PC2155: Trade Ya: An Interesting Twist on Eating Disorder Diagnosis Swapped for Myasthenia Gravis

Introduction: While avoiding and restricting oral intake are classic symptoms of Avoidant/Restrictive Food Intake Disorder (ARFID), these behaviors may also be caused by systemic diseases. Myasthenia Gravis (MG) is a neuromuscular disorder causing fluctuating weakness involving combinations of ocular, bulbar, respiratory, and limb muscles which may lead to disruptions in eating.

Case Description: A 12-year-old female with ARFID, asthma, anxiety/depression, and nasogastric tube (NGT) dependence was admitted for acute weight loss secondary to failed outpatient management of her eating disorder. Her eating difficulties began after scoliosis surgery one year prior, also around the time of her father’s deportation. Symptoms included eating slowly, difficulty swallowing, and choking episodes leading to fear of eating. She had normal growth and development until that time. On admission, she was normotensive, mildly tachycardic, with otherwise normal vitals. Her admission weight was 87 pounds; BMI of 17.06 kg/m² (10th percentile). Exam revealed a thin habitus, limited neck ROM due scoliosis, tachycardia (attributed to dehydration), and a high-pitched, nasal voice. Admission labs, including complete blood count, comprehensive metabolic panel, magnesium, phosphorus, and thyroid studies were all normal. She was reinitiated on NGT feeds, and about twelve hours later, she became hypoxic with shallow breathing. She remained afebrile with clear lungs sounds; chest X-ray showed low lung volumes and appropriate NGT placement. She improved on albuterol and supplementation oxygen. EKG and ECHO ordered to exclude malnutrition-associated cardiac involvement were normal. Twelve hours later, she had another episode of shallow breathing, lethargy, apnea and head dropping episodes. Her venous blood gas showed significant hypercapnia (pCO2 107), with primary respiratory acidosis (pH 7.25) and metabolic compensation (HCO3 48). Toxicology screen was negative. She was transferred to the ICU for BiPAP with resultant improvement in her mental and respiratory status. Additional history obtained was notable for ongoing episodic double vision, drooling, muscle fatigability, and head dropping, as well as notable changes to her voice. A neuromuscular disorder was suspected and was ultimately diagnosed with Muscle-Specific Tyrosine Kinase (MuSk) antibody-positive MG in an acute myasthenia crisis. Since the diagnosis, she has received multiple rounds of IVIG and plasma exchange, and most recently was initiated on weekly rituximab infusions given difficulty in treating Anti-MuSk positive MG with just pyridostigmine [1]. Since being on treatment for 8 months, her BMI increased to the 56th percentile (weighing 103 lbs).

Discussion: Providers should evaluate for psychological disorders as a cause of eating difficulties and malnutrition, but it is essential to keep neuromuscular disorders in mind when presented with concurrent bulbar symptoms and other signs of fatigability. Early recognition and treatment can prevent myasthenic crises and mitigate failure to thrive.

Conclusion: It is now thought that her ARFID symptoms were manifestations of MG rather than an eating disorder.