HISTORY: A 14-year-old male soccer player presented with bilateral lower leg pain and weakness. Ten days prior, he was at a lake cottage in Indiana, where he had an acute onset of bilateral leg pain, fatigue, and headache. He had a difficult time walking with a wide-based gait. Family attributed the symptoms to fatigue from intensive soccer conditioning. Over the next few days, leg pain and weakness improved, but, at soccer, he had a difficult time running and increased leg pain. He denied fevers, chills, neck pain, nausea, vomiting, diarrhea, rash, insect bites, bowel or bladder dysfunction, or upper extremity weakness. He had recent exposure to lake water, but no family members with similar symptoms. Family history was negative for neurologic, cardiac, or rheumatologic disease. PHYSICAL EXAMINATION: Well-appearing child with normal vital signs. Difficulty getting off the examination table with antalgic, wide-based gait. Diminished 4/5 strength of the bilateral proximal quadriceps, but otherwise with normal strength of the upper and lower body. Tender to palpation of the bilateral calf and quadriceps muscles without muscle or joint swelling. Neurological exam with normal deep tendon reflexes (DTRs), negative clonus, and negative Babinski. Skin without lesions. DIFFERENTIAL DIAGNOSIS: 1. Viral myositis 2. Inflammatory myopathy 3. Guillain-barré syndrome 4. Neuroparasitic infection 5. Muscular dystrophy 6. Rhabdomyolysis TEST AND RESULTS: Labs: CK 486 U/L at presentation, decreased to 66 U/L. CBC, electrolytes, TSH, ESR, CRP, urinalysis, myoglobin, CSF, ANA, and Lyme serology all normal. Imaging: Spine MRI with prominent ventral nerve root enhancement of the caudal equina (a common finding seen in Guillain-barré syndrome although not specific). EMG: Motor nerve conduction with significant reduction in compound muscle action potential amplitude. FINAL/WORKING DIAGNOSIS: Guillain-barré syndrome (GBS) with likely subacute/acute motor axonal neuropathy TREATMENT & OUTCOMES: 1. Referred to neuromuscular disorders clinic with progressive loss of DTRs. 2. Admitted to the hospital following EMG suggestive of GBS and received intravenous immunoglobulin. 3. Discharged on 60 mg of oral prednisone daily with the plan to taper. 4. Currently in weekly physical therapy with complete resolution of pain and weakness.