Severe acquired haemophilia associated with asymptomatic SAR
Haemophilia A can present in patients as either congenital or acquired. While the differences in pathophysiology are intuitive, patients with congenital haemophilia A have a 20%–40%?chance of developing antibodies to factor VIII during their lifetime usually in the setting of treatment. Contrasting this are patients who develop acquired haemophilia A, which is a rare disorder involving spontaneous development of these autoantibodies, which occur at a rate of one case/million/year.

With the novel SARS-CoV-2 virus, there is often a predilection for prothrombotic states; however, it has also been rarely associated with acquired haemophilia A. Here, authors present a case of severe acquired haemophilia A requiring massive blood transfusions in a patient who had an otherwise asymptomatic SARS-CoV-2 infection.

A 65-year-old man presented with symptoms of severe subcutaneous bleeding in his arm, which led to compartment syndrome requiring fasciotomy and massive blood transfusion protocol. Medical history was significant for history of autoimmune thyroid disease. Workup revealed elevated partial thromboplastin time, decreased factor VIII levels and elevated factor VIII inhibitor levels. He was worked up for causes of acquired haemophilia A and was found to have an elevated SARS-CoV-2 antibody level. Given his negative workup for other secondary aetiologies, we suspect that the cause of his haemophilia A was from his SARS-CoV-2 infection, which has been observed previously in various case reports.

Learning points:
Acquired haemophilia A is a rare, but serious condition involving autoantibodies to factor VIII, which can be caused by infections, autoimmune diseases, malignancies and drugs.

This case suggests that asymptomatic SARS-CoV-2 infections, and their potential for associated autoimmune phenomena, can be associated with acquired haemophilia A and checking serology for SARS-CoV-2 may be helpful to elucidate potential causes.

Patients with a history of autoimmune conditions may be more predisposed to some of the autoimmune phenomena seen in SARS-CoV-2 infections.