eMedicine Specialties > Dermatology > Mycobacterial Infections

Mycobacterium Avium-Intracellulare Infection

Author: Noah S Scheinfeld, MD, JD, FAAD, Assistant Clinical Professor, Department of Dermatology, Columbia University; Consulting Staff, Department of Dermatology, St Luke's Roosevelt Hospital Center, Beth Israel Medical Center, New York Eye and Ear Infirmary; Private Practice
Coauthor(s): Supriya Tomar, MD, Consulting Staff, Mohs College; Douglas W Kress, MD, Program Director, Medical Director of Clinical Services, Department of Dermatology, University of Pittsburgh Medical Center; Nicole Restauri, MD, Staff Physician, Radiology, University of Pittsburgh School of Medicine; Jessica M Allan, MD, Consulting Staff, Private Practice
Contributor Information and Disclosures

Updated: Jul 15, 2008

Introduction

Background

Mycobacterium avium-intracellulare (MAI, or MAC) is the atypical Mycobacterium most commonly associated with human disease. It is primarily a pulmonary pathogen that affects individuals with immune compromise secondary to AIDS, hairy cell leukemia, and immunosuppressive chemotherapy. In this clinical setting, MAI has been associated with osteomyelitis; tenosynovitis; synovitis; and disseminated disease involving the lymph nodes, the CNS, the liver, the spleen, and the bone marrow. Although the prevalence of MAI infection has increased following the AIDS epidemic, it remains a rare cause of skin disease. However, MAI has been found to cause cutaneous disease in individuals with immunocompetence and immunosuppression.
 
The eMedicine Infectious Diseases article Mycobacterium Avium-Intracellulare may provide additional information. Medscape CME courses that might be of interest are Nontuberculous Mycobacteria: Update on Diagnosis and Treatment and Infectious Complications Associated With Immunomodulating Monoclonal Antibodies Used in the Treatment of Hematologic Malignancy.

Pathophysiology

MAI is an acid-fast atypical Mycobacterium. The organism is ubiquitous in the environment, and it is the most common bacteria isolated from patients with AIDS. MAI causes cutaneous disease by 3 separate mechanisms, which occur in unique patient populations with different morphologic manifestations. MAI infection may involve the skin primarily via posttraumatic inoculation, secondarily as a manifestation of disseminated Mycobacterium avium-intracellulare (DMAI) systemic disease, and by direct extension as a complication of cervical lymphadenitis.

Primary cutaneous MAI infection generally occurs in hosts who are immunocompetent after traumatic introduction into the soft tissue. Local disease ensues, manifested primarily as nodules that may progress to ulcers. One case report described primary MAI infection resulting in a clinical picture resembling lupus vulgaris.¹ Disseminated disease most commonly occurs in individuals who are immunosuppressed, and hematogenous seeding of the skin may result in a wide variety of skin lesions, including nodules and abscesses, panniculitis,² folliculitis, and acute disease with hemorrhagic pustules.

MAI is the most common cause of pediatric cervical adenitis. Skin involvement in this setting is not uncommon and includes sinus track and abscess formation. Cervical adenitis rarely involves deeper structures, but it may result in extensive superficial destruction with cosmetic deformity.

Frequency

United States

In the United States, MAI infection is considered a nonreportable infectious disease. The US Centers for Disease Control and Prevention surveillance data from Houston and Atlanta suggest an incidence of 1 case per 100,000 persons per year. In 1994, the highest incidence of DMAI, 37,000 cases, was measured. Because DMAI infection often occurs in association with HIV, this was not surprising. Thus, the 1994 peak was coincident with the peak in the AIDS epidemic. One case series revealed cutaneous involvement in 6 of 30 cases of DMAI infection.

US Centers for Disease Control and Prevention data suggest that the incidence of MAI infection may be decreasing as a result of highly active antiretroviral therapy and antimicrobial prophylaxis. Primary cutaneous MAI infection is rare, with 12 cases reported in the literature prior to 1997. The degree to which skin involvement occurs as a sequela of cervical adenitis has not been well studied; however, the literature suggests that the risk of skin involvement increases with advanced disease.

