) are generally considered non-infectious
Explain duration of therapy (6–9 months for active disease; 4–9 months for LTBI) → emphasize completing full course to prevent relapse and resistance
DOT may be perceived as burdensome → coordinate with public health for home-based or school-based DOT
Medication side effects education: orange body fluids (rifampin), report jaundice or persistent vomiting immediately
Household contacts MUST be evaluated — source case is almost always an adult; finding and treating the source protects the child and community
Board pearl: If a young child is diagnosed with active TB → the next step is to identify the adult source case — the child did not infect themselves; this is a PUBLIC HEALTH imperative
Immigration-related concerns: reassure that TB evaluation and treatment do not affect immigration status in most circumstances; involve social work as needed
High-Yield Associations and Rapid-Fire Facts
LTBI: positive test + no symptoms + normal CXR → treat with INH × 9 months (or RIF × 4 months, or INH + rifapentine × 3 months)
TST: ≥5 mm positive in immunocompromised/close contacts; ≥10 mm in children <5 yr and high-risk groups; ≥15 mm in low-risk (who ideally shouldn't be tested)
IGRA preferred over TST in BCG-vaccinated children ≥2 years
Gastric aspirates × 3 early morning = standard specimen for culture in young children
GeneXpert MTB/RIF → rapid detection of MTB + rifampin resistance
Active pulmonary TB: 4-drug × 2 months → 2-drug × 4 months = 6 months total
TB meningitis: extend treatment to 9–12 months + adjunctive dexamethasone
NTM lymphadenitis: excision (NOT I&D); IGRA negative
Children <5 years + TB exposure + negative TST → window prophylaxis with INH
Congenital TB: hepatic primary focus; presents in first weeks of life
INH → hepatotoxicity, peripheral neuropathy (give B₆); rifampin → CYP inducer, orange secretions; PZA → hepatotoxicity, hyperuricemia; EMB → optic neuritis
Board pearl: GAS has never developed penicillin resistance; MTB has never developed pyrazinamide resistance from monotherapy — wait, actually PZA resistance DOES occur. The stewardship principle: NEVER treat active TB with monotherapy → resistance emerges rapidly
One-Line Recap
Pediatric TB management requires targeted risk-based screening (TST for <2 yr, IGRA preferred for BCG-vaccinated children ≥2 yr; interpret TST by risk-stratified induration cutoffs of ≥5/≥10/≥15 mm), aggressive treatment of LTBI especially in children <5 yr (INH × 9 months or rifampin × 4 months) including window prophylaxis for exposed young children with initially negative tests, multi-drug therapy for active disease (INH + RIF + PZA + EMB × 2 months → INH + RIF × 4 months; extend to 9–12 months + dexamethasone for TB meningitis), recognition that children are usually paucibacillary and non-infectious (gastric aspirates for culture; negative cultures do not exclude diagnosis), distinguishing NTM lymphadenitis from MTB (excision NOT I&D for NTM; IGRA helps differentiate), mandatory public health reporting with contact investigation to identify the adult source case, and monitoring for drug toxicities (INH → hepatotoxicity/neuropathy with B₆ supplementation; rifampin → CYP induction/orange secretions; PZA → hepatotoxicity; EMB → optic neuritis).
Board Question Stem Patterns
3-year-old immigrant child, asymptomatic, TST 12 mm, normal CXR → LTBI → INH × 9 months
18-month-old, household contact with active TB, TST 0 mm → window prophylaxis: start INH now, retest TST at 8–10 weeks
4-year-old with persistent cough × 6 weeks, weight loss, CXR shows hilar LAD → suspect TB → obtain gastric aspirates × 3, start 4-drug regimen
2-year-old BCG-vaccinated, TST 13 mm → next step: IGRA to help clarify (or treat as LTBI if risk factors present — do NOT dismiss as BCG effect)
6-year-old on INH develops jaundice → stop INH, check LFTs → hepatotoxicity
2-year-old with non-tender unilateral submandibular mass, normal CXR, TST 8 mm, IGRA negative → NTM lymphadenitis → excisional biopsy (NOT I&D)
Infant born to mother with active pulmonary TB → separate, evaluate infant (CXR, TST, gastric aspirates), start INH window prophylaxis if workup negative
Adolescent with upper lobe cavity, productive cough, weight loss, positive AFB smear → active TB, infectious → airborne isolation + 4-drug regimen + public health notification
Child on TB treatment asks about school return → can return after 2 weeks of effective therapy + clinical improvement
Child with TB meningitis → CSF: lymphocytic pleocytosis, ↑↑ protein, ↓↓ glucose → 4-drug regimen + dexamethasone × 9–12 months total
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