Clinical Description
Werner syndrome is characterized by the premature appearance of features associated with normal aging and cancer predisposition. Individuals with Werner syndrome develop normally until the end of the first decade. The first symptom, often recognized retrospectively, is the lack of a growth spurt during the early teen years.
Symptoms typically start in the 20s. Initial findings include loss and graying of hair, hoarseness, and scleroderma-like skin changes, followed by bilateral ocular cataracts, type 2 diabetes mellitus, hypogonadism, skin ulcers, and osteoporosis in the 30s. Median age of diagnosis ranges from late 30s to 40s [Oshima et al 2017, Takemoto et al 2013].
Cataracts. Median age of onset of cataracts is approximately 31 years [Oshima et al 2017]. Bilateral cataracts are universal, and progress rapidly in individuals with Werner syndrome. Complications from surgical treatment are common and include (among others) wound dehiscence, peripheral anterior synechiae, epiretinal membrane formation, and cystoid macular edema [Lyons et al 2019]. Specific intraoperative and postoperative techniques (phacoemulsification, small incision size, use of viscoelastic to protect corneal endothelium, use of a weak topical steroid to avoid suppression of fibroblast proliferation) have been reviewed [Lyons et al 2019] in order to optimize outcome.
Facial features. A characteristic facial appearance, termed "bird-like" because of the pinched appearance at the bridge of the nose, evolves during the third or fourth decade.
Cardiovascular. Affected individuals exhibit several forms of arteriosclerosis; the most serious form, coronary artery atherosclerosis, may lead to myocardial infarction, which, together with cancer, is the most common cause of death. The mean age of death in individuals with Werner syndrome is 54 years [Oshima et al 2017]. Similarly, the median life span of Japanese individuals with Werner syndrome is 53 years [Goto et al 2013].
Malignancy. The spectrum of cancers in individuals with Werner syndrome is unusual in that it includes a large number of sarcomas and very rare cancer types in typical locations [Lauper et al 2013]. The most common cancers in Japanese individuals (for whom the most data exist) are soft-tissue sarcomas, osteosarcomas, melanomas, and thyroid carcinomas. Acral lentiginous melanomas (most often observed on the feet and nasal mucosa) are particularly prevalent compared to levels observed in the general population [Lauper et al 2013]. Common types of carcinomas have also been observed.
Osteoporosis. The osteoporosis of individuals with Werner syndrome is unusual in that it preferentially affects the long bones [Mori et al 2021]. In contrast, osteoporosis during normative aging preferentially involves the vertebral bodies, particularly in women. Characteristic osteolytic lesions of the distal phalanges of the fingers are observed on radiograph.
Skin. Deep, chronic ulcers around the ankles (Achilles tendon, medial malleolus, lateral malleolus) are highly characteristic [Kubota et al 2021].
Neurologic. Controversy exists concerning the degree to which the brain is involved. While individuals with Werner syndrome may have cerebrovascular disease resulting in stroke, they do not appear to be unusually susceptible to Alzheimer disease. Cognitive changes are not typically observed. Diffuse changes observed on brain MRI in some individuals warrant further investigation in research studies [De Stefano et al 2003].
Fertility. Fertility appears to decline soon after sexual maturity. This decline in fertility is associated with testicular atrophy and probable accelerated rate of loss of primordial follicles in the ovaries, although data are sparse. Early menopause is common in women, as are multiple miscarriages, but successful pregnancies have also been reported. Men have fathered children, usually at younger ages than in the general population.
Genotype-Phenotype Correlations
The chronologic order of the onset of signs and symptoms is similar in all individuals with Werner syndrome regardless of the specific WRN pathogenic variants.
The specific cell type in which cancer develops may depend on the type of WRN pathogenic variant present. In individuals of Japanese descent, papillary thyroid carcinoma has been associated with an N-terminal variant, whereas follicular thyroid carcinoma is more frequently observed with a C-terminal variant [Ishikawa et al 1999]. This finding clearly contradicts the original assumption that all identified WRN pathogenic variants result in truncation of the nuclear localization signal of WRN protein and thereby act as null variants.
The p.Arg834Cys allele is common in Latino populations, and results in reduced helicase and exonuclease activity in vitro, but multiple Mexican individuals homozygous for the allele have been reported to have no clinical features of Werner syndrome [Kamath-Loeb et al 2017].
Prevalence
The prevalence of Werner syndrome varies with the level of consanguinity in populations.
Apparent WRN founder variants contribute to higher prevalence in some populations. In the Japanese, the frequency ranges from about 1:20,000 to 1:40,000, based on the frequencies of detectable heterozygous pathogenic variants [Yokote et al 2017]. This is most likely the result of a founder variant in the Japanese population. Similarly, in the Sardinian population, the frequency is estimated at 1:50,000 [Yokote et al 2017].
Based on the population allele frequency of the most common pathogenic variant, c.1105C>T, which accounts for approximately 20% of pathogenic alleles, the prevalence of Werner syndrome is estimated at 1:380,000-1:1,000,000.