See:
Peach (Prunus persica) - Leaf Curl
Cause The fungus Taphrina bullata has been reported from Washington. Not a common issue in commercial production of pears likely due to pest control measures targeting other diseases and insects. Cultivars with symptoms during the spring of 2022 include Aniversarea, Bergamotte de Baillagrus, Comice, Doyenne d'Hiver, Dumn Adobe Pear, Early Harvest and Luscious. Symptoms were subtle on Bartlett.
Symptoms Large, light-green to yellow, irregular blisters form on the upper surface of leaves. A white fungal bloom develops on the concave underside. Blisters turn black in a few weeks looking more like a necrotic leaf spot that is difficult to identify from other potential problems.
The leaf blisters caused by eriophyid mites (pear rust mite, Epitrimerus pyri) are more common, smaller, can be reddish and are numerous on the leaf surface.
Reference Petrýdesová, J., Bacigálová, K. and Sulo, P. 2013. The reassignment of three 'lost' Taphrina species (Taphrina bullata, Taphrina insititiae and Taphrina rhizophora) supported by the divergence of nuclear and mitochondrial DNA. International journal of systematic and evolutionary microbiology, 63:3091-3098.