Antithrombin Pittsburgh: an alpha1-antitrypsin variant causing hemorrhagic disease

Area of Science:

• Hematology
• Biochemistry
• Genetics

Background:

• A 10-year-old boy presented with a severe, lifelong hemorrhagic disorder requiring extensive medical intervention.
• Previous laboratory tests indicated prolonged bleeding and clotting times, suggesting a complex coagulation defect.

Observation:

• The patient's condition was attributed to a potent inhibitor targeting the thrombin-fibrinogen reaction.
• This inhibitor exhibited characteristics similar to heparin but lacked key properties like barium citrate adsorption and protamine sulfate neutralization.

Findings:

• The inhibitory activity was localized to the alpha1-globulin fraction of the patient's blood.
• Immunological and functional analyses identified the inhibitor as a double-banded alpha1-antitrypsin with a novel phenotype.
• Trypsin and heterologous anti-alpha1-antitrypsin antibodies were found to reduce the inhibitor's effects.

Implications:

• This discovery expands the known spectrum of alpha1-antitrypsin phenotypes and their clinical manifestations.
• Understanding this unique inhibitor may lead to novel diagnostic approaches and therapeutic strategies for rare bleeding disorders.
• Further research into this specific alpha1-antitrypsin variant could elucidate new mechanisms in coagulation regulation.