Pathology of the Thymus 



ANDRE CROTTI 



COLUMBUS 



Thyroid Aplasia and Hypoplasia, According to several authors, 

 absence of the thymus, or even thymus hypoplasia, are causes of mental 

 disturbances in children. In 28 mentally defective cases Bourneville 

 found the thymus absent. Basing his conclusions upon a large number of 

 autopsies of mentally defective children, he found that in 70 per cent 

 the thymus was absent. Although not contending that any one type of 

 case can be referred to the deficiency of one organ, Sajous (b) believes that 

 the deficient activity of the thymus results in deficiency of nucleins sup- 

 plied, to the brain through the lymphocytes, thus causing idiocy. Harrower 

 (c) makes the statement that thymus hypoplasia is found in conjunction 

 with defectiveness and with a hypoplastic type of individual. 



Pathological Involution or Atrophy. There are two forms of involu- 

 tion, the physiological and the pathological. 



The physiological involution belongs to the chapter on Physiology. 



Pathological involution may occur without any apparent cause or may 

 occur in conjunction with chronic conditions or infections such as maras- 

 mus, tuberculosis, empyema, etc. This pathological involution is most 

 likely due to some intoxication or irritation centering upon the thymus. 

 Adipose cells disappear; the arteries and veins show signs of endarteritis, 

 and the cortical and medullary substances are no longer easily differen- 

 tiated. The lymphoid cells are more or less absent and are replaced by 

 fibroblastic and endothelial ccdls resembling, in many respects, those found 

 in the HassalPs corpuscles. The eosinophiles are diminished. The Has- 

 sall's corpuscles are somewhat increased in size and number, but show 

 retrogressive changes. 



Atrophy may become so marked as to obtain a complete sclerosis of 

 the thymus. 



Active and Passive Congestions. (Edema and Hemorrhage.) Active 

 and passive congestions of the thymus may occur under the most varied 

 conditions ; as a result, the thymus becomes enlarged and reddened. Such 

 a congestive enlargement may be mistaken at autopsy for a real thymic 

 hyperplasia. There is no doubt that such congestions play a very promi- 

 nent part in suffocation due to thymic hyperplasia and to other reasons. 



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