ID 230 – Adult onset acid maltase deficiency – EMG aids diagnosis in Intensive Care Unit

Abstract

A 25 year old man was admitted to Intensive Care Unit with the clinical problems of worsening shortness of breath and a history of progressive proximal limb weakness and bilateral ptosis. He was found to have marked type II respiratory failure and significant proximal weakness both the upper and lower limbs and also marked extra-ocular muscle weakness. Arterial Blood Gas Analysis was consistent with type II respiratory failure. Muscle enzymes – CK levels were elevated -1174 U. Acetyl Choline Receptor antibodies – Negative. Neurophysiological Studies – Normal nerve conduction studies; EMG evaluation demonstrated marked myopathic abnormalities in proximal and distal muscles in lower as well as upper limbs. Some muscles showed frequent pseudo-myotonic discharges. The clinical presentation of progressive muscle weakness and Type II respiratory failure along with EMG features raised the possibility of adult onset Acid Maltase deficiency. Muscle biopsy demonstrated accumulation of glycogen within membrane bound vacuoles consistent with adult onset Acid Maltase Deficiency (Pompe’s disease of adult onset). Awareness of clinical and neurophysiological features of Acid Maltase Deficiency aid the diagnosis of this disorder, particularly in the context of evaluation of respiratory failure cases in an Intensive Care Unit.