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Emergency and Acute Medicine – Lymphadenitis
Basics description
Lymphadenitis refers to inflammation and enlargement of lymph nodes, most commonly as part of a systemic response to infection. Nodes become engorged with lymphocytes and macrophages and may be secondarily involved from infection in a distal extremity, producing painful, tender adenopathy proximally. Acute suppurative lymphadenitis may follow pharyngeal or skin infections and can progress to abscess formation.
Etiology
Lymphadenitis is most frequently caused by bacterial infection. The most common organisms in pyogenic lymphadenitis are Staphylococcus aureus, including community-associated methicillin-resistant S. aureus (CA-MRSA), and group A β-hemolytic Streptococcus. CA-MRSA risk factors include prior MRSA infection, household exposure, military service, incarceration, contact sports, injection drug use, and men who have sex with men. Cervical lymphadenitis usually originates from pharyngeal or periodontal infections and commonly involves streptococci and anaerobes. Axillary lymphadenitis is often caused by group A streptococcus. Nosocomial MRSA should be suspected in patients with recent hospitalization, surgery, dialysis, vascular catheters, recent antibiotic use, or unresponsive infection. In children, acute unilateral cervical suppurative lymphadenitis is most common in those younger than six years and is typically caused by S. aureus, group A streptococcus, or anaerobes.
Diagnosis signs and symptoms
Patients typically present with painful swelling and inflammation of affected lymph nodes, often in association with cellulitis or abscess if the cause is pyogenic. Axillary lymphadenitis may present with fever, axillary pain, and acute lymphedema of the arm or chest and may be associated with ipsilateral pleural effusion. History should include duration of lymphadenopathy, pain, fever, night sweats, weight loss, fatigue, sore throat, cough, occupational and animal exposures, sexual history, drug use, and travel. Physical examination should assess whether lymphadenopathy is localized or generalized, node size, tenderness, overlying skin changes, presence of skin lesions, splenomegaly, and involvement of supraclavicular or scalene nodes, which is always abnormal.
Essential workup
Acute regional lymphadenitis is usually a clinical diagnosis and often part of a broader infectious syndrome such as cellulitis. History and physical examination should focus on identifying an infectious source.
Diagnosis tests and interpretation
Laboratory testing is not always required. A CBC may show leukocytosis with left shift or be normal. Serologic testing for EBV, CMV, HIV, or other pathogens should be guided by clinical suspicion. Ultrasound or CT imaging is indicated when patients fail to improve with therapy or when suppuration is suspected. Percutaneous needle aspiration or surgical drainage should be considered if abscess formation occurs or if there is poor clinical response.
Differential diagnosis
The differential diagnosis includes common infections such as adenovirus, scarlet fever, cat scratch disease, fungal infections, and herpes zoster, as well as unusual infections including sporotrichosis, diphtheria, plague, anthrax, typhoid, rubella, and West Nile virus. Sexually transmitted infections, systemic infections such as HIV, infectious mononucleosis, toxoplasmosis, tuberculosis, hepatitis, and dengue should be considered. Noninfectious causes include drug reactions, malignancy, rheumatologic disorders, and pediatric-specific conditions such as Kawasaki disease and PFAPA syndrome.
Treatment
Initial management includes ensuring airway, breathing, and circulation stability. Treatment is directed at the underlying cause and should account for local resistance patterns, including CA-MRSA prevalence. Outpatient therapy typically lasts 7–10 days and includes limb elevation, moist heat, analgesics, and antibiotics. Abscesses require drainage with culture when possible. Skin-source infections are commonly treated with oral cephalexin plus trimethoprim–sulfamethoxazole or alternatives such as clindamycin or doxycycline. Pharyngeal or periodontal sources are treated with penicillin VK or alternatives such as clindamycin or amoxicillin–clavulanate. Inpatient therapy may require IV penicillin-based regimens with MRSA coverage using vancomycin or clindamycin when indicated.
Disposition and follow-up
Admission is indicated for toxic-appearing patients, those with immunosuppression or significant comorbidities, inability to tolerate oral therapy, or unreliable follow-up. Patients with mild infection who are nontoxic, can take oral antibiotics, and have reliable follow-up within 24–48 hours may be discharged. Failure to resolve promptly with antibiotics should prompt evaluation for malignancy or other serious causes, and lymph node biopsy may be indicated for persistent, large, or supraclavicular nodes.
Pearls and pitfalls
Staphylococcus species are the most common cause of acute regional pyogenic lymphadenitis. Empiric antibiotic therapy should include coverage for CA-MRSA in addition to streptococci, particularly in unresponsive or high-risk infections.