Mortality/Morbidity

• Primary cutaneous involvement does not usually result in systemic disease and most often occurs in otherwise healthy individuals; therefore, the prognosis is favorable because treatment is generally curative.
• Disseminated disease resulting in cutaneous MAI infection occurs in individuals with underlying illnesses and may significantly increase morbidity in this population. Controversy remains regarding the impact of DMAI infection on life expectancy in patients with AIDS. However, untreated DMAI infection in this population is clearly associated with an increased mortality rate.
• Cervical adenitis may cause local destruction of superficial structures and may result in cosmetic and functional impairment without treatment, but dissemination beyond the primary site is rare.

Race

No racial predilection has been noted.

Sex

No sexual predilection has been noted.

Age

Cutaneous MAI infection has been reported in all age groups.

• Cervical adenitis most commonly affects children. One chart review series of 47 children with cervical adenitis revealed a median age of 3 years when the MAI infection was diagnosed by doctors.
• Most case reports of primary cutaneous MAI infection have been in individuals aged 2-10 years, although adult cases have been described.
• A literature review of 8 cases of cutaneous MAI infection occurring secondary to disseminated disease found a median patient age of 22.2 years, with a range of 2-28 years.

Clinical

History

Any history of the introduction of a foreign object (eg, needle, splinter) should be sought if MAI infection is suspected.

• Cutaneous MAI infection should be suspected when an individual who is immunocompromised presents with obscure skin lesions. Additional symptoms, including fatigue, fever, diarrhea, weight loss, back or bone pain, shortness of breath, and/or cough may suggest disseminated disease.
• Patients with MAI cervical adenitis may present with an indolent course of a unilaterally expanding mass in the neck.
• Fever and other constitutional symptoms are generally absent.
• Primary cutaneous MAI infection is most often the result of traumatic inoculation, although a specific history of trauma is generally absent.
• Patients may describe the development of a single nodule or multiple nodules progressing over time into ulcerative lesions with or without serosanguineous exudates. Nodules may be tender.
• Cutaneous MAI infection in an HIV-positive patient mimicking histoid leprosy has been reported.³
• Henoch-Schönlein purpura associated with pulmonary MAI complex infection has been noted.⁴
• MAI can be associated with osteomyelitis. Primary nontraumatic MAI complex osteomyelitis of the distal phalanx has occurred.⁵ Multifocal osteomyelitis caused by nontuberculous mycobacteria in patients with a genetic defect of the interferon-gamma receptor has been noted.
• Subcutaneous and muscular abscesses due to MAI can occur as a manifestation of immune restoration in patients with AIDS.
• Murdoch and McDonald⁶  reported MAI cellulitis occurring with septic arthritis after joint injection.

Physical

• Examination in the case of disseminated disease may reveal a patient who is febrile with positive findings on lung examination and with findings of hepatosplenomegaly; lymphadenopathy; swollen, tender joints or focal neurologic deficits in the setting of painful, erythematous, indurated subcutaneous plaques; painful nodules and ulcers; folliculitis; or hemorrhagic pustules.
• Patients with cervical adenitis due to MAI usually present with enlarged submandibular or submaxillary nodes.
• Skin abscess and sinus tracks may be present. Sporotrichoid spread of cutaneous MAI complex infection can occur.⁷
• Primary cutaneous MAI infection generally results in painful subcutaneous nodules and ulcers that occur on the extremities and the trunk. Lesions may be present in multiple stages of development, and nodules have been described as both flesh colored and purple-red.

Causes

MAI is the most common organism isolated from patients with AIDS.

• Immunosuppression is a risk factor for disseminated disease.
• Patients who are immunosuppressed and at risk for DMAI disease include those on immunosuppressive agents after undergoing transplantation and patients with leukemia and lymphoma.
• No risk factors for primary cutaneous MAI infection or cervical adenitis are known.

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