Schwannosis in Three Foals and a Calf.
Authors: Miranda Ileana C, Taylor Kyle R, Castleman William, de Lahunta Alexander, Summers Brian A, Miller Andrew D
Journal: Veterinary pathology
Summary
Schwannosis—the aberrant proliferation of Schwann cells within the spinal cord parenchyma—has been documented extensively in human neurofibromatosis type-2 but was previously unrecognised as a spontaneous condition in livestock until this pathological investigation of three foals and one calf presenting with progressive neurological signs from birth between 5 and 11 weeks of age. Bilateral plaques of proliferative spindle cells were identified throughout multiple spinal cord levels in all cases, predominantly in white matter adjacent to dorsal and ventral nerve roots, with immunohistochemical markers (myelin protein zero and periaxin) confirming these cells originated from the peripheral nervous system rather than arising within the CNS itself. In two affected animals, disorganised neural tissue (glioneuronal hamartomas) created sufficient mass effect to cause syringohydromyelia, explaining the severity of clinical signs. The congenital presentation and cellular characteristics suggest this represents a developmental misdirection of Schwann cell migration during embryogenesis rather than acquired disease, raising important questions about whether schwannosis may be more prevalent in neonatal foals and calves than currently recognised. Clinicians should consider this diagnosis in young ruminants and equines presenting with progressive spinal cord dysfunction from birth, as early identification through advanced imaging and subsequent pathological confirmation could refine our understanding of congenital neurological conditions and potentially inform breeding decisions in affected families.
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Practical Takeaways
- •Schwannosis is a previously unrecognized congenital maldevelopment in domestic animals presenting as progressive neurological dysfunction in early life; clinicians should be aware of this diagnosis in neonates with unexplained spinal cord signs
- •This condition appears to result from spontaneous invasion of peripheral nervous system-derived Schwann cells into the central nervous system during development, suggesting abnormal embryologic development rather than an acquired disease
- •Progressive neurological signs in foals and calves with spinal cord involvement warrant histopathological and immunohistochemical examination to identify this rare but distinct pathological entity
Key Findings
- •Schwannosis (ectopic Schwann cell proliferation in CNS) was identified in 4 neonatal ruminants (3 foals, 1 calf) aged 5–11 weeks with progressive neurological signs from birth
- •Bilateral plaques of Schwann cells predominantly affected white matter adjacent to dorsal and ventral nerve roots with variable extension into gray matter at multiple spinal cord levels
- •Immunohistochemistry confirmed PNS myelin formation within the spinal cord using markers myelin protein zero and periaxin
- •Glioneuronal hamartomas were present in all cases; 2 animals developed syringohydromyelia secondary to mass effect