Non-tuberculous mycobacteria (NTM) have become an
increasingly important disease of childhood.
59 — 92% of mycobacterial cervicofacial infections in
children are a result of NTM. Mainly affects
children <5 years, with most occurring 16 — 36 months of
age. The great majority of children with
NTM are not immunologically impaired. The specific organisms
are M. avium—intracellulare (aka
MAC, 70% to 90% of cases), M. kansasii, M. scrofulaceum, M.
fortuitum, M. haemophilum, M.
abscessus, M. malmoense. Infection by M. bovis has decreased
dramatically with the institution of
milk pasteurization.
These organisms are commonly found in soil, water, dust,
aerosols, domestic and wild animals, milk,
and other food items. The portal of entry is believed to be
through the mouth, and the tonsils have
been implicated in particular. The predilection for younger
children is probably related to their
tendency to put contaminated objects in their mouths. The
tendency to present in the winter
months may reflect the greater likelihood of viral upper
respiratory infection in this season, which
might allow the causal organism easier access via inflamed
mucous membranes. When within the
macrophage, MAC is able to survive within a vacuole and may
ultimately use the macrophage as a
launching pad for infection if the host’s defences weaken.
The typical clinical presentation is of a painless, firm,
enlarging and persistent neck mass that has
failed to respond to antibiotic therapy in a paediatric
patient. The most common site of
mycobacterial infection in the neck is the anterior superior
cervical region, followed by the posterior
cervical, middle cervical, supraclavicular, and submental
regions. Atypical mycobacterial infection is
not infrequently found in the pre-auricular region. It tends
to occur unilaterally. The skin becomes
adherent to the surrounding tissues and develops a
characteristic violaceous discoloration. The
infection might progress to fluctuation and the development
of a draining sinus. These lesions
generally produce few systemic symptoms. The differential
diagnosis should include all diseases
specific to the salivary glands, tuberculous adenitis,
infectious mononucleosis, cat-scratch disease,
brucellosis, actinomycosis, nocardiosis, toxoplasmosis,
malignancies (especially lymphoma), and
macrocystic lymphatic malformation.
In addition cervical lymphadenitis, NTM may be involved with
chronic otitis media (M. avium, M.
fortuitum, M. abscessus), or chronic laryngitis (M. leprae).
FNA carries the risk of fistula formation as does abscess
incision and drainage. Mycobacterial
infection is definitively diagnosed by culture. Cultures for
atypical mycobacteria may, however, be
negative even when infection is present. Only about 50% of
excised diseased lymph nodes will be
culture positive. With a mean time of about eight weeks for
culture and twelve weeks for sensitivity
results, initial diagnosis depends greatly on the clinical
features. Most atypical mycobacteria elicit
granulomatous inflammation with acid-fast bacilli, and many
establish cavitary disease difficult to
distinguish from TB. The histologic findings associated with
MAC vary considerably and range from
granulomas to nodular foam cell lesions to purulent and
necrotizing inflammations. Mantoux tests
for atypical mycobacteria are available and were at least
weakly positive in 95% of cases in the series
by Hawkins and colleagues. NTM-specific antigens have been
developed and are reported to be
extremely successful for diagnosis. Newer methods that use
polymerase chain reaction techniques
to detect mycobacterial RNA in tissue and M. avium
deoxyribonucleic acid in gastric aspirates are
still not widely available.
Chest x-ray findings are
typically absent. Contrast-enhanced CT images show asymmetric cervical lymphadenopathy with contiguous
low-density, necrotic, ring-enhancing masses involving the subcutaneous fat and skin. In addition,
inflammatory stranding of the subcutaneous fat characteristic of bacterial inflammation is
minimal or absent with NTM infection.
The treatment of choice is complete surgical excision of the
involved nodes. Medical treatment of
NTM with prolonged courses of antimicrobials is not well
established. Hawkins and colleagues
showed resolution of neck masses in 4 of 18 cases of
atypical mycobacterial infection with
chemotherapy alone. If excision is incomplete or disease
recurs, fluoro-quinolones (e.g.
ciprofloxacin), clarithromycin or azithromycin plus
ethambutol with rifampin should be used. If the
parotid gland is affected, a superficial parotidectomy with
facial nerve preservation is necessary.
Removal of involved skin is often necessary during excision.
Careful attention should be paid to
avoid any injury to the mandibular branch of the facial
nerve because it is often adherent to the
tract. Patients with otitis media caused by M abscessus
should receive clarithromycin plus an initial
course of amikacin plus cefoxitin. Surgical debridement may
be required.
