Cutaneous tuberculosis in Hong Kong: an update.

OBJECTIVE To provide an update on cutaneous tuberculosis in Hong Kong. DESIGN Retrospective study. SETTING Social Hygiene Service (Dermatology Division), the largest dermatological referral centre in Hong Kong. PATIENTS Patients presented with cutaneous tuberculosis between 1993 and 2002 inclusive. Case notes, histology reports, and microbiological reports were reviewed with particular reference to the epidemiology, duration of illness, history of contact with tuberculosis, culture results, and response to treatment. RESULTS There were 147 patients with cutaneous tuberculosis; among these a few had true cutaneous tuberculosis (n = 16) and the remainder were tuberculids (n = 131). In all they accounted for 0.04% of new dermatology cases diagnosed. Cases of cutaneous tuberculosis were distributed as follows: lupus vulgaris (n = 6, 4%), tuberculosis verrucosa cutis (n = 6, 4%), tuberculosis of the skin unclassified (n = 2, 1%), and orificial tuberculosis (n = 2, 1%). Culture and polymerase chain reaction was positive in less than half of the latter cases. All responded well to anti-tuberculosis therapy. Erythema induratum was the most common form (n = 127, 86%), but papulonecrotic tuberculids (n = 4, 3%) were uncommon. Erythema induratum affected the lower limb in all patients, with a female predominance, and responded to isoniazid monotherapy, multidrug anti-tuberculosis therapy, or doxycycline. CONCLUSION Lupus vulgaris and tuberculosis verrucosa cutis remain the commonest forms of true cutaneous tuberculosis, and erythema induratum is the most common tuberculid. Culture and polymerase chain reaction are positive in a small proportion of patients.