Overview
Definition:
Atypical mycobacterial lymphadenitis, also known as nontuberculous mycobacterial (NTM) lymphadenitis, refers to a chronic granulomatous infection of the lymph nodes caused by mycobacteria other than Mycobacterium tuberculosis complex
In toddlers, it commonly presents as unilateral cervical lymphadenopathy.
Epidemiology:
It is the most common form of NTM disease in immunocompetent children, with an incidence that varies geographically
Toddlers (ages 1-3 years) are particularly susceptible due to their developing immune systems and increased exposure to environmental sources like soil and water.
Clinical Significance:
While generally self-limiting, it can mimic other serious conditions, leading to unnecessary investigations and treatments
Understanding its unique presentation and management is crucial for accurate diagnosis, appropriate antibiotic selection, and avoiding surgical interventions when not indicated, thereby impacting patient outcomes and healthcare resource utilization.
Clinical Presentation
Symptoms:
Painless, gradually enlarging unilateral cervical lymphadenopathy
Absence of systemic symptoms like fever or weight loss is typical
Some children may develop a persistent cough or nasal discharge if there is associated pulmonary or sinonasal involvement, but this is less common in toddlers.
Signs:
A firm, nontender, mobile to fixed enlarged lymph node in the neck, most commonly in the anterior or posterior cervical chains
The overlying skin may become erythematous, thinned, and can eventually form a draining sinus tract, though this is a later manifestation
No significant constitutional symptoms are usually present.
Diagnostic Criteria:
Diagnosis is typically suspected based on characteristic clinical presentation and confirmed by microbiological and histological findings
While no formal "criteria" exist in the same sense as for some acute infections, a strong clinical suspicion in the absence of typical bacterial causes, coupled with positive cultures or pathology, establishes the diagnosis.
Diagnostic Approach
History Taking:
Detailed history should focus on the onset and duration of lymphadenopathy, presence of pain, associated systemic symptoms (fever, weight loss, cough), recent travel or exposure to soil/water, and prior infections or immune deficiencies
Ask about contact with individuals with tuberculosis.
Physical Examination:
Thorough examination of the head and neck for enlarged lymph nodes
Palpate all lymph node chains, noting size, consistency, tenderness, mobility, and presence of overlying skin changes
Assess for pharyngeal or tonsillar lesions
Perform a complete physical examination to rule out other causes of lymphadenopathy and systemic involvement.
Investigations:
Complete Blood Count (CBC) with differential may show mild lymphocytosis or normal values
Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP) are often normal or only mildly elevated
Fine Needle Aspiration (FNA) or biopsy of the enlarged lymph node is essential for definitive diagnosis: Gram stain, acid-fast bacilli (AFB) smear and culture, and histopathology (granulomatous inflammation)
Polymerase Chain Reaction (PCR) for mycobacteria can provide rapid identification.
Differential Diagnosis:
Bacterial lymphadenitis (Staphylococcus aureus, Streptococcus pyogenes), reactive lymphadenopathy due to viral infections, Kawasaki disease, Cat-scratch disease, tuberculosis, malignancy (lymphoma), and other atypical mycobacterial infections (e.g., Mycobacterium marinum if history of aquatic exposure).
Management
Initial Management:
Observation for small, asymptomatic nodes, especially in younger toddlers, as spontaneous resolution can occur
If there is suspicion of bacterial infection, a short course of empirical antibiotics may be initiated while awaiting investigations, but this is often ineffective against NTM.
Medical Management:
Antimycobacterial therapy is indicated for symptomatic, rapidly growing, or large nodes, or those with draining sinuses
Regimens typically involve multiple drugs for at least 6-12 months
Common regimens include clarithromycin or azithromycin plus ethambutol and/or rifampicin
Specific drug choices depend on the identified NTM species and local resistance patterns
Combination therapy is crucial to prevent resistance.
Surgical Management:
Surgical excision of involved lymph nodes is generally not the primary treatment and is reserved for cases with extensive disease, treatment failure, or significant cosmetic deformity after medical management
In cases where a sinus tract has formed, debulking or removal of the affected node may be considered in conjunction with medical therapy.
Supportive Care:
Reassurance for parents regarding the benign nature of the condition and the long treatment duration
Adequate hydration and nutrition
Close monitoring for treatment adherence and potential side effects of medications, such as rash, gastrointestinal upset, or visual changes (with ethambutol).
Complications
Early Complications:
Formation of draining sinuses with secondary bacterial infection
Persistent lymphadenopathy despite treatment
Local tissue damage and scarring.
Late Complications:
Cosmetic disfigurement from scarring and sinus tracts
Recurrence of infection if treatment is incomplete or non-adherent
Spread to other sites, though rare in immunocompetent children.
Prevention Strategies:
Primary prevention is difficult as NTM are ubiquitous in the environment
Focus on prompt diagnosis and appropriate, complete multi-drug therapy to minimize disease progression and complications
Educating parents on the importance of adherence to the long treatment course is vital.
Prognosis
Factors Affecting Prognosis:
The main prognostic factors are the specific species of NTM, the extent of lymph node involvement, and adherence to a prolonged, multi-drug treatment regimen
Early diagnosis and treatment generally lead to a good prognosis.
Outcomes:
With appropriate therapy, most children achieve clinical cure and resolution of lymphadenopathy
However, residual scarring or cosmetic changes can occur
The duration of treatment is typically 6-12 months, and follow-up is important to ensure cure.
Follow Up:
Follow-up is essential for at least 6 months after completion of therapy to monitor for recurrence or complications
Regular clinical assessments are performed
In cases of treatment failure or significant side effects, adjustments to the regimen are made based on drug susceptibility testing.
Key Points
Exam Focus:
Remember that atypical mycobacterial lymphadenitis is the MOST COMMON mycobacterial infection in immunocompetent children, often presenting as PAINLESS cervical lymphadenopathy
Diagnosis requires microbiological confirmation (AFB smear, culture, PCR) and histopathology
Treatment is PROLONGED (6-12 months) with MULTIDRUG therapy.
Clinical Pearls:
Consider NTM lymphadenitis in any toddler with chronic, unilateral cervical lymphadenopathy that is not responding to empirical antibiotics
FNA is diagnostic and therapeutic
it can sometimes lead to resolution without further treatment
Avoid surgical excision as a primary modality unless medical management fails or complications like sinus tracts arise.
Common Mistakes:
Mistaking NTM lymphadenitis for bacterial cervical lymphadenitis and treating with short courses of antibiotics
Delaying diagnosis due to assuming it is reactive lymphadenopathy
Inadequate treatment duration or regimen, leading to treatment failure or resistance
Undertreating by relying solely on FNA without appropriate medical therapy for confirmed cases.