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Título

Myopathy miss diagnosed as Amyotrophic Lateral Sclerosis for seven years - Diagnostic challenges of neuromuscular disease

RESUMO

Case report: Male, 56 years old, was referred to EMG lab by a rheumatologist for evaluation of his Amyotrophic Lateral Sclerosis (ALS). He arrived with complaints of weakness and sadness because he received a diagnostic seven years ago. Since the diagnostic, he was expecting his physical decline, as said by his attendant. It slowly evolves. That moment was the first time some doctor asked him to repeat the electromyography (EMG) test after the first two diagnostic tests. Physical exam: Medical research council (MRC) strength in the triceps and the quadriceps was IV, He had prominent atrophy of facial, arms and legs muscles. Sensory examination was markedly normal. The two previous EMG reports demonstrated prominent fibrillations (Fibs) and positive sharp waves (PSWs) with increased motor unit potentials (MUPs) and with a final statement of motor neuron disease. We performed a new EMG that showed Fibs and PSWs. Interesting that was no high amplitude MUP, instead, we are able, with quantitative EMG, to show a great number of small amplitude and short duration (SASD) MUPs, consistent with active myopathy. Muscle biopsy show inflammatory infiltrate. Corticosteroids were started and the patient slowly evolves with significant recovery of symptoms. Discussion: The ALS diagnostic is a dramatic report to be given to any patient. The findings of widespread active denervation and chronic reinnervation in three different corporal segments were easily obtained in this case. The normal sensory examination also corroborates for the establishment of the diagnosis of ALS. High amplitude and long duration MUPs also were there. The patient stayed waiting for his slow decline and it was a surprise when he shows up with seven years of ALS history walking with some difficulty but without any assistive device and speaking normally. To us, it was an easy diagnostic as the patient still has widespread positive sharp waves with fibrillation potentials, small amplitude short duration MUPs and no HALD MUPs. Many reasons can throw us in the wrong diagnostic direction in this case. In Brazil, in our lab, we see too many HALD without reasonable explanation in a way that we don't have seen in the USA. As in this case, the true cause of weakness was hidden under HALD MUPs. Final comments: We encourage the routine use of quantitative EMG techniques to discover and quantify the SASD that otherwise can pass masked as seen in this case.