Pulmonary tumor thrombotic microangiopathy (PTTM) causing fatal pulmonary hypertension is a rare presentation of malignancy. In general, patients with PTTM rapidly succumb to death due to severe hypoxia. To date, very few cases of PTTM have been reported in the literature; and most of these cases were from gastric cancer and were diagnosed on post mortem autopsy, as it is extremely challenging to make an ante mortem diagnosis. We here report on a case of undiagnosed diffuse gastric cancer, presenting as worsening hypoxia. The clinical, radiographic, and echocardiographic features, and laboratory and pathological results were consistent with PTTM from gastric cancer. The patient was started on anticoagulation therapy, corticosteroids, and high-flow oxygen. However, her hypoxia worsened to the extent that she required ventilator support, and she died soon after intubation due to cardiac arrest. Since diffuse gastric cancer is associated with hereditary diffuse gastric cancer syndrome, cadherin 1 gene mutation analysis was performed to estimate the risk to her daughters. The test came back negative.
Adrenal Cortex Hormones ; Anoxia* ; Ants ; Autopsy ; Cadherins ; Diagnosis ; Echocardiography ; Heart Arrest ; Humans ; Hypertension, Pulmonary ; Intubation ; Nuclear Family ; Oxygen ; Stomach Neoplasms* ; Thrombotic Microangiopathies* ; Ventilators, Mechanical

Eumelanin is a heteropolymer that is generally composed of hydroxylated indole residues and plays diverse protective functions in various species. Melanin is derived from the amino acid tyrosine and production of melanin is a highly complex oxidative process with a number of steps that can either proceed enzymatically or non-enzymatically. Although melanin plays important protective roles in many species, during melanization, particularly in steps that can proceed non-enzymatically, many toxic intermediates are produced, including semiquinones, dopaquinone, indole-quinones and moreover, the production of many reactive oxygen species. To mitigate the production of reactive species, a number of proteins that regulate the biochemical process of melanization have evolved in various living species, which is closely related to adaptation and physiological requirements. In this communication, we discuss differences between non-enzymatic and enzymatic processes of melanization and the enzymatic regulation of melanization in difference species with an emphasis on differences between mammals and insects. Comparison between melanization and insect sclerotization is also emphasized which raises some interesting questions about the current models of these pathways.
Animals ; Biological Evolution ; Humans ; Insecta ; metabolism ; Mammals ; metabolism ; Melanins ; biosynthesis ; chemistry ; Models, Biological ; Species Specificity