Exaggerated delayed type hypersensitivity reaction in the TST leading to a permanent scar. The upper panel represents results of the TST in a 14-year-old boy with LTBI, A taken three days, B two weeks and C three months after inoculation of 2 TU of PPD RT23. The original size of the induration was 20 mm. Photos: Courtesy of Dr. Peter Floman, Hospital of Porvoo. The lower panel represents results of the TST in a 13-year old girl with TB lymphadenitis, D taken 3 days and E two weeks after performing TST. This child was not enrolled in the current study.