Digital necroses and vascular thrombosis in severe spinal muscular atrophy.
Infantile spinal muscular atrophy (SMA) caused by homozygous SMN1 gene deletions/mutations is characterized by neuronal loss and axonopathy of motor neurons. We report two unrelated patients with severe SMA type I who had only one SMN2 copy and developed ulcerations and necroses of the fingers and toes. Sural nerve biopsy was normal in patient 1, whose affected skin displayed necroses and thrombotic occlusions of small vessels. Corresponding to a mouse model and other patients with similar findings, we believe that severe survival motor neuron (SMN) deficiency may present as vasculopathy.