Neurofibromatosis type 1: A comparison of the 1997 NIH and the 2021 revised diagnostic criteria in 75 children and adolescents.

Purpose: Examining a cohort of patients suspicious of neurofibromatosis type 1 (NF1) we compared the revised diagnostic criteria with the previous National Institutes of Health (NIH) diagnostic criteria. We asked whether the refinement improved distinguishing between NF1, Legius syndrome, and constitutional mismatch repair deficiency (CMMRD).

Methods: A database search in the hospital information system of the University Children's Hospital Augsburg between 2017 and 2020 ascertained patients with International Classification of Diseases-10 code Q85.0; their clinical phenotype was evaluated by retrospective chart review.

Results: A total of 75 patients were identified (median age 11.0 years [range 1.1-22.6 years]; 35 female). At first suspicion of NF1, 44 patients met the NIH criteria and 56 met the revised diagnostic criteria. In total, 12 patients were diagnosed with NF1 after performing molecular genetic testing. In 31 patients, only pigmentary findings were present, whereas nonpigmentary NF1 manifestations presented with time in 9 patients. In 1 patient a heterozygous variant of uncertain significance was identified in SPRED1. Requirements for CMMRD testing were fulfilled in another patient. A total of 3 patients presented with segmental clinical findings. Three additional patients did not meet the NIH criteria, 1 of them presented with 1 additional feature of CMMRD without fulfilling requirements for testing.

Conclusion: In our pediatric cohort, the revised diagnostic criteria discovered more patients with proven NF1 than the NIH criteria.