Atypical Mycobacterial Infections The 5 Minute Pediatric Consult


	Atypical Mycobacterial Infections

Richard M. Rutstein

Database
Differential Diagnosis
Data Gathering
Physical Examination
Laboratory Aids
Therapy
Follow-Up
Common Questions and Answers
Bibliography

DATABASE

DEFINITION

Atypical mycobacterial (ATM) infection refers to disease caused by Mycobacterium other than tuberculosis, bovis, and leprae, and usually involves Mycobacterium avium-intracellularae or M. scrofulaceum. These diseases are also referred to as nontuberculous mycobacterial infections, environmental mycobacterial infections, and mycobacteria other than tuberculosis (MOTT) infections.

CAUSES

The most common associated illness is unilateral chronic cervical adenopathy/adenitis in preschool-aged children.
In adults, ATM infection may cause a chronic single pulmonary nodule or more extensive chronic lung disease.
In children and adults infected with HIV, disseminated disease is common, yet it is not common in other acquired or congenital immunodeficiencies that affect T-cell function.
Rarely, it may cause otitis/mastoiditis in immunocompetent children.
Chronic skin, bone, or soft-tissue infections may develop after trauma/surgery, usually with M. chelonei or M. fortuitum as the etiologic agents.

PATHOPHYSIOLOGY

Organisms are ubiquitous in the environment: soil, fresh water, ocean water, home and hospital water, dust, and food (eggs, dairy products, meat).
It is spread by aerosol inhalation or ingestion of contaminated food, dust, or water.
Person-to-person spread has never been documented and is not a concern.

EPIDEMIOLOGY

80% to 90% of cases of adenitis caused by ATM infection occur in preschool-aged children (ages 1–5 years).
Early in the HIV epidemic, the incidence rate of disseminated disease in HIV-infected adults was approximately 40%; in HIV-infected children, 10% to 20%. This rate has decreased markedly in recent years through the routine use of prophylaxis and because of the improved immunologic function in HIV-infected individuals on newer antiretroviral agents.

COMPLICATIONS

Chronic draining of infected cervical nodes
Rarely, pulmonary disease or dissemination
Chronic skin/bone infections
Disseminated disease

PROGNOSIS

For localized adenopathy: excellent
For disseminated disease, generally treatable in the rare immunocompetent individual
In patients with AIDS, treatable in terms of symptom relief, but requires lifelong therapy

DIFFERENTIAL DIAGNOSIS

For unilateral adenopathy/adenitis:
- Viral/bacterial adenitis-affected nodes are tender, warm, and erythematous; usually associated with upper respiratory symptoms and/or fever.
- Cat-scratch disease (contact with cat, usually kitten). Frequently, child will have scratch/puncture mark on arm. There are rarely any systemic signs/symptoms.
Neoplastic disease

DATA GATHERING

HISTORY

Region of residence
Recent travel
Length of time of adenopathy, associated systemic symptoms
Contact with cats (for differential of cat-scratch disease or toxoplasmosis)
Systemic symptoms, such as fever and weight loss, make neoplastic disease more likely.
Chronic cough would suggest M. tuberculosis.
Recent upper respiratory symptoms/fever suggest viral or bacterial cause.

PHYSICAL EXAMINATION

Most common: Single or regional cervical adenopathy, 90% of the time, is unilateral, firm, not fixed, and not especially tender nor warm; occasionally, there is spontaneous drainage.
Generalized adenopathy makes ATM disease unlikely.
Systemic signs of infection are absent.
Hepatosplenomegaly indicates other diagnosis, especially neoplastic disease or HIV-related illness.
Normal nutritional status

LABORATORY AIDS

Specific PPD tests are not readily available at this time. Many children with ATM adenitis will have 5- to 10-mm reactions to standard PPD.
Definitive diagnosis is made by isolation and identification of organism. The most frequently identified strains are: M. avium-intracellularae, M. kansasii, M. chelonei, M. fortuitum, and M. scrofulaceum.
Normal chest radiograph
In disseminated disease, cultures are positive from blood and bone marrow aspirates.

THERAPY

Complete surgical excision for isolated adenopathy secondary to ATM; chemotherapy unnecessary in most cases.
For disseminated or pulmonary disease, three- or four-drug treatment regimens based on sensitivity. Combinations generally include several of the following antibiotics: rifampin, isoniazid, rifabutin, clarithromycin or azithromycin, ethambutol, ciprofloxin, and amikacin.

PREVENTION

For HIV-infected children with severe immunodeficiency, prophylaxis with daily clarithromycin or rifabutin, or once-weekly azithromycin, decreases the risk of development of disseminated disease.

FOLLOW-UP

Routine follow-up should be done for 1 year after excision to monitor for possible local/contralateral recurrence.

PITFALLS

Use of incision and drainage/aspiration for treatment of adenitis, which can lead to chronically draining node. Aspiration may be needed to make the original diagnosis, but total excision results in almost 100% cure rates.

COMMON QUESTIONS AND ANSWERS

Q: Should all cases of cervical adenitis be tested for ATM?
A: The typical case of cervical adenitis, presenting with the usual prodrome, responds rapidly to appropriate oral or parenteral antibiotics, which would not be the case if ATM were the culprit. Certainly, a PPD test should be done on all children with cervical adenitis. If the node is aspirated, in addition to routine bacterial cultures, fluid should be sent for mycobacterial culture.

Q: Should patients with disease secondary to ATM undergo a chest x-ray study?
A: Yes. Though uncommon, ATM-related pulmonary disease can be seen in children.

Q: If the node is excised, should oral therapy be instituted?
A: Most studies suggest that oral therapy is unnecessary following total excision.

ICD-9-CM 031.9

BIBLIOGRAPHY

Saitz EW. Cervical lymphadenitis caused by atypical mycobacteria. Pediatr Clin North Am 1981;28:823–839.

Smith MHD, Starke JR, Marquis JR. Tuberculosis and opportunistic mycobacterial infections. In: Feigin R, Cherry J, eds. Pediatric infectious diseases, 3rd ed. Philadelphia: WB Saunders, 1992:1354–1356.

Schaad UB, Votteler TP, McCracken GH, Nelson JD. Management of atypical mycobacterial lymphadenitis in childhood: a review based on 380 cases. J Pediatr 1979;95:356–360.

Taha AM, Davidson PT, Bailey WC. Surgical treatment of atypical mycobacterial lymphadenitis in children. Pediatr Infect Dis J 1985;4:664–667.

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