S. Chatfield

McArdle Disease Misdiagnosed as Meningitis

Patient: Female, 44 Final Diagnosis: McArdle disease Symptoms: Exercise intolerance • muscle contracture • myalgia • myoglobinuria • recurrent rhabdomyolysis Medication: — Clinical Procedure: — Specialty: Neurology Objective: Rare disease Background: McArdle disease is a glycogen storage disorder mainly characterized by exercise intolerance. Prolonged muscle contracture is also a feature of this condition and may lead to rhabdomyolysis (RM), which is a serious event characterized by acute skeletal muscle damage. Case Report: A 44-year-old female patient presented with an acute contracture of the posterior neck muscles, causing severe nuchal rigidity. The contracture was induced during a dental extraction as she held her mouth open for a prolonged period, with her neck in a rigid position. She presented with severe pain in her ear and head, as well as fever, vomiting, and confusion. Based on her symptoms, she was initially misdiagnosed with bacterial meningitis and experienced an acute allergic reaction to the systemic penicillin she was subsequently administered. Lumbar puncture results were normal. High serum creatine kinase (CK) levels, recurrent exercise-related muscle symptoms, and a previous history of recurrent myoglobinuria raised the suspicion of an underlying neuromuscular condition. McArdle disease was confirmed by muscle biopsy and a genetic test, which revealed that the patient was homozygous for the R50X mutation in the PYGM gene. Conclusions: This case illustrates that even seemingly innocuous movements, if rapid isotonic or prolonged isometric in nature, can elicit a muscle contracture in McArdle disease patients. Here, we highlight the need for careful management in this patient population even during routine healthcare procedures. The allergic reaction to antibiotics emphasises that misdiagnoses may result in iatrogenic harm.

T.P.26

McArdle disease is a rare condition and often people have had symptoms for many years before the diagnosis is made. There is no specific treatment for the condition but early diagnosis and appropriate management may improve exercise tolerance and prevent acute rhabdomyolysis. Here we present a patient with McArdle disease where an acute episode of neck muscle contracture causing nuchal rigidity was misdiagnosed as meningitis. The patient went onto develop an acute allergic reaction to systemic penicillin with potential life-threatening complications. The patient’s neck contracture was induced by dental extraction during which she was required to hold her mouth open and neck rigid for a prolonged time. This case illustrates that contracture in McArdle disease does not necessarily follow ’exercise’ and highlights the need for careful management during procedures.