January 2007

Fig.3

Fig.4

Diagnosis: Atypical mycobacteria

Histopathology: The biopsy revealed transepidermal necrosis and dilated vasculature in the superficial dermis filled with atypical lymphocytes and scattered neutrophils. Abundant AFB positive bacilli were identified by AFB stain (figure 3 and 4).

Tissue Biopsy Culture:
Mycobacterial culture of the biopsied sample revealed acid fast bacilli. Since it was probed negative for M. tuberculosis and M. avium complex, this is most consistent with atypical mycobacterial infection other than M. avium complex. The sample was sent to Missouri tuberculosis reference laboratory for further speciation.

Patient course:
Patient was started on clarithromycin 500mg twice a day empirically and symptoms were greatly improved after 2 months. We are still waiting for the final result of speciation.

Discussion:
Atypical mycobacteria are defined as acid-fast mycobacteia that do not cause tuberculosis or leprosy. They exist in a variety of natural sources, such as soil, water and animals. Most human disease is acquired from the environment. There are increasing numbers of report of atypical mycobacteria in immunosuppressed patients, especially AIDS patients. The most common species of atypical mycobacteria related to cutaneous diseases are M. ulcerans, M. marinum and M. chenlonae. However, M. avium-intracellulare complex is common in AIDS patients (1, 2). Atypical mycobacteria are perhaps the most difficult opportunistic infection to diagnose because they present with nonspecific and subtle clinic pictures, usually indolent ulcers, nodules and plaques (3).

Typical histological findings for atypical mycobacterial infection include epidermal hyperplasia or ulceration, sometimes with neutrophilic microabscesses, supprative granulomas and diffuse dermal mixed infiltrate of neutrophilis, histocytes and plasma cells. AFB stains positive for acid fast bacilli and sometimes there is prominent fibrosis (4, 5).

Therapy varies depending on the causative organism. Combination antibiotics are commonly required. Surgical excision is another option for localized disease. The prognosis is generally good with proper antibiotic or surgical treatment.

References:

1. Andrew's diseases of the Skin Clinical Dermatology Tenth Edition Elsevier Inc, 2006.

2. Dermatology. Jean Bolognia, Joseph L Jorizzo, Ronald P Rapini. Elsevier Inc., 2003.

3. Czelusta, A. and Moore, A. Cutaneous Mycobacterium kansasii infection in a patient with systemic lupus erythematosus: Case report and review J Am Acad Dermatol. 1999 Feb;40(2 Pt 2):359-63

4. Bartralot, R. et al. Cutaneous infections due to nontuberculous mycobacteria: histopathological review of 28 cases. Comparative study between lesions observed in immunosuppressed patients and normal hosts. J Cutan Pathol. 2000 Mar;27(3):124-9

5. Practical Dermatopathology. Ronald Rapini Elsevier Mosby Inc., 2005.

This case is presented by Drs. Wei-Wei Huang, Beatriz Tapia, Alison Klenk and Ann Lind