Mucous membrane pemphigoid, thymoma, and myasthenia gravis
Authors: Sabet Haideh Yazdani ,   BA, Davis Jaime L. , Rogers Roy S. 
Published: January 2009

In November 1997, approximately 1 year before being evaluated at the Mayo Clinic, Rochester, a 63‐year‐old woman presented with erosive tongue lesions that were diagnosed by her physician as oral lichen planus. The lesions responded well to 3 months of treatment with systemic and topical corticosteroids and topical antiyeast medication. She stopped taking the medications and had a relapse. A few months after the oral lesions developed, her left eyelid became ptotic. Results of magnetic resonance imaging of her brain were normal, and the ptosis resolved spontaneously after 2 weeks. One year later, her right eyelid began to droop, and the results of edrophonium testing were positive. She was prescribed prednisone, 30 mg daily, and pyridostigmine, as needed. The ptosis improved, but never fully resolved. Radiography revealed a left ‘‘thyroid nodule,’' but computed tomography did not show a mediastinal mass. She was advised to have the ‘‘nodule’' removed surgically and came to the Mayo Clinic, Rochester, for a second opinion.

Her medical history was significant for the following: tinnitus, glaucoma, early bilateral cataracts, and long‐standing hypertension, for which she took losartan, 50 mg twice daily. Other medications included: prednisone, 30 mg daily; pyridostigmine as needed; famotidine, 40 mg daily; and eyedrops for glaucoma. She denied any history of hyperthyroidism or hypothyroidism, head and neck irradiation, family history of thyroid disease, or diplopia. Hepatitis serologic studies revealed hepatitis B exposure and recovery, hepatitis C immunity, and a previous hepatitis A viral infection.

On examination at the Mayo Clinic, Rochester, an erosive hypertrophic plaque was noted on the posterior dorsal half of the tongue, and vesicles and erythematous erosions on the hard and soft palates ( Fig. 1a). A lace‐like white pattern was seen on the buccal mucosa bilaterally, and a small erosive patch on the left buccal mucosa (
Fig. 1b). Ocular and nasal mucous membranes were normal in appearance, and there were no pertinent skin findings. Dermatopathologic examination of an excisional biopsy specimen from the left dorsum of the tongue demonstrated an ulcer with epitheliomatous hyperplasia and a granulomatous reaction, presumably due to yeast infection. Silver staining showed hyphae and yeast at the base of the tongue ulcer. The results of the direct immunofluorescence study were negative and revealed no lichenoid changes on hematoxylin and eosin staining. Indirect immunofluorescence testing of the serum revealed a 1 : 80 titer of basement membrane zone antibodies, reflecting pemphigoid. This test was positive on repeat study. Salt‐split skin on monkey esophagus revealed an epidermal pattern of basement membrane zone antibodies. Treatment included fluocinonide gel applied to the involved areas four times daily and oral antiyeast therapy (fluconazole, 200 mg once daily by mouth) while the rest of the evaluation was being completed.

Erosive hypertrophic tongue plaque.

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Erosive patch on the buccal mucosa.

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As part of the evaluation of the ptosis, a myasthenia gravis antibody panel was performed. It revealed the following abnormalities: striated muscle antibody at 1 : 480 (reference range, <1 : 60), acetylcholine receptor binding antibody at 6.33 nmol/L (reference range, ≤ 0.02 nmol/L), acetylcholine receptor blocking antibody at 31% (reference range, 0–25%), and acetylcholine receptor modulating antibody at 100% (reference range, 0–20%), suggesting thymoma. Treatment included pyridostigmine, 30–45 mg 3–4 times daily, to control the myasthenia symptoms, while the ill‐defined neck mass was being evaluated.

A mildly enlarged thyroid was noted on physical examination. Hematology panel revealed thyroid‐stimulating hormone (TSH) levels in the low normal range; the thyroid microsomal antibody was normal. Chest radiography showed minor tracheal deviation, and a previous computed tomogram showed what appeared to be a 3‐cm enlarged mass in the thyroid. Ultrasonographically guided thyroid biopsy did not show malignancy, but a benign mesenchymal‐type tumor was found and surgical excision was planned. Intraoperatively, a thymoma of the left cervical thymic tongue was found.

At 6 months' follow‐up, the ptosis and oral mucosal lesions had improved significantly, although she continued topical corticosteroid therapy intermittently for minor erosive oral disease.