Lisa L. Wang

Clinical manifestations in a cohort of 41 Rothmund-Thomson syndrome patients

Rothmund-Thomson syndrome (RTS) is a rare autosomal recessive genodermatosis characterized by a poikilodermatous rash starting in infancy, small stature, skeletal abnormalities, juvenile cataracts, and predisposition to specific cancers. We have identified a contemporary cohort of 41 patients to better define the clinical profile, diagnostic criteria, and management of patients with RTS. Patients with the diagnosis of RTS were ascertained by referrals from dermatology, ophthalmology, genetics, and oncology or from direct contact with the patients family. Medical information was obtained from interviews with physicians, patients, and their parents and a review of medical records. The age range at ascertainment was 9 months to 42 years (28 males and 13 females; M:F, 2:1). All subjects displayed a characteristic rash. Thirteen subjects had osteosarcoma (OS) (32%), eight had radial defects (20%), seven had gastrointestinal findings (17%), two had cataracts (6%), and one had skin cancer (2%). Twenty-two of 28 patients without OS were less than 15 years old and thus remain at significant risk for this tumor. This case-series study reveals a clinical profile of RTS that includes a higher prevalence of OS and fewer cataracts, compared with historical reports. These differences may reflect either allelic or genetic heterogeneity. This study documents the frequency of clinical anomalies in a contemporary cohort of RTS patients and revises guidelines for diagnosis and management of RTS.

The mutation spectrum in RECQL4 diseases.

Mutations in the RECQL4 gene can lead to three clinical phenotypes with overlapping features. All these syndromes, Rothmund–Thomson (RTS), RAPADILINO and Baller–Gerold (BGS), are characterized by growth retardation and radial defects, but RAPADILINO syndrome lacks the main dermal manifestation, poikiloderma that is a hallmark feature in both RTS and BGS. It has been previously shown that RTS patients with RECQL4 mutations are at increased risk of osteosarcoma, but the precise incidence of cancer in RAPADILINO and BGS has not been determined. Here, we report that RAPADILINO patients identified as carriers of the c.1390+2delT mutation (p.Ala420_Ala463del) are at increased risk to develop lymphoma or osteosarcoma (6 out of 15 patients). We also summarize all the published RECQL4 mutations and their associated cancer cases and provide an update of 14 novel RECQL4 mutations with accompanying clinical data.

Intron-Size Constraint as a Mutational Mechanism in Rothmund-Thomson Syndrome

Rothmund-Thomson syndrome (RTS) is an autosomal recessive disorder caused by deleterious mutations in the RECQL4 gene on chromosome 8. The RECQL4 gene structure is unusual because it contains many small introns <100 bp. We describe a proband with RTS who has a novel 11-bp intronic deletion, and we show that this mutation results in a 66-bp intron too small for proper splicing. Constraint on intron size may represent a general mutational mechanism, since human-genome analysis reveals that approximately 15% of genes have introns <100 bp and are therefore susceptible to size constraint. Thus, monitoring of intron size may allow detection of mutations missed by exon-by-exon approaches.

Sensitivity of RECQL4-deficient fibroblasts from Rothmund-Thomson syndrome patients to genotoxic agents

RECQ helicase protein-like 4 (RECQL4) is a member of the human RECQ family of DNA helicases. Two-thirds of patients with Rothmund–Thomson syndrome (RTS) carry biallelic inactivating mutations in the RECQL4 gene. RTS is an autosomal recessive disorder characterized by poikiloderma, sparse hair, small stature, skeletal abnormalities, cataracts, and an increased risk of cancer. Mutations in two other RECQ helicases, BLM and WRN, are responsible for the cancer predisposition conditions Bloom and Werner syndromes, respectively. Previous studies have shown that BLM and WRN-deficient cells demonstrate increased sensitivity to hydroxyurea (HU), camptothecin (CPT), and 4-nitroquinoline 1-oxide (4NQO). Little is known about the sensitivity of RECQL4-deficient cells to these and other genotoxic agents. The purpose of this study was to determine if RTS cells display any distinct cellular phenotypes in response to DNA damaging agents or replication blocks that could provide insight into the molecular function of the RECQL4 protein. Our results show that primary fibroblasts from RTS patients carrying two deleterious RECQL4 mutations, compared to wild type (WT) fibroblasts, have increased sensitivity to HU, CPT, and doxorubicin (DOX), modest sensitivity to other DNA damaging agents including ultraviolet (UV) irradiation, ionizing radiation (IR), and cisplatin (CDDP), and relative resistance to 4NQO. The RECQ family of DNA helicases has been implicated in the regulation of DNA replication, recombination, and repair. Because HU, CPT, and DOX exert their effects primarily during S phase, these results support a greater role for the RECQL4 protein in DNA replication as opposed to repair of exogenous damage.

