Giant cell myositis responsive to combined corticosteroids and immunoglobulin

Abstract

A 70-year-old man presented with respiratory distress and proximal muscle weakness shortly after biopsy of a left forearm mass. The biopsy showed giant cell myositis, and serological investigations identified a grossly elevated serum creatine kinase level, suggesting skeletal muscle damage. Serum troponin T was also high, but troponin I was normal. Serum antiacetylcholine receptor antibodies were positive, and imaging showed a thymoma. He recovered well following intravenous immunoglobulin and corticosteroids, and later underwent thymectomy. He is currently in sustained remission, with no clinically detectable myasthenia, but subsequently, developed hypogammaglobulinaemia. Neurologists should remember giant cell myositis/myocarditis can occur in patients who have myasthenia gravis with thymoma, as it is potentially fatal, but may respond to immunosuppression.

Inflammatory myopathy with myasthenia gravis

“…In addition to PM pattern pathology, massive collections of CD20 + B-lymphocytes were observed in 2 patients and CD68 + granulomas in 1 patient. These pathologic findings have already been reported in patients with both idiopathic IM and MG. 3,9–11,13,28 Because the thymus gland is a central lymphatic organ that provides various immunologic functions, multifactorial autoimmune dysregulation in thymic disorders, including thymoma, has been reported. 36 Further studies are needed to elucidate the overall immune mechanisms that cause these complicated pathologic features.…”

“…Myasthenia gravis (MG) is rarely associated with IM. The reported clinical features of patients with both idiopathic IM and MG included brachio-cervical weakness or dropped head, 1–5 respiratory decompensation, 3–10 muscle swelling with pain, 4,11 cardiac involvement, 4,5,9 and markedly elevated serum creatine kinase (CK) levels. 4,6,8 In addition, patients with anti–acetylcholine receptor (anti-AChR) antibody (Ab)-positive thymomatous IM without MG symptoms showing rapidly progressive weakness and respiratory failure with markedly elevated serum CK levels 12,13 have been described.…”

Giant cell myositis associated with metastatic thymoma and granulomatous hypercalcaemia

“…Regarding the patient’s concomitant metastatic thymoma, although an association between thymoma and GCM has been previously described,2 few reports have included thymoma staging and pathological subtypes 3 15–18. Metastatic thymoma is relatively rare, as only approximately 12% of thymic tumours have been found to invade distant structures,19 20 most commonly pleura or pericardium 21.…”

Granulomatous myopathy: Sarcoidosis and beyond

“…Inflammatory myopathies have been reported in about 0.9% to 1% of immune checkpoint inhibitor‐naive myasthenia gravis patients 46,47 . Muscle biopsies typically show endomysial cytotoxic T cells surrounding and sometimes invading non‐necrotic muscle fibers 47 ; however, granulomatous inflammation in muscle has been described in some case reports and series 48–63 . Myasthenia gravis patients with granulomatous myopathy and those with non‐granulomatous inflammatory myopathy share several common clinical features.…”

“…46,47 Muscle biopsies typically show endomysial cytotoxic T cells surrounding and sometimes invading non-necrotic muscle fibers 47 ; however, granulomatous inflammation in muscle has been described in some case reports and series. [48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63] Myasthenia gravis patients with granulomatous myopathy and those with non-granulomatous inflammatory myopathy share several common clinical features. The age of onset is mainly in the sixth to seventh decades, with a female predominance.…”