Subcutaneous immunotherapy (SCIT) aims to achieve clinical tolerance for allergens. Systemic reactions to SCIT are classified into 4 grades. Uterine cramps fall under grade 2, and are rare. Literature review revealed only 3 case reports since 1997, 2 of them related to venom SCIT.
Four cases of endometrial anaphylaxis due to SCIT with environmental allergens were identified via retrospective case review of electronic medical record at allergy clinic of a tertiary referral medical center between 2010 to 2014.
Endometrial anaphylaxis was observed during buildup phase of SCIT in two patients and during maintenance therapy the other two. Symptoms occurred 30-45 minutes after SCIT injections. In all cases, immediate hypersensitivity reactions without uterine cramps had been reported with previous SCIT injections. Two patients had recurrent episodes of uterine cramps even after adjusting schedule and dose of SCIT. Premedication with antihistamine and montelukast did not affect the reactions. Uterine cramps lasted for approximately one hour after the administration of epinephrine and diphenhydramine. Severe uterine cramp-like pain was the sole manifestation in one patient, whereas the others had associated urticaria, angioedema or diffuse erythema/flushing. None of the patients had a history of dysmenorrhea prior to SCIT. No vaginal bleeding was reported during uterine cramps.
Endometrial anaphylaxis is one of the rare adverse reactions to SCIT which may be underrecognized and underreported. This is the largest reported case series at this time. Increased awareness should facilitate more research in this rare but significant adverse reaction to SCIT.