I read with interest the report by Mehta,1 regarding the utility of computed chest tomography (CT scan) in recurrent uvetis. This is a report of clinical interest, but there are certain points whose relevance needs clarification. In case report 1 the author says that a CT scan of chest is suggestive of tuberculous lymphadenopathy, whereas in discussion he says that a CT scan diagnosed active pulmonary tuberculosis. Both the statements are different because tuberculous lymphadenopathy in vast majority of patients produces no symptoms or signs unless routine radiological examination of chest is carried out at the appropriate time or serial tuberculin test shows conversion from negative to positive, whereas active pulmonary tuberculosis is a symptomatic disease and shows the symptoms of tuberculosis such as lassitude, malaise, impairment of appetite, loss of weight, evening rise of temperature, and many others. Although it is true that tuberculous uveitis is not an easy diagnosis to make, but on the basis of clinical sign, symptoms and investigations such as Mantoux test, X-ray chest PA view, and erythrocyte sedimentation rate (ESR), the diagnosis of uveitis owing to tuberculosis can be made.2 As in case 1, Mantoux test is strongly positive with induration of 34 x 20 mm. Studies have shown that those who react with 20 mm or more induration have more chances of developing tuberculosis.3 Positive Mantoux test indicates that the person is infected by Mycobacterium tuberculosis. It does not prove that the person is suffering from the disease. According to current concept, an individual showing and induration of 10 mm or more is considered positive indicating infection with M. tuberculosis. As the author says that conventional X-ray images the mediastinum inadequately owing to interference of the sternum and soft tissues such as trachea and esophagus, but the hilar lymphnodes are visible in X-ray chest PA view in this case. As in case 1, the left eye has glaucomatous disk damage which is manifested by the cup-disk ratio of 0.9 with rim pallor and intraocular pressure of 34 mm Hg. In such condition the vision of 20/40 seems to be unlikely.
The author says that case 2 has uveitis owing to sarcoidosis. Most common manifestation of sarcoidosis is enlargement of hilar lymph node, which can be seen in X-ray chest PA view. Diagnosis of sarcoidosis can be made by clinical features and X-ray chest. In most cases skin sensitivity to tuberculin is depressed or absent and mantoux reaction is therefore a useful “screening” test, a strongly positive reaction to 1 TU virtually excludes sarcodosis but the diagnosis can be confirmed by biopsy of a superficial lymph node or of a skin lesion. Kviem test is also useful diagnostic procedure.4 Diagnosis of sarcoidosis can be confirmed by biopsy, but not by CT scan.
In a country like India, which is a developing country, most people belong to the lower socioeconomic class and cannot afford costly investigations such as a CT scan. In remote areas or even at most district headquarter levels CT scan facility is not available. We can make the diagnosis of uveitis owing to tuberculosis and to sarcoidosis on the basis of clinical features and investigations which are not costly, such as X-ray chest PA view, ESR, Mantoux test, and biopsy of lymph node.
As the author says, mediastinal lymphadenopathy has been well described in numerous conditions including systemic infections (tuberculosis) and autoimmune disorders (lymphomas, leukemia). So with the help of CT scan alone we cannot confirm the diagnosis. Clinical sign symptoms and other investigations are a must.
1. Mehta S. Utility of computed chest tomography (CT scan) in recurrent uveitis Indian J Ophthalmol. 2004;52:321–2
2. Peyman , Sanders , Goldberg , Uveitis Principles and Practice of Ophthalmology. 1987;2:1593–95
3. Park JE, Park K. Tuberculin Test Textbook of Social and Preventive Medicine. 1986;11:168–69
4. John Macleod. Diseases of respiratory system Davidson's Principles and Practice of Medicine. 1982;13:294