Isolated premature menarche in two siblings with Neurofibromatosis type 1

Objectives Neurofibromatosis type 1 (NF1) is an autosomal dominant genetic disorder, caused by mutation in NF1. The condition is typified by the development of benign and malignant tumours in both the central nervous system and peripheral tissues. Isolated menarche is a sub-classification of incomplete isosexual precocious puberty typified by menarche in girls with no other features of pubertal development. The effects of NF1 on pubertal timing are poorly understood, we report two siblings with NF1 and apparent abnormal pubertal development. Case Presentation Two siblings were referred to the tertiary paediatric endocrinology clinic at 6 and 7 years of age with recurrent, cyclical vaginal bleeding. There was a strong family history of NF1, the mother of the siblings and two brothers were also diagnosed at a young age. On examination both patients were prepubertal at presentation. Both siblings underwent a gonadotrophin releasing hormone test, which revealed a follicle-stimulating hormone dominant (prepubertal) response. The features were suggestive of isolated premature menarche as no other cause was identified. The elder sibling established menarche and developed signs of consonant pubertal development at 12 years of age. The younger sibling remains under regular follow-up. Conclusions NF1 has previously been associated with alterations in pubertal timing. We report, for the first time, two siblings with NF1 who presented with isolated menarche.