SAT613 A Novel NF1 Mutation As The Underlying Cause Of Dysmorphic Features And Acromegaly In An Atypical Case Of Neurofibromatosis Type 1

Disclosure: O. Alsagheir: None. L.A. Alobaid: None. M. Alswailem: None. H. Al-Hindi: None. A.S. Alzahrani: None. Introduction: Neurofibromatosis type 1 is an autosomal dominant disease with an estimated incidence of about 1:2000 cases. It is caused by genetic alterations in the gene NF1 encoding the tumor suppressor gene, neurofibromin. Patients with neurofibromatosis 1 are at an increased risk of a number of benign and malignant tumors including optic nerve gliomas, CNS tumors, malignant peripheral nerve sheath tumors, pheochromocytomas and many others. However, pituitary adenomas have been rarely described in neurofibromatosis type 1 and NF1 mutations have been found rarely in patients without manifestations of neurofibromatosis. In this report, we describe a patient with acromegaly who had some dysmorphic features but no clear skin or other manifestations of neurofibromatosis. He was found to have a deletion mutation in NF1 suggesting that his dysmorphic features and acromegaly are atypical manifestations of a previously undiagnosed neurofibromatosis type 1. Case Description: A 26-year-old-man presented at 18 years of age for evaluation of possible ventricular septal defect, which was ruled out by echocardiography, but he was found to have a subaortic membrane with moderate aortic regurgitation. He was also noticed to have coarse facial and body features which raised the possibility of acromegaly. He didn’t notice any facial changes, change in the size of hands and feet, headache or visual disturbances. In the family history, he reported that a number of his siblings are tall with large body habitus; none of them was evaluated or known to have medical illness. Physical examination: height 184 cm, weight 87 Kg, BMI 25, and BP 117/77 mmHg. He has frontal bossing, large supraorbital ridges, macrognathia, and hoarse deep voice but no skin tags, café au let spots, skin fibromas or freckling. Eye examination was unremarkable. Investigations: IGF-1 415 ng/ml (188-400), random GH 1.09 ng.ml (0.1-1.2). An oral glucose tolerance test showed baseline GH 0.99 increased to 8.05 ng/ml. An MRI of the pituitary gland showed a lobulated sellar and suprasellar heterogeneously enhancing pituitary adenoma. A Gallium 68 PET-CT scan showed an intense focus of uptake at the same location. Whole exome sequencing revealed a heterozygous NF1 mutation (NM_001128147.3: c.1782_*2del). This variant is likely pathogenic according to ACMG criteria. Conclusion: This case illustrates the value of whole exome sequencing for genetic testing in diagnosing atypical dysmorphia and other conditions when the diagnosis is not clear on clinical evaluation or conventional investigations. It also describes a rare association of acromegaly with neurofibromatosis. Presentation: Saturday, June 17, 2023