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Atypical mycobacterial cutaneous infections in Hong Kong: 10-year retrospective study
MH Ho, CK Ho, LY Chong
Social Hygiene Service (Dermatology Division), Department of Health, Yau Ma Tei Dermatology Clinic, 12/F Yau Ma Tei Specialist Clinic Extension, 143 Battery Street, Yau Ma Tei, Hong Kong
OBJECTIVE. To review the epidemiology of atypical
mycobacterial cutaneous infection in Hong Kong.
DESIGN. Retrospective study.
SETTING. Social Hygiene Service (Dermatology Division),
the largest dermatological referral centre in Hong Kong.
PATIENTS. Patients with a diagnosis of atypical
mycobacterial cutaneous infection based on clinical features, histopathology,
with or without a positive culture during the period 1993 to 2002.
MAIN OUTCOME MEASURES. Epidemiological data, clinical
features, histology, microbiological investigation, and treatment
response.
RESULTS. Of 345 394 dermatological cases presented
over the 10-year period, 33 (0.0096%) cases (19 male, 14 female)
of atypical mycobacterial cutaneous infection were diagnosed. The
most common type of infection was caused by Mycobacterium marinum
(n=17, 51.5%), followed by Mycobacterium avium-intracellulare
(n=3, 9.1%) and Mycobacterium chelonae (n=2, 6.1%). The upper
limb, especially the hands and fingers, was the most common (69.7%)
site of involvement. Tissue culture was positive in 18 (54.5%) cases.
All biopsies showed granulomatous histology. Thirty-two patients
received treatment and 31 responded. Twenty-six were treated with
oral tetracycline group of antibiotics (minocycline, doxycycline,
tetracycline). The duration of treatment ranged from 8 to 54 weeks
(mean, 24 weeks). Mild transient adverse effects to treatment were
reported in six cases.
CONCLUSION. Atypical mycobacterial infection is
rare in Hong Kong. Because of the low sensitivity of traditional
culture techniques, atypical mycobacterial infection may be underdiagnosed
if only culture-confirmed cases are included. Polymerase chain reaction
provides a rapid and sensitive method to improve diagnostic accuracy.
Tissue culture is crucial to determine antimicrobial susceptibility.
In our study, tetracycline group of antibiotics, especially minocycline,
was an effective treatment, particularly in cases caused by Mycobacterium
marinum.
Hong Kong Med J 2006;12:21-6
Key words: Mycobacterial infections, atypical; Mycobacterium marinum; Polymerase chain reaction; Skin diseases, bacterial
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