Basics description
Lymphadenitis refers to inflammation and enlargement of lymph nodes, most commonly as part of a systemic response to infection. Nodes become engorged with lymphocytes and macrophages and may be secondarily involved from infection in a distal extremity, producing painful, tender adenopathy proximally. Acute suppurative lymphadenitis may follow pharyngeal or skin infections and can progress to abscess formation.
Etiology
Lymphadenitis is most frequently caused by bacterial infection. The most common organisms in pyogenic lymphadenitis are Staphylococcus aureus, including community-associated methicillin-resistant S. aureus (CA-MRSA), and group A β-hemolytic Streptococcus. CA-MRSA risk factors include prior MRSA infection, household exposure, military service, incarceration, contact sports, injection drug use, and men who have sex with men. Cervical lymphadenitis usually originates from pharyngeal or periodontal infections and commonly involves streptococci and anaerobes. Axillary lymphadenitis is often caused by group A streptococcus. Nosocomial MRSA should be suspected in patients with recent hospitalization, surgery, dialysis, vascular catheters, recent antibiotic use, or unresponsive infection. In children, acute unilateral cervical suppurative lymphadenitis is most common in those younger than six years and is typically caused by S. aureus, group A streptococcus, or anaerobes.
Diagnosis signs and symptoms
Patients typically present with painful swelling and inflammation of affected lymph nodes, often in association with cellulitis or abscess if the cause is pyogenic. Axillary lymphadenitis may present with fever, axillary pain, and acute lymphedema of the arm or chest and may be associated with ipsilateral pleural effusion. History should include duration of lymphadenopathy, pain, fever, night sweats, weight loss, fatigue, sore throat, cough, occupational and animal exposures, sexual history, drug use, and travel. Physical examination should assess whether lymphadenopathy is localized or generalized, node size, tenderness, overlying skin changes, presence of skin lesions, splenomegaly, and involvement of supraclavicular or scalene nodes, which is always abnormal.
Essential workup
Acute regional lymphadenitis is usually a clinical diagnosis and often part of a broader infectious syndrome such as cellulitis. History and physical examination should focus on identifying an infectious source.
Diagnosis tests and interpretation
Laboratory testing is not always required. A CBC may show leukocytosis with left shift or be normal. Serologic testing for EBV, CMV, HIV, or other pathogens should be guided by clinical suspicion. Ultrasound or CT imaging is indicated when patients fail to improve with therapy or when suppuration is suspected. Percutaneous needle aspiration or surgical drainage should be considered if abscess formation occurs or if there is poor clinical response.
Differential diagnosis
The differential diagnosis includes common infections such as adenovirus, scarlet fever, cat scratch disease, fungal infections, and herpes zoster, as well as unusual infections including sporotrichosis, diphtheria, plague, anthrax, typhoid, rubella, and West Nile virus. Sexually transmitted infections, systemic infections such as HIV, infectious mononucleosis, toxoplasmosis, tuberculosis, hepatitis, and dengue should be considered. Noninfectious causes include drug reactions, malignancy, rheumatologic disorders, and pediatric-specific conditions such as Kawasaki disease and PFAPA syndrome.
Treatment
Initial management includes ensuring airway, breathing, and circulation stability. Treatment is directed at the underlying cause and should account for local resistance patterns, including CA-MRSA prevalence. Outpatient therapy typically lasts 7–10 days and includes limb elevation, moist heat, analgesics, and antibiotics. Abscesses require drainage with culture when possible. Skin-source infections are commonly treated with oral cephalexin plus trimethoprim–sulfamethoxazole or alternatives such as clindamycin or doxycycline. Pharyngeal or periodontal sources are treated with penicillin VK or alternatives such as clindamycin or amoxicillin–clavulanate. Inpatient therapy may require IV penicillin-based regimens with MRSA coverage using vancomycin or clindamycin when indicated.
Disposition and follow-up
Admission is indicated for toxic-appearing patients, those with immunosuppression or significant comorbidities, inability to tolerate oral therapy, or unreliable follow-up. Patients with mild infection who are nontoxic, can take oral antibiotics, and have reliable follow-up within 24–48 hours may be discharged. Failure to resolve promptly with antibiotics should prompt evaluation for malignancy or other serious causes, and lymph node biopsy may be indicated for persistent, large, or supraclavicular nodes.
Pearls and pitfalls
Staphylococcus species are the most common cause of acute regional pyogenic lymphadenitis. Empiric antibiotic therapy should include coverage for CA-MRSA in addition to streptococci, particularly in unresponsive or high-risk infections.
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