Clinicopathologic Features of Osteosarcoma in Patients With Rothmund-Thomson Syndrome

PURPOSE Patients with Rothmund-Thomson syndrome (RTS) and RECQL4 gene mutations have an increased risk of developing osteosarcoma (OS). Because RTS is considered a genomic instability syndrome, patients may experience increased toxicity with chemotherapy. The purpose of this study was to summarize the clinical features and response to therapy of OS in patients with RTS. The results of this analysis will help to define treatment guidelines for this complex and rare condition. PATIENTS AND METHODS An international cohort of patients with RTS and OS was enrolled in an institutional review board-approved study at Baylor College of Medicine (Houston, TX). Medical records were reviewed, and the following information was extracted: clinical features, treatment, pathologic findings, and clinical outcome. RESULTS The median age at diagnosis of OS for the 12 patients was 10 years. The most common primary tumor sites were the long bones (femur, tibia); the most frequent histologic subtype was conventional OS. Histologic response to chemotherapy and outcome were similar to other published large series of sporadic OS. Eight patients are alive and disease free; four died as a result of cancer. Five patients required chemotherapy dose modifications, most commonly due to mucositis from doxorubicin. CONCLUSION Our results indicate that patients with RTS and OS are younger, but that their clinical behavior is similar to patients with sporadic OS. Our report suggests that these patients should initially be treated with conventional doses of chemotherapy as prescribed by current protocols; however, cautious and careful clinical observation is warranted to monitor for enhanced doxorubicin sensitivity in patients with RTS.

Radiographic Abnormalities in Rothmund-Thomson Syndrome and Genotype–Phenotype Correlation with RECQL4 Mutation Status

OBJECTIVE The purpose of this study was to summarize the radiographic skeletal findings in patients with Rothmund-Thomson syndrome (RTS) and to determine whether there is an association between the presence of skeletal abnormalities and the mutational status of the RECQL4 gene. SUBJECTS AND METHODS Twenty-eight subjects with RTS underwent skeletal surveys and RECQL4 DNA mutation testing. Radiographs were reviewed by two radiologists. RECQL4 mutation testing by DNA sequencing of the gene was performed by a diagnostic laboratory. Genotype-phenotype analysis by Fishers exact test was performed to investigate whether there was a correlation between mutation status and skeletal abnormalities. RESULTS Twenty-one (75%) of the subjects had at least one significant skeletal abnormality, the more common being abnormal metaphyseal trabeculation, brachymesophalangy, thumb aplasia or hypoplasia, osteopenia, dislocation of the radial head, radial aplasia or hypoplasia, and patellar ossification defects. Three subjects had a history of destructive bone lesion (osteosarcoma). Genotype-phenotype analysis showed a significant correlation between RECQL4 mutational status and the presence of skeletal abnormalities (p < 0.0001). CONCLUSION Skeletal abnormalities are frequent in persons with RTS. Many of these abnormalities are not clinically apparent but are detectable on radiographs. The presence of skeletal abnormalities correlates with RECQL4 mutation status, which has been found to correlate with risk of osteosarcoma. Skeletal surveys aid in both diagnosis and management of RTS.

Identification of a novel C16orf57 mutation in Athabaskan patients with Poikiloderma with Neutropenia

Poikiloderma with Neutropenia (PN), Clericuzio‐Type (OMIM #604173) is characterized by poikiloderma, chronic neutropenia, recurrent sinopulmonary infections, bronchiectasis, and nail dystrophy. First described by Clericuzio in 1991 in 14 patients of Navajo descent, it has since also been described in non‐Navajo patients. C16orf57 has recently been identified as a causative gene in PN. The purpose of our study was to describe a spectrum of C16orf57 mutations in a cohort of PN patients including five patients of Athabaskan (Navajo and Apache) ancestry. Eleven patients from eight kindreds were enrolled in an IRB‐approved study at Baylor College of Medicine. Five patients were of Athabaskan ancestry. PCR amplification and sequencing of the entire coding region of the C16orf57 gene was performed on genomic DNA. We identified biallelic C16orf57 mutations in all 11 PN patients in our cohort. The seven new deleterious mutations consisted of deletion (2), nonsense (3), and splice site (2) mutations. The patients of Athabaskan ancestry all had a common deletion mutation (c.496delA) which was not found in the six non‐Athabaskan patients. Mutations in the C16orf57 gene have been identified thus far in all patients studied with a clinical diagnosis of PN. We have identified seven new mutations in C16orf57 in PN patients. One of these is present in all patients of Athabaskan descent, suggesting that c.496delA represents the PN‐causative mutation in this subpopulation.

Absence of RECQL4 mutations in poikiloderma with neutropenia in Navajo and non-Navajo patients

Poikiloderma with neutropenia (PN), previously referred to as Navajo poikiloderma (MIM #604173) is a rare, autosomal recessive disorder first described by Clericuzio et al. [1991] in the Navajo American Indian population [Erickson, 1999]. It is characterized by a distinctive poikilodermatous rash, noncyclical neutropenia, small stature, pachyonychia, and pulmonary disease (reactive airway disease and recurrent pulmonary infections). Themolecular defect in this disorder has not been identified. PN shares some overlapