The definitive evaluation of sarcoidosis

Molecular analysis of sarcoidosis tissues for mycobacterium species DNA

We performed polymerase chain reaction analysis, for Mycobacterium species 16S rRNA, rpoB, and IS6110 sequences, on 25 tissue specimens from patients with sarcoidosis and on 25 control tissue specimens consisting of mediastinal or cervical lymph nodes and lung biopsies. Mycobacterium species 16S rRNA sequences were amplified from 12 (48%) rpoB sequences and from 6 (24%) of the sarcoidosis specimens. In total, 16S rRNA or rpoB sequences were amplified from 15 sarcoidosis specimens (60%) but were not detected in any of the control tissues (p=0.00002, chi square). In three specimens, the sequences resembled Mycobacterium species other than M. tuberculosis. All specimens with sequences consistent with M. tuberculosis were negative for IS6110. We provide evidence that one of a variety of Mycobacterium species, especially organisms resembling M. tuberculosis, is found in most patients with sarcoidosis.

Mycobacterium tuberculosis DNA in tissue affected by sarcoidosis

OBJECTIVE

To investigate the prevalence of Mycobacterium tuberculosis DNA in granulomatous tissues from patients with sarcoidosis and from controls matched for age, sex, and tissue by using the polymerase chain reaction.

DESIGN

Single blind control trial.

SUBJECTS

16 patients with sarcoidosis who had undergone diagnostic biopsy of lung, skin, or lymph node and 16 patients with squamous cell carcinoma or Hodgkin's disease to act as controls. In addition, four lung specimens infected with M tuberculosis were included as positive controls.

RESULTS

M tuberculosis DNA was present in sarcoid tissues containing granulomas from seven of the 16 patients and one of the 16 matched controls. Two of the four specimens known to be infected with M tuberculosis were positive in the controlled experiment.

CONCLUSION

These figures suggest that M tuberculosis DNA is detected as readily in patients with sarcoidosis as in patients with frankly tuberculous tissues and imply that M tuberculosis may be linked to the cause of sarcoidosis.

Tuberculin sensitivity in tuberculosis

It is generally accepted that patients suffering from Mycobacterium tuberculosis infections show positive tuberculin skin tests, with certain rare exceptions. Recognized causes of these exceptions include extreme illness, whether due to extensive tuberculosis or to other severe disease, and certain viral infections, notably measles. It is not so generally recognized that a few patients with pulmonary tuberculosis, generally of rather indolent type, who are not acutely ill, persistently fail to react to tuberculin; and that the range of tuberculin sensitivity observed in patients with the more usual forms of tuberculosis is very wide.

The effect of cortisone in diminishing the size of tuberculin reactions in patients with pulmonary tuberculosis is directly related to the degree of sensitivity; reactions produced by small doses of tuberculin in patients with high sensitivity are greatly diminished or inhibited, while those produced by 100 T.U. in patients with low sensitivity are not significantly altered. Patients with tuberculosis can be desensitized to tuberculin by increasing injections of tuberculin under chemotherapy cover. In patients who have been so desensitized, the addition of cortisone to tuberculin in an intradermal test produces positive reactions in 70%. Among patients with sarcoidosis giving no reaction to 100 T.U., about half react when cortisone is added.

These observations show that in patients with sarcoidosis, a negative tuberculin test cannot be taken to exclude M. tuberculosis infection.