Haemophilia A and Haemophilia B clinically present very similarly, with bleeds into joints and muscles.
Both are inherited in an X-linked recessive way but 1/3 of cases will have no family history.
Both cause raised aPTT.
Haemophilia A = lack of factor VIII
Haemophilia B = lack of factor IX = Christmas disease
Treatment is with desmopressin and tranexamic acid. Major bleeds may need recombinant factor VIII. Avoid NSAIDs and IM injections.
On to an organ that has always bewildered me... the spleen
