The aim in this study was to identify the incidence and de nova mutation rate of Neurofibramatosis type 1 (NF1) and describe the ocular and non-ocular findings in a population-based cohort of patients diagnosed over a 30-year period. The study included 50 people diagnosed with NF1 over a 30-year period yielding an annual incidence of 1.2/100,000 (0.8 to 1.5CI). Estimated prevalence rate was 0.10% over the 30 years. Mean age at diagnosis was 11.7 years with 72% diagnosed before the age of 18. Fifty-two were male and 44% had a positive family history of NF1 yielding de novo mutation rate of 56%. Characteristics included café-au-lait macules in 98%, freckling of axillary and inguinal regions in 74%, skeletal abnormalities in 30%, and neurofibromas in 46% (discrete cutaneous NF in 34% and plexiform NF in 16%). Ophthalmic findings included Lisch nodules in 52% (most bilateral), optic nerve glioma (2%) diagnosed at 26 years, strabismus in two patients, amblyopia in one patient, and congenital hypertrophy of the retinal pigment epithelium in one patient. Central nervous system (CNS) gliomas were found in 6%. Only one patient had a malignant nerve sheath tumour. One patient developed leukaemia and died at the age of three years. Limitations of this study were its retrospective design with incomplete data, some patients without diagnosis until at an older age, some may have been missed if cared for outside the catchment area and therefore the de novo mutation rate and incidence might be higher. The study may have underestimated the glioma rate. However, estimates of prevalence and mutation rates are similar to other published reports.
Neurofibromatosis type 1 features
Reviewed by Fiona Rowe
Neurofibromatosis type 1: a population-based study.
CONTRIBUTOR
Fiona Rowe (Prof)
Institute of Population Health, University of Liverpool, UK.
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