27 Nov 2020

10/22/20: Myasthenia Gravis 2/2 Thymoma

PGY3 Sheila Kapyur presented a case of a 37 year old female with recent diagnosis of asthma who came with the complaint of worsening cough.  Patient stated that she was diagnosed with asthma 2 months ago.  She is now coming with worsening dyspnea on exertion, palpitations, and cough productive of yellow sputum for one month as well as two days nocturnal dyspnea and orthopnea and subjective fevers for one day.  Patient was walking down the street in the morning prior to arrival when her dyspnea became too severe; she sat down and called a taxi to take her to the hospital.  She does not have any other medical problems and does not have any home medications.  She denied any tobacco/alcohol/drug use and worked at a desk job, without any exposure to pets, chemicals or factories.

Vitals: T 36, HR 122, RR 28, BP 134/84, O2 sat 100% on 4L NC

Physical Exam significant for tachycardia, poor inspiratory effort, no crackles/wheezes/rhonchi, no peripheral edema and no lymphadenopathy.

CBC: WBC 8.8> Hb 13.3/Hct 41.8 <Plt 460 (MCV 75.1, RDW 16%)

Diff: 70.3% PMN, 23.4% lymph, 5.9% monocytes, 0% eosinophils, and 0.4% basophils

CMP:

Na 139/K 4.1/Cl 101/HCO3 23/BUN 11/Cr 0.62 <Glucose 91

ALP 64>T.protein 7/Albumin 4.2/AST 48/ALT 39/Tbili <0.2

Coags: PT 12.7, INR 0.96, PTT 32

CXR had few patchy opacities seen in the RLL.

2 hours into the ED visit, the patient was noted to become more drowsy with decreased respiratory effort thought she remained able to follow commands.

A stat ABG showed: 7.1/86/358/27 on 21% FiO2.  Ddimer was elevated at 411 (normal 0-249).

Stat CTPA performed did not show any pulmonary embolism but showed a predominately soft tissue attenuation anterior mediastinal mass measuring 5.6 x 3.4cm with a smaller cystic area along the inferomedial aspect.

Infectious workup was negative.  Malignancy workup with tumor markers also negative. 

Neurology was consulted and recommended sending acetylcholine receptor antibodies which was elevated upon result. 

CT guided biopsy of the mediastinal mass was done which showed thymoma.

Treatment: Patient was intubated on admission due to acute hypercapneic respiratory failure. She was started on Pyridostigmine for high suspicion of myasthenia gravis while pending biopsy results. Patient continued to fail extubation parameters and eventually underwent tracheostomy. Given minimal improvement on pyridostigmine, she was started on plasmapheresis and later IV steroids and IVIg. She received a thymectomy later in the course of her hospitalization and was able to be weaned to trach collar and discharged to acute rehabilitation facility.

Teaching points:

  1. Thymomas account for 50% of anterior mediastinal mass (4 T’s – Teratoma, Thymoma, Terrible Lymphoma, Thyroid).
  2. 70% thymomas are associated with paraneoplastic syndromes with the most common being myasthenia gravis.
  3. Diagnosis: Ice pack test/edrophonium OR serologic antibody testing OR repetitive nerve stimulation OR single fiber EMG (most sensitive)
  4. Treatment: Pyridostigmine, chronic immunotherapies, plasmapheresis, IVIg, Thymectomy
  5. Medications that worsen MG: macrolides, beta blockers, CCB

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