Heparin-Induced Thrombocytopenia during Plasmaphoresis in a Patient with Neuromyelitis Optica

Background: Heparin-induced thrombocytopenia (HIT) is a dangerous and potentially lethal condition that causes thrombocytopenia with or without thrombosis. It is caused by an immune reaction where IgG antibodies are formed against the platelet factor 4/heparin complex bind to the platelet surface and causing activation that leads to decreased platelets and/or thrombosis. Neuromyelitis optica (NMO) is an autoimmune demyelinating disorder with autoantibodies against aquaporin 4, causing attacks of optic neuritis, longitudinally extensive transverse myelitis (LETM), and area postrema syndrome (APS). Plasmaphoresis (PLEX) has been used for the treatment of acute attacks in NMO. 

Objectives: We report a case of HIT during PLEX treatment in a patient with LETM from NMO.

Methods: Not applicable

Results: 50-year-old Hispanic female with suspected NMO presented to the hospital with paraplegia and numbness with a T6 sensory level, urinary retention, and intractable nausea and vomiting. She had 3 prior episodes of LETM over the last 6 months, one was associated with intractable hiccups concerning for APS. NMO antibody testing by ELISA was negative 3 times. She was admitted for suspicion of recurrent LETM and APS. MRI brain showed no new or enhancing lesions. MRI cervical spine showed improvement of C7 T2 hyperintense lesion. MRI thoracic spine showed a confluent T2 hyperintense lesion from T3-T9 with post contrast enhancement from T6-T8 as well as focal enhancing lesions at T4 and T5. She was started on intravenous methylprednisolone and PLEX therapy. Repeat NMO antibody by florescence activated cell sorting assay came back positive. On admission platelets where 223K/mcl, and on hospital day 6 had dropped to 116K/mcl.  Platelet nadir was on hospital day 7 at 109K/mcl. HIT was suspected and enoxaparin sodium prophylaxis was discontinued as well as heparin flushes to maintain her dialysis catheter and she was placed on foundaparinux for prophylaxis and alteplase was used for her dialysis catheter. HIT IgG antibodies to platelet factor 4 and serotonin release assay were both positive. Platelets stabilized and returned to normal.

This is the fifth case known to us with HIT in the setting of demyelinating disease, and the third with NMO, during PLEX treatment. Two of the cases were with minimal heparin exposure through the catheters, and a higher risk of HIT among patients with B cell driven chronic inflammatory conditions was proposed. We successfully maintained her dialysis catheter with alteplase, two of the cases uses saline flushes and the other two used citrate-based anticoagulant successfully.

Conclusions: We recommend clinicians should have a high index of suspicion of HIT in patients on any form of heparin. We also recommend close monitoring of patients with demyelinating disorders treated with PLEX for the possibility of HIT. It is important to remember the impact of heparin packing of the dialysis catheters as well.