There are only a few studies regarding the causes of treatment failure for tuberculosis. Therefore, this study aimed to determine the causes of intractable tuberculosis.

M.tuberculosis, differentiated MOTT (Tycobacterium Other Than Tuberculosis) were isolated, and the RFLP (Restriction fragments length polymorphisms) pattern was analyzed from 204 patients with pulmonary tuberculosis and 53 suffering from neck tuberculosis. The IL-1β, IL-12, *1 IFNγ and *2 TNFαblood levels were measured. All patients were regularly followed for 18 months after treatment.

There was no correlation between the RFLP patterns of M.tuberculosis treatment failure. From the 204 cases, 31.9% were intractable. The characteristics of patients with intractable tuberculosis were old age, being male and recurrent cases. The causes of treatment failure were identified as follows ; a decrease in the IL-12(59.4%) concentration, drug resistant strain(54.7%), irregular medication(15.4%), MOTT(6.2%) and a heavy infection(4.6%). The causes of all cases of intractable tuberculosis could be investigated. The IL-12 concentration in the blood was significantly lower in the intractable cases, where it disclosed a maximum sensitivity(64.7%) and specificity(75.4%) at 165.0 pg/ml. Most of the 53 cases on neck node tuberculosis were treated successfully. Therefore, we were unable to analyze the cause of treatment failure.

A decrease in the blood IL-12 concentration and drug resistant strains were identified as the most significant causes of treatment failure for tuberculosis. In Korea, infection by clusters were prevalent, but no difference in the clinical course between clusters and non-clusters could be found.