Comment on: Proposal for a new diagnostic classification of photodistributed Stevens-Johnson syndrome and toxic epidermal necrolysis

Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and SJS/TEN overlap (SJS/TEN), collectively referred to SJS/TEN, form a spectrum of severe life-threatening adverse drug reactions whose pathomechanism is not fully understood. The article "Photodistributed Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis: A Systematic Review and Proposal for a New Diagnostic Classification" by McKinley et. al., discusses a distinct distribution of epidermal necrosis in SJS/TEN, attributable to preceding exposure to ultraviolet radiation (UVR), and relative sparing of photo-protected areas. After reviewing numerous cases within the Immune-mediated Adverse drug Reactions in African HIV endemic setting Register and Biorepository (IMARI-SA) at the University of Cape Town with a similar clinical pattern as those published by McKinley et. al., we propose that the relative sparing of some areas giving an impression of photo-distribution is due to localised increase in skin pressure that reduces the blood supply in that area below a critical threshold. A dip in blood supply below this critical threshold quantitively limited T lymphocytes and cytokines that drive SJS/TEN to reach and damage the skin.

Clinical characteristics and histopathology of COVID-19 related deaths in South African adults

Comparisons of histopathological features and microbiological findings between decedents with respiratory symptoms due to SARS-CoV-2 infection or other causes, in settings with high prevalence of HIV and Mycobacterium tuberculosis (MTB) infections have not been reported. Deaths associated with a positive ante-mortem SARS-CoV-2 PCR test and/or respiratory disease symptoms at Chris Hani Baragwanath Academic Hospital in Soweto, South Africa from 15th April to 2nd November 2020, during the first wave of the South African COVID-19 epidemic, were investigated. Deceased adult patients had post-mortem minimally-invasive tissue sampling (MITS) performed to investigate for SARS-CoV-2 infection and molecular detection of putative pathogens on blood and lung samples, and histopathology examination of lung, liver and heart tissue. During the study period MITS were done in patients displaying symptoms of respiratory disease including 75 COVID-19-related deaths (COVID+) and 42 non-COVID-19-related deaths (COVID-). The prevalence of HIV-infection was lower in COVID+ (27%) than in the COVID- (64%), MTB detection was also less common among COVID+ (3% vs 13%). Lung histopathology findings showed differences between COVID+ and COVID- in the severity of the morphological appearance of Type-II pneumocytes, alveolar injury and repair initiated by SARS-CoV-2 infection. In the liver necrotising granulomatous inflammation was more common among COVID+. No differences were found in heart analyses. The prevalence of bacterial co-infections was higher in COVID+. Most indicators of respiratory distress syndrome were undifferentiated between COVID+ and COVID- except for Type-II pneumocytes. HIV or MTB infection does not appear in these data to have a meaningful correspondence with COVID-related deaths.