However, those who have been exposed to heparin in the last few months may still have circulating IgG, as IgG-type antibodies generally continue to be produced even when their precipitant has been removed. This is similar to immunity against certain microorganisms, with the difference that the HIT antibody does not persist more than three months. HIT antibodies have been found in individuals with thrombocytopenia and thrombosis who had no prior exposure to heparin, but the majority are found in people who are receiving heparin.The IgG antibodies form a complex with heparin and PF4 in the bloodstream. The tail of the antibody then binds to the FcγIIa receptor, a protein on the surface of the platelet. This results in platelet activation and the formation of platelet microparticles, which initiate the formation of blood clots; the platelet count falls as a result, leading to thrombocytopenia. In addition, the reticuloendothelial system (mostly the spleen) removes the antibody-coated platelets, further contributing to the thrombocytopenia. Formation of PF4-heparin antibodies is common in people receiving heparin, but only a proportion of these develop thrombocytopenia or thrombosis. This has been referred to as an "iceberg phenomenon". Diagnosis
HIT may be suspected if blood tests show a falling platelet count in someone receiving heparin, even if the heparin has already been discontinued. Professional guidelines recommend that people receiving heparin have a complete blood count (which includes a platelet count) on a regular basis while receiving heparin.However, not all people with a falling platelet count while receiving heparin turn out to have HIT.
Erbs palsy  is a paralysis of the arm caused by injury to the upper group of the arms main nerves, specifically the severing of the upper trunk C5–C6 nerves. These form part of the brachial plexus, comprising the ventral rami of spinal nerves C5–C8 and thoracic nerve T1. These injuries arise most commonly, but not exclusively, from shoulder dystocia during a difficult birth. Depending on the nature of the damage, the paralysis can either resolve on its own over a period of months, necessitate rehabilitative therapy, or require surgery. Presentation
The paralysis can be partial or complete; the damage to each nerve can range from bruising to tearing. The most commonly involved root is C5 (aka Erbs point: the union of C5 & C6 roots) as this is mechanically the furthest point from the force of traction, therefore, the first/most affected. Erb–Duchenne palsy presents as a lower motor neuron syndrome associated with sensibility disturbance and vegetative phenomena.The most commonly involved nerves are the suprascapular nerve, musculocutaneous nerve, and the axillary nerve.The signs of Erbs palsy include loss of sensation in the arm and paralysis and atrophy of the deltoid, biceps, and brachialis muscles. "The position of the limb, under such conditions, is characteristic: the arm hangs by the side and is rotated medially; the forearm is extended and pronated. The arm cannot be raised from the side; all power of flexion of the elbow is lost, as is also supination of the forearm".