Ameloblastic fibroma with extensive dentinoid - A rare presentation.

Ameloblastic fibroma (AF) is a rare benign odontogenic tumour first described by Kruse in 1891. Although reported in a wide age range, most of the cases are seen in the first two decades of life with majority of cases being diagnosed before the age of 20 years. There are reported variations in the histopathological presentation of ameloblastic fibroma. In this case report, we present a case of ameloblastic fibroma with extensive dentinoid formation involving the mandible in an 8-year-old male patient which clinically presented as an aggressive lesion.

Are WHO approved nucleic acid amplification tests causing large-scale "false identification" of rifampicin-resistant tuberculosis?: Programmatic experience from south india.

INTRODUCTION: The nucleic acid amplification tests (NAATs): Line probe assay and GeneXpert (Xpert) have evolved as the primary tool for identification of rifampicin (RIF)-resistant (RR) tuberculosis (TB) worldwide, primarily because of the ease and speed. We rechecked RR isolates identified by NAATs from presumptive RR TB cases belonging to South India by the Revised National TB Control Program, India using multiple RIF concentrations on Bactec MGIT system and compared the mutation patterns with the resistance levels. METHODOLOGY: Standard protocol for Bactec MGIT system as given by the manufacturer modified for the multiple RIF concentrations was used. All the retests were done in a certified BSL3 laboratory. RESULTS: We found that there is a mismatch of up to 20% (RIF breakpoint 0.5 mg/L); the NAATs probably overidentifying RR TB. Half of the cases with mismatch showed a sub-breakpoint rise in resistance level (0.125 mg/L to 0.5 mg/L RIF). DISCUSSION AND CONCLUSION: The probable reasons for the mismatch are "sub-breakpoint low-level resistance mutants," hetero-resistant bacterial populations, and other inherent test limitations along with the low RR TB prevalence in South India (<5%) among "presumptive multidrug-resistants." This could be due to the incomplete selection pressure by an inadequate RIF exposure caused by various factors including a low-RIF dosage being used widely and poor Directly observed treatment. To prevent the false diagnosis of RR TB in a massive scale when using NAATs, we may need to enforce a carefully targeted testing approach and a phenotypic susceptibility testing with multiple RIF concentrations for confirmatory purposes.