Hsiao Pa-Fan, Tzen Chin-Yuan, Chen Hsiu-Chin, Su Hsin-Yi
Department of Dermatology, Mackay Memorial Hospital, Taipei, Taiwan.
Int J Dermatol. 2003 Apr;42(4):281-6. doi: 10.1046/j.1365-4362.2003.01461.x.
Cutaneous tuberculosis is especially difficult to distinguish from other granulomatous dermatoses. We used polymerase chain reaction (PCR) to evaluate the incidence of cutaneous tuberculosis and atypical mycobacterial infection in formalin-fixed, paraffin-embedded tissues with unspecified granulomatous inflammation and negative results for acid-fast bacilli (AFB), and analyzed the pattern of cutaneous tuberculosis in this group of patients.
A total of 38 specimens which had been collected from 36 patients and fulfilled the criteria for tissues described above were used in this study. Two different primer pairs targeting the gene encoding for 16S ribosomal RNA (common to all mycobacteria) and the insertion sequence IS6110 (specific for M. tuberculosis complex) were used in the PCR assays. The clinical characteristics, histopathologic findings, and culture results of the patients were also analyzed.
Four specimens were excluded from the analysis due to the lack of internal control testing. Of the remaining 34 specimens, 22 were PCR positive for the 16S rRNA gene. Among them, 18 specimens were PCR positive for both the 16S rRNA gene and IS6110. Cutaneous tuberculosis could be diagnosed in these 18 cases (56.2%). Out of the 18 cases, there were 8 women and 10 men. The age range was 15-77 years (mean: 44.2 years). After reviewing their clinical presentation, 11 cases were considered as tuberculosis verrucosa cutis, 6 cases as lupus vulgaris, and 1 case as erythema induratum. The remaining 4 cases (12.5%) positive only for 16S rRNA gene were considered as possible atypical mycobacteria infection.
These results show that in paucibacillary form of cutaneous tuberculosis with unclassical clinical and histological presentation, this PCR system provides rapid and sensitive detection of M. tuberculosis DNA in formalin-fixed, paraffin-embedded specimens. Cutaneous tuberculosis represents a significant proportion in specimens showing granulomatous inflammation. In areas like Taiwan, where prevalence of pulmonary tuberculosis is still high, tuberculosis verrucosa cutis and lupus vulgaris are common forms of cutaneous tuberculosis and are seen more frequently than atypical mycobacterial infection.
皮肤结核尤其难以与其他肉芽肿性皮肤病相区分。我们运用聚合酶链反应（PCR）来评估在福尔马林固定、石蜡包埋组织中，非特异性肉芽肿性炎症且抗酸杆菌（AFB）检测结果为阴性的皮肤结核及非典型分枝杆菌感染的发生率，并分析该组患者的皮肤结核模式。
本研究共使用了从36例患者收集的38份符合上述组织标准的标本。在PCR检测中使用了两对不同的引物对，分别靶向编码16S核糖体RNA的基因（所有分枝杆菌共有）和插入序列IS6110（结核分枝杆菌复合群特异性）。还分析了患者的临床特征、组织病理学发现及培养结果。
由于缺乏内部对照检测，4份标本被排除在分析之外。在其余34份标本中，22份16S rRNA基因PCR检测呈阳性。其中，18份标本16S rRNA基因和IS6110均PCR检测呈阳性。这18例（56.2%）可诊断为皮肤结核。在这18例中，女性8例，男性10例。年龄范围为15 - 77岁（平均：44.2岁）。回顾其临床表现后，11例被认为是疣状皮肤结核，6例为寻常狼疮，1例为硬结性红斑。仅16S rRNA基因呈阳性的其余4例（12.5%）被认为可能是非典型分枝杆菌感染。
这些结果表明，在临床和组织学表现不典型的少菌型皮肤结核中，该PCR系统能快速、灵敏地检测福尔马林固定、石蜡包埋标本中的结核分枝杆菌DNA。在显示肉芽肿性炎症的标本中，皮肤结核占相当比例。在台湾等地，肺结核患病率仍然较高，疣状皮肤结核和寻常狼疮是皮肤结核的常见形式，且比非典型分枝杆菌感染更常见。
