NF1 and Osteopenia: In conclusion, by recruiting children with CPT and those with non-bone metabolic diseases, we found that the incidence of osteopenia in the CPT group was higher than that in the non-bone metabolic disease group, and SOS, STI, QUI and BMDe in the CPT group were lower than in the non-bone metabolic disease group, and this phenomenon is not related to NF1 but is related to CPT Crawford classification, suggesting that a higher CPT Crawford classification is associated with lower bone strength and higher risk of fracture.