In antiphospholipid syndrome, individuals produce antiphospholipid antibodies, which attack the phospholipids in the cell membrane of their own cells, or attack proteins that are bound to those phospholipids.
So antiphospholipid syndrome, or APS, is an autoimmune disease.
Antiphospholipid syndrome can be primary or secondary. Primary antiphospholipid syndrome occurs by itself, whereas secondary antiphospholipid syndrome occurs with other autoimmune diseases, especially systemic lupus erythematosus.
And just like most autoimmune diseases, antiphospholipid syndrome is more common in young females.
The exact cause of antiphospholipid syndrome isn’t known, but there are some known genetic and environmental factors.
For instance, the HLA-DR7 gene encodes a specific type of a protein called major histocompatibility complex or MHC class II, which sits on the surface of the B cell.
These surface proteins help activate B cells so that they can start producing antibodies.
Now, having a mutated HLA-DR7 gene predisposes individuals to activate B cell production of antiphospholipid antibodies.
But the presence of the mutated HLA-DR7 gene alone isn’t enough to develop antiphospholipid syndrome - an environmental trigger must also be present.
There’s a variety of potential triggers - some common ones include infections - like syphilis, hepatitis C, HIV, and malaria - drugs, like some cardiovascular drugs - including procainamide, quinidine, propranolol, and hydralazine - or antipsychotic drugs like phenytoin and chlorpromazine.