[A case of spinal muscular atrophy type 0 in Japan]

The patient was a 2-month-old female infant born at 41 weeks and 2 days of gestation presenting multiple arthrogryposis, severe muscle hypotonia and respiratory distress with difficulty in feeding. She suffered from repeated complications with aspiration pneumonia. On admission to our hospital, she exhibited fasciculation and absence of deep tendon reflexes. Examination of the motor nerve conduction velocity (MCV) revealed no muscle contraction. Deletions of the SMN and NAIP genes were noted. Based on severe clinical course and disease development in utero, she was given a diagnosis of spinal muscular atrophy (SMA) type 0 (very severe type). Arthrogryposis and disappearance of MCV are exclusion criteria for SMA. However, the clinical course of the infant was very severe and included such exclusion items. Consequently, when an infant presents muscle hypotonia and respiratory distress, SMA must be considered as one of the differential diagnoses, even though arthrogryposis is an exclusion criterion for SMA. We discuss this case in relation to the few extant reports on SMA type 0 in Japanese infants in the literature.