Two siblings with Cockayne syndrome are reported. In one case a sural nerve biopsy showed a demyelinating peripheral neuropathy with occasional inclusions in Schwann cells made up of electron dense finely granular material intermingled with vacuoles or lamellar structures. The significance, if any, of this accumulated material remains unclear. The presence, in addition, of small finely lamellar intra-axonal osmiophilic bodies suggests an associated axonal involvement.