Distortion in transmission of pathogenic SDHB- and SDHD-mutated alleles from parent to offspring.

Phaeochromocytoma and paraganglioma are highly heritable tumours; half of those associated with a germline mutation are caused by mutations in genes for Krebs's cycle enzymes, including succinate dehydrogenase (SDH). Inheritance of SDH alleles is assumed to be Mendelian (probability of 50% from each parent). The departure from transmission of parental alleles in a ratio of 1:1 is termed transmission ratio distortion (TRD). We sought to assess whether TRD occurs in the transmission of SDHB pathogenic variants (PVs). This study was conducted with 41 families of a discovery cohort from Royal North Shore Hospital, Australia, and 41 families from a validation cohort from St. Bartholomew's Hospital, United Kingdom (UK). Inclusion criteria were a clinically diagnosed SDHB PV and a pedigree available for at least two generations. TRD was assessed in 575 participants with the exact binomial test. The transmission ratio for SDHB PV was 0.59 (P = 0.005) in the discovery cohort, 0.67 (P < 0.001) in the validation cohort, and 0.63 (P < 0.001) in the combined cohort. No parent-of-origin effect was observed. TRD remained significant after adjusting for potential confounders: 0.67 (P < 0.001) excluding families with incomplete family size data; 0.58 (P < 0.001) when probands were excluded. TRD was also evident for SDHD PVs in a cohort of 81 patients from 13 families from the UK. The reason for TRD of SDHB and SDHD PVs is unknown, but we hypothesize a survival advantage selected during early embryogenesis. The existence of TRD for SDHB and SDHD has implications for reproductive counselling, and further research into the heterozygote state.

Diagnosis of spontaneous secondary tension pneumothorax following apparent recovery from coronavirus disease 2019 pneumonitis: a case report.

BACKGROUND: Coronavirus disease 2019 has been associated with a plethora of different manifestations of systems affected (including pulmonary, gastrointestinal, and thrombotic disease) and time to presentation of complications. Pneumothorax has been established as a complication in the literature. However, tension pneumothorax remains a rare presentation with higher mortality. We report a case of secondary tension pneumothorax in a patient following apparent recovery from coronavirus disease 2019 pneumonitis. CASE PRESENTATION: Eight days after resolution of coronavirus disease 2019 pneumonitis symptoms, a 51-year-old Caucasian man with no pre-existing pulmonary disease was brought into the emergency department following 48 hours of progressive shortness of breath. Further clinical assessment revealed reduced breath sounds in the right lung, blood pressure was 116/95 mmHg, and jugular venous pressure was not elevated. Chest x-ray showed right-sided tension pneumothorax with mediastinal shift. Insertion of a chest drain led to rapid resolution of symptoms, and the patient was discharged following full re-expansion of the lung. CONCLUSIONS: The period of recovery from coronavirus disease 2019 is variable. Clinicians should consider tension pneumothorax as a possible complication of coronavirus disease 2019 pneumonitis in patients presenting with type 1 respiratory failure, even after resolution of pneumonitis symptoms and a considerable time period following initial contraction of coronavirus disease 2019.