Endocrine Abstracts

A 35-year-old gentleman was referred to our Endocrinology department by Moorfields Eye hospital. He reported a one-year history of visual decline in his right eye, which led to prescription glasses, and incidental finding of bilateral conjunctival nodules. He had reduced visual acuity (pinhole right eye: 6/24 and left eye 6/6) and prominent corneal nerves on slit-lamp examination. He underwent an excisional biopsy of the conjunctival nodules confirming bilateral conjunctival neuromas; prompting an urgent Endocrinology referral due to the known association with MEN2B syndrome. He denied any symptoms related to phaeochromocytoma or medullary thyroid cancer. His past medical history included complex Crohn’s disease resistant to biological treatment and infective endocarditis of the pulmonary valve related to his Hickmann line which was inserted for nutritional optimisation. His other medical history included renal stones and recent cholecystectomy for a perforated gallbladder. There was no personal or family history of endocrinopathies. He recently had a 7-month-old son, conceived by IVF, due to oligozoospermia. On examination he was tall (height of 183.1 cm), with a marfanoid habitus. His BMI was 16 kg/m2. His BP was 114/70mmHg. He had a high arched palate, tongue, and conjunctival neuromas. He had evidence of previous abdominal surgeries. The rest of his systems examination was unremarkable including neck and visual fields. His serum adjusted calcium, phosphate, parathyroid hormone, thyroid function, calcitonin, carcino-embrional antigen, and plasma and urinary metanephrines were unremarkable. Genetic testing did not reveal a pathogenicity in the RET proto-oncogene associated with MEN2B. Exome sequencing revealed a heterozygous pathogenic SOS1 (son of sevenless-1) frameshift mutation, suggestive of pure mucosal neuroma syndrome (MNS). This is the second ever reported case in literature of a patient with pure MNS associated with ocular manifestations. Pure MNS is a recently described clinical entity distinct from MEN2B with typical physical features of MEN2B including marfanoid habitus and mucosal neuromas, but without the associated endocrinopathies (medullary thyroid carcinoma or pheochromocytoma) and RET mutation. Due to the rarity of MNS, the implications on long term screening, management and genetic counselling remain uncertain. As endocrinologists, it is important to be aware and distinguish between pure MNS from MEN2B to avoid unnecessary prophylactic treatments such as thyroidectomy, as the offspring is at 50% risk of inheriting this variant.