Repository Corticotropin Injection (Acthar Gel) Resolving Recurrent Idiopathic Orbital Myositis: A Case Report

Introduction: A 64-year-old male was referred to clinic with a chief complaint of OD irritation and right lower lid fullness. His past medical history and family history were nonsignificant.

Case: A CT scan revealed an inflamed right medial rectus muscle ([Fig. 1]) that, along with an exophthalmometer reading indicating a 2-mm asymmetrical OD protrusion, yielded an IOM diagnosis. The patient’s symptoms initially resolved through completing a prednisone treatment course of thrice daily oral 20-mg tablet for 1 week, then twice daily for 2 weeks, then once daily for 2 weeks. However, IOM symptoms recurred 2 months after initial resolution.

Fig. 1 CT scan displaying patient’s enlarged right medial rectus muscle.

The patient opted out of resuming prednisone treatment and rejected a biopsy; therefore the patient started empiric Acthar Gel treatment beginning with 40 mg twice weekly. At both follow-up visits 1 and 4 months after starting treatment, the patient reported symptomatic improvement but also gradually increasing blood pressure. Thus, at his 4-month follow-up, the patient started taking 50 mg oral metoprolol daily. At his 5-month follow-up, the patient reported normal vitals, no pain, and improvement in quality of life, thus tapering his treatment frequency to once a week.

Discussion: No literature specifically assesses Acthar Gel’s effectiveness in treating IOM as a recourse after corticosteroid therapy has failed. However, many studies have evaluated its general efficacy as an alternative to corticosteroid therapy, which is a first-line treatment for many other autoimmune and/or inflammatory conditions. Results from multiple studies, some even specific to ophthalmology, report Acthar Gel’s efficacy in treating inflammation while also noting its lesser frequency of adverse effects.

The pharmacologic effects of Acthar Gel are well-documented; it acts on various adrenal glands’ melanocortin receptors to stimulate anti-inflammatory functions such as natural corticosteroid production. However, there is no evidence explaining how Acthar Gel can achieve therapeutic effects in cases where corticosteroid therapies fail, nor the cause of Acthar Gel’s reduced toxicity as reported in literature.

Although this patient experienced a hypertensive episode as a result of using Acthar Gel that subsequently resolved, this case does not necessarily suggest Acthar Gel’s toxicity is comparable to corticosteroids when treating IOM. Rather, more data is needed to evaluate the epidemiological implications of treating IOM with Acthar Gel, given the promising mitigation of symptoms achieved in this case.

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Artikel online veröffentlicht:
05. Februar 2024