Allergy to Heparins.

Rationale: The Incidence of reactions to heparins may be higher than previously thought.  Extensive cross-reactivity among unfractionated heparin and low molecular weight heparins (LMWH) has been described.

Aim:   To characterize the patients with hypersensitivity to Heparins and the cross-reactivity among heparins in our clinical practice.

Methods: Retrospective study was performed in our Allergy Unit from 2013-2015. Clinical data were registered from all patients who developed heparins hypersensitivity. Skin/challenge test were performed with the heparin involved and with others LMWH.

Results: From a total of 20 patients, 10 were finally diagnosed of allergy to at least one heparin. Mean age: 61,25y.o. From these, 37.5% had other drug allergies (NSAID, Contrast agents) and 37.55% were atopic. Nine out of 10 cases developed cutaneous symptoms and one anaphylaxis.

 Patch test with the suspected drug was positive in one case to Bemiparin and Enoxaparin. Prick/ID were performed in all patients, with one positive result in delayed reading.

 Positive Subcutaneous challenge were: Enoxaparin in 40%, Bemiparin in 10%, Enoxaparin and Bemiparin i30%, Enoxaparin, Bemiparin, Nadroparin, Tinzaparin and Heparin in 10% and Heparin in10%.

 Intravenous provocation with heparin was not performed because of the severity of the episodes developed by the patient (4 anaphylaxis)

Conclusions:

- In this study the frequency of heparin allergy is low but increasing, being the most common type of reaction delayed-type hypersensitivity (DTH). 

- We observed a high cross-reactivity among LMWHs and Heparin.

- Challenge is considered the gold standard for the diagnose, being the clinical findings similar to previous reported.