CIDP: Childhood onset, Chronic

• Met strict criteria for CIDP
• Had weakness for more than 2 years
• Improved prominently in strength & ADL after corticosteroid treatment

Nerve: Moderate severity

Toluidine blue stain Numerous thinly myelinated large axons Small onion bulbs

Toluidine blue stain Large axons surrounded by small onion bulbs

Toluidine blue stain

Toluidine blue stain Patchy involvement within one fascicle
Toluidine blue stain Region of fascicle with relatively abundant large axons	Toluidine blue stain Region of fascicle with few large axons Smaller myelinated and unmyelinated axons predominate

Nerve: Onion bulbs prominent

Toluidine blue stain Large onion bulbs

Toluidine blue stain

Toluidine blue stain Onion bulbs: Patchy distribution

Toluidine blue stain Onion bulbs: Around axons with thicker myelin sheath

Nerve: Infantile onset neuropathy

Toluidine blue stain Small axons: Very thin myelin sheath

Toluidine blue stain

Muscle: Type 1 predominance is common

ATPase, pH 9.4 stain Type 1 muscle fiber predominance