THE COURSE OF INFECTIOUS DISEASE 



4. Sarcoidosis 



One of the most interesting current problems in aetiology 

 is sarcoidosis. This is a chronic and usually benign disease 

 which is diagnosed essentially by the histological demonstra- 

 tion of the typical granuloma composed of epithelioid cells, 

 occasional Langhan's-type giant cells with some infiltration 

 with lymphocytes — which, however, is much less than is 

 usually seen with tuberculosis nodules — and showing plasma 

 cells in many instances. The main lesions are likely to be found 

 in the lymph nodes at the hilum of the lungs (Smellie and 

 Hoyle, 1957; Lofgren, 1953). During the height of the 

 disease, granulomatous lesions are widespread in the body 

 and a useful method of histological diagnosis is by liver 

 biopsy. In Smellie and Hoyle's series of 66 patients who 

 showed radiological evidence of enlarged hilar lymph nodes 

 when first seen, 21 showed the development of radiologically 

 visible lesions in the lung fields, followed in the majority (12) 

 by a return to normal appearances. The other common 

 manifestations are erythema nodosum and skin sarcoids, and 

 uveitis, but lesions may on occasion be found in almost any 

 organ. Generalized lymph-node enlargement is common. 



The relation of sarcoidosis to tuberculosis has been widely 

 discussed. At the present time it is probably correct to say 

 that a majority of writers favour the opinion that sarcoidosis 

 represents a result of infection with the tubercle bacillus. 

 Others would consider the association with tuberculosis non- 

 essential and regard the disease as a special type of reactivity 

 which might be called into play by a variety of stimuli. In 

 the majority of patients the Mantoux test is negative, or 

 positive only with a large dose, but a considerable minority 

 show a positive test to a small dose of tuberculin. Tubercle 

 bacilli are present from the lesions and a positive culture will 

 usually be taken as rendering the diagnosis of sarcoid highly 

 unlikely. The only laboratory type of aid to diagnosis is the 

 Kveim test. This is an intradermal inoculation of a heated 



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