[A case of isolated ACTH deficiency with neuromuscular symptoms]

A female case of isolated ACTH deficiency associated with neuromuscular symptoms was reported. Although her initial development was delayed with perinatal troubles, developmental catch up was seen. The patient complained of general fatigue with weakness and poor school performance at the age of eleven. Muscle weakness predominant to the proximal portion and mental dullness were suspected from neurological examination. Her laboratory data were as follows; mild elevation of CK in serum, subclinical thyroidal dysfunction, abnormal electrocardiogram, slow wave activity on electroencephalogram, delayed nerve conduction velocity, and localized hypoperfusion of cerebral blood flow on single photon emission computed tomogram. Histological examination of muscle biopsy demonstrated only mild fiber size variation. During two years' follow-up, her intelligence quotient fell down, while muscle weakness did not progress significantly. At the age of fourteen, a low level of plasma ACTH was pointed out by chance and a definitive diagnosis was obtained by endocrinological examinations; no response of ACTH and cortisol on insulin stimulation, delayed response of cortisol on continuous ACTH stimulation, and no response of plasma ACTH on corticotropin releasing hormone stimulation. Other signs of adrenocortical insufficiency, such as hypoglycemia and abnormal serum electrolytes, were not observed during the clinical course. This case suggested that isolated ACTH deficiency should be considered for differential diagnosis of neuromuscular disorders.