Answer

Misdiagnosis of Myasthenia Gravis Presenting with Tongue Thrusting

Pearls

Myasthenia Gravis (MG) is a neuromuscular disorder. Common clinical presentations include ocular symptoms characterized by skeleton muscle weakness in the ocular distributions due to the blocking of the neuromuscular transmission by the antiacetylcholine receptor antibodies. 

Uncommon presentations such as tongue thrusting may also indicate MG complications. Unlike other common signs, tongue thrusting can present diagnostic pitfalls for neurologists and physicians. In patients with tongue thrusting, the possibility of developing MG should never be overlooked.

Despite its rarity, tongue thrusting is frequently associated with MG conditions. It can serve as a barrier to correct MG diagnosis or delayed diagnosis. 

Discussion

MG is an autoimmune disease characterized by various clinical presentations, including bulbar symptoms, respiratory muscle weakness, and ocular fatigability. Although it is widely related to antibody profiles against acetylcholine receptors (AChRs), rare occurrences associated with muscle-specific kinase receptor antibodies and lipoprotein-related protein 4 are evident (Rodolico et al., 2016). The variability in its presentations makes MG one of the most difficult to diagnose conditions. Often, the common symptoms associated with AChRs, that account for about 80% of MG patients (Jordan & Freimer, 2018), may deceive the accessing physicians or neurologists because the weakness presentation can be mistaken for other conditions like age or neurological infections. 

Age, gender, disease onset symptoms, and autoimmune diseases are some of the likely clinical predictors of MG prognosis (Wang et al., 2017). In women, symptom onsets start in the third decades, while in men, it can delay up to the sixth decade of life. The weakness of bulbar muscles is evident in only 60% of MG cases, while it has been reported to be a major complaint in only 15% of the cases (Saini et al., 2017). This explains why MG diagnosis often delay in aged patients as the ocular weakness symptoms often lack at the time of presentation, only to emerge later. Although only 28% of patients develop dysphagia at some point during the disease progression, the involvement of neuromuscular junctions can lead to fatigable dysarthria with tongue weakness and voice alliteration (Marshal et al., 2018). Tongue weakness means the inability to coordinate swallowing and manipulate food bolus.

The cardinal symptoms of MG are fatigue and weakness (Birnbaum et al., 2018). Thus, enduring symptoms like tongue thrusting often seem incompatible with the disease. In one particular case, a 36-year-old female patient diagnosed with MG continued her sporting activities despite being advised to stop as one way of managing her condition (Birnbaum et al., 2018). Even though she experienced bulbar, limb, and ocular fatigability, she continued with her regular exercises. Interestingly, she achieved remarkable disease stability and good health improvement (Birnbaum et al., 2018).

 In a similar case reported by Marshal et al. (2018), the physician initially misdiagnosed the dysarthria and subjective swollen tongue sensation as anaphylaxis. The patient, an elderly man, exhibited uncoordinated swallowing that resulted in leakages into the oesophagus. The delay in MG diagnosis can result in severe implications for patients, particularly the elderly. In cases with severe dysphagia like this, clinicians are always in a dilemma about introducing a gastrostomy tube, something most patients often object (Marshal et al., 2018). The need to avoid such distressing and invasive medical procedures shows the significance of correct and expedient MG diagnosis.