Four infants with neurogenic arthrogryposis who died of respiratory failure before 1 month of age had DNA testing of autopsy specimens for SMN^T gene deletion in a study at the Children’s Hospital of Philadelphia, PA, and the Children’s Hospital at Dartmouth, Lebanon, NH. All infants had clinical, pathologic, or EMG evidence of motor neuron disease. In addition to anterior horn cell loss, autopsies showed a more extensive neurodegeneration involving central sensory neurons in Clarke’s column and the thalamus. SMN^T deletion was identified in two of the cases. [1]

COMMENT. Arthrogryposis in association with infantile spinal muscular atrophy (Werdnig-Hoffmann disease) was first reported by Byers and Banker (1961). DNA analysis for SMN^T deletion in cases of neurogenic arthrogryposis may uncover a diagnosis of spinal muscular atrophy or SMA variant and facilitate genetic counselling. Some cases of infantile SMA may have degenerative changes in sensory neurons in addition to the classical anterior horn cell loss.

Congenital axonal neuropathy with SMN deletion is reported in three newborn siblings presenting with generalized weakness, asphyxia, facial diplegia, and external ophthalmoplegia, and studied at Pediatric University Hospital, Mathildenstr, Freiburg, Germany [2]. EMG, NCV, and nerve biopsies confirmed an axonal neuropathy. The electrophysiological and biopsy findings, together with the SMN gene deletion, were diagnostic of a severe spinal muscular atrophy, complicated by involvement of brainstem nuclei and sensory nerves. Contrary to accepted criteria, weakness of extraocular muscles and facial weakness do not exclude the diagnosis of SMA.