Pulmonary lymphatics in SIDS--a comparative morphometric study

Pulmonary lymphatics in a group of SIDS cases were compared with a control group of a similar age distribution. The causes of death in the controls were known to be associated with varying degrees of pulmonary edema. The surface areas of pleural, interstitial, peribronchial, periarterial and perivenous lymphatics were planimetrically measured. The data were statistically tested. The tests showed that the pulmonary lymphatics of the SIDS group were significantly more distended than those of the control group as expressed by highly significant differences in their surface areas. On the whole 2142 lymphatics were measured; 1255 in the SIDS group, which consisted of slides from 10 cases and 887 in the control group which consisted of slides from 11 controls. Although the sample size imposes a limit on the general applicability of the results, the clear distinction between the two groups as shown by the tests do indicate a possible feature of SIDS--lymphatic stasis--which might be secondary to some impairment of lymphatic drainage. This in turn could induce subtle fibrotic changes in the connective tissue framework of these lungs. The results are presented in the light of the forensic significance of the signs of asphyxia frequently found in SIDS and the diagnostic difficulties encountered in differentiating between SIDS and mechanical asphyxia e.g. due to smothering.