MG Complicated by Thymus Tumor and Immunodeficiency Should be Treated with Caution, Case Report Warns

A rare case of myasthenia gravis (MG) complicated by a tumor in the thymus and an immunodeficiency known as Good syndrome has been documented by researchers, who warn against heavy use of certain immunosuppressants that are likely ineffective and pose a risk for serious infections.

The combination of the three conditions had not been previously reported, according to the researchers.

For such cases, they recommend treatment with regular intravenous immunoglobulin (IVIg) plus low-dose immunosuppressants, combined with anticholinesterases such as Mestinon (pyridostigmine), in addition to removal of the thymus gland (thymectomy).

The study, “Thymoma complicated with myasthenia gravis and Good syndrome – a therapeutic conundrum: a case report,” was published in the Journal of Medical Case Reports.

The case report described a 27-year-old man from Sri Lanka who complained of persistent cough and wheezing, associated with a two-year history of chest pain. A chest X-ray found several lesions on the left side lateral wall of his chest.

A computed tomography scan and a biopsy confirmed these lesions to be caused by a tumor of the thymus, known as a thymoma. Of note, about 30%–50% of patients with thymomas develop MG.

While awaiting surgery to remove the thymus and an associated tumor, he began experiencing double vision and eyelid drooping, which is associated with paralysis of a muscle responsible for controlling eye movements (abducens nerve), and also consistent with ocular MG.

Further tests showed problems in the transmission of nerve impulses to muscles and the presence of high blood levels of autoantibodies targeted against the acetylcholine receptor, two hallmarks of MG. This confirmed the clinical diagnosis of MG.

Before starting on immunosuppressive treatment for MG and undergoing thymectomy, the man developed a fever and worse breathing difficulties and cough. He was eventually diagnosed with pneumonia. This precipitated a myasthenic crisis, a sudden and severe worsening of muscle weakness resulting in respiratory failure, which required him to be moved to the intensive care unit (ICU).

He was given a broad-spectrum antibiotic (meropenem) and Mestinon (oral pyridostigmine, also available as generics). Later, the patient was started on plasma exchange, or plasmapheresis, and oral prednisolone (a corticosteroid). Subsequently, he was given IVIg injections for five days.

He did not require intubation or mechanical ventilation, which are commonly required during a myasthenic crisis.

At the ICU, the patient was found to have a combined deficiency in two important types of immune cells, B- and T-cells, confirming a diagnosis of Good syndrome — a rare condition in which thymoma is associated with immunodeficiency, making people more prone to bacterial, viral, and fungal infections, as well as autoimmune diseases.

After completing IVIg therapy, the patient underwent thymectomy and debulking (partial removal) of tumor lesions. He then maintained regular IVIg treatments, plus low-dose oral prednisolone and Mestinon.

“Postoperatively, he made a good recovery without any episodes of acute weakness or the development of infections,” the researchers wrote.

Although thymomas are common among patients with MG, the association with Good syndrome is rare, with 0.2% to 6% of thymomas linked to the syndrome.

This case calls attention to the therapeutic dilemma of using immunosuppressives in an already immunodeficient patient with a rare combination of diseases, MG and Good syndrome, the researchers said.

“From our experience with this patient, we think that in a patient who has undergone thymectomy for refractory MG and Good syndrome, regular intravenous immunoglobulin replacement, in addition to minimum orally administered immunosuppressants combined with anticholinesterases is an appropriate option,” the researchers wrote.

They also recommended that, in patients with B-cell deficiency, agents such as rituximab may not be effective, and high-dose immunosuppressants such as cyclophosphamide may pose “a heightened risk of serious infections and are best avoided.”