A fatal case of saddle pulmonary embolism: Is it due to hump-nosed viper envenomation?

Hump-nosed viper (HNV) bites are a common occurrence in Sri Lanka, and systemic envenomation followed by acute renal failure (ARF) and Micro Angiopathic Haemorrhagic Anaemia (MAHA) are well-documented complications. But pulmonary thromboembolism has never been reported. A 56-year-old previously healthy gentleman presented following an HNV bite with the complaint of pain at the site. On examination, fang marks were observed over the left 4^th toe with local reaction. His initial clotting profile was unremarkable, but he got deranged on the third day, complicated with low urine output. While he was on peritoneal dialysis on the 9^th day, he suddenly developed shortness of breath and expired. The autopsy revealed local necrosis over the bite site, indwelling saddle pulmonary thrombus and bilateral deep vein thrombosis. There was macroscopic and microscopic evidence of ARF. The histology of the lungs was suggestive of pulmonary hypertension. Effects of HNV bites range from local features to systemic envenomation like venom induced coagulopathy, thrombotic microangiopathy and ARF. Venom contains mild procoagulant and phospholipase activity, giving rise to MAHA. But deep vein thrombosis followed by pulmonary embolism (PE) has never been reported for HNV bites. The etiology of PE could be due to the shared effects of undiagnosed pulmonary hypertension, prolonged bed rest and venom induced coagulopathy. Systemic envenomation is not uncommon with HNV bites complicated with ARF and MAHA. Since PE has not been documented earlier as a complication, it is suggested that the possible association with future research, though there were a few other risk factors involved.