A Novel Homozygous WRN Mutation Identified in a Middle Aged Man With Diabetes Mellitus Complicated By Multiple Features of Accelerated Aging

Abstract

Background: Werner syndrome (WS; MIM# 277700) is a rare genetic disorder characterized by accelerated aging and predisposition to cancers. The causal gene, WRN, encodes a multifunctional nuclear protein that belongs to the RecQ family of DNA helicases. The earliest sign of WS is short stature due to the lack of pubertal growth spurt. In addition to the aged-appearance, WS patients typically develop functional declines of multiple organs including the endocrine system in their middle ages. Frequent Endocrine disorders include Type 2 Diabetes (T2D), dyslipidemia (DL), hypothyroidism, hypogonadism and osteoporosis. Most common causes of deaths are myocardial infarction and cancers in their 50s. Clinical Case: A 54-year old man was admitted for right wrist septic arthritis. His medical history was pertinent for premature cataract diagnosed in his 2nd decade. He had uncontrolled T2D (peak HbA1C level 10%) since the age of 32 years, treated with oral hypoglycemics including glimepiride, sitagliptin and metformin then shifted to insulin over the past 2 years. He also had DL since the age of 41 years, characterized by hypertriglyceridemia (766 mg/dL) with very low HDL (7 mg/dL). At age 50, he was diagnosed with hypothyroidism and negative anti-TPO antibodies. Moreover, he had refractory bilateral leg ulcers that manifested at the age of 35 years requiring multiple debridments, premature coronary artery disease at the age of 38 years and ischemic cardiomyopathy. On examination, his height was 154 cm and weight 42 kgs. He had prominent eyes, a pinched nose, grey and sparse scalp hair with absence of eyebrows and eyelashes. Hoarse voice was easily noticeable. He had very thin limbs, flat feet, central fat distribution and muscle wasting. Skin was shiny, tight, and atrophic with overlying hypermelanosis. Old bilateral hyperkeratotic deep feet ulcers were noticed with variable necrosis. Blood chemistry testing showed: HbA1C 8.2%, disturbed lipid profile, TG 341 mg/dL, HDL 17 mg/dL, LDL 155 mg/dL, and TSH 21 µU/mL (0.2 - 4.2 µU/mL). MRI of the foot revealed Achilles’ tendon calcification. His parents were 2nd degree cousins and had normal features. Three of his siblings had similar features and premature death. His diabetes was atypical due to his low BMI, high insulin requirements and the relatively early onset. WS was suspected based on the overall features of accelerated aging with characteristic deep leg ulcers and the family history. Genetic sequence analysis revealed a novel pathogenic homozygous nonsense variant mutation c.1111G>T, p.Glu371* of the WRN gene. Conclusion: Werner syndrome is a rare genetic disease, but it carries high morbidity and mortality burden, in addition to impaired quality of life. It should be highly suspected in patients with atypical T2D, DL, premature coronary disease, refractory leg ulcers with features of accelerated aging and short stature.