IVIG Therapy for Myositis with Severe Proximal Muscle Weakness

Patient Clinical Presentation

A patient with a 1-year history of progressive proximal muscle weakness, with 3 months of acute worsening, has demonstrated significant functional limitations affecting daily activities, including inability to rise from a seated position without using arms and difficulty with self-care activities, and has been diagnosed with Grade 3 myositis, characterized by hip flexion 3/5 bilaterally, and laboratory findings of elevated muscle enzymes and inflammatory markers 1
The patient has a history of progressive proximal muscle weakness, with significant functional limitations, including difficulty with brushing teeth and combing hair, and has been found to have positive HMGCR antibodies and elevated inflammatory markers, indicating an immune-mediated necrotizing myopathy 2
The patient's laboratory findings include elevated muscle enzymes and inflammatory markers, such as CK and ESR, and CRP, which are indicative of an inflammatory myopathy 1
The patient has previously been treated with high-dose corticosteroids, but has not adequately responded to this treatment, and therefore meets the criteria for IVIG therapy 2

According to the American Society of Clinical Oncology (ASCO) guidelines, IVIG therapy is indicated for patients with Grade 3-4 myositis who have an inadequate response to corticosteroids, which is characterized by severe weakness limiting self-care activities, and the patient meets these criteria 2, 3
The patient's severe weakness, positive HMGCR antibodies, elevated inflammatory markers, and inadequate response to corticosteroids meet the criteria for IVIG therapy, as recommended by the ASCO guidelines 2, 3

The first-line therapy for severe myositis is high-dose corticosteroids, which the patient has already received, but for patients with an inadequate response to steroids, IVIG therapy should be considered, as recommended by the Mayo Clinic Proceedings 4
For patients with Grade 3-4 weakness who have not responded to corticosteroids, IVIG therapy should be added, and the patient should be considered for hospitalization and urgent referral to a rheumatologist or neurologist, as recommended by the ASCO guidelines 2, 3

IVIG should not be administered immediately before plasmapheresis, as it will be removed, and careful monitoring of response is needed, with consideration of additional immunosuppressive therapy if symptoms worsen or do not improve after 2-4 weeks, as recommended by the ASCO guidelines 2, 3
If symptoms and muscle enzyme levels do not resolve after 4 weeks, consideration should be given to adding other immunosuppressants, such as methotrexate, azathioprine, or mycophenolate mofetil, as recommended by the ASCO guidelines 2, 5
For maintenance therapy after initial response, consideration should be given to transitioning to steroid-sparing agents, as recommended by the Mayo Clinic Proceedings 4

The patient has been diagnosed with autoimmune necrotizing myopathy, a type of inflammatory myopathy characterized by muscle weakness and elevated muscle enzymes, indicating ongoing muscle inflammation despite previous treatment, supporting the medical necessity of IVIG therapy 6, 7, 8

The standard dosing for IVIG in inflammatory myopathies is 1-2 g/kg of ideal body weight, usually given over 2 consecutive days (1 g/kg each day) once a month for 1-6 months 9
The patient is receiving 50g of Gammagard Liquid (10%) which is appropriate based on weight-based dosing 9

Hydrocortisone sodium succinate (Solu-CORTEF) 100 mg is appropriate as pre-medication to prevent infusion reactions 9
Diphenhydramine (Benadryl) 25 mg is appropriate as pre-medication to prevent allergic reactions to IVIG 9
The combination of these medications with IVIG represents standard practice for infusion protocols 9

Failure to check IgA levels before administering IVIG can lead to severe anaphylactic reactions in IgA-deficient patients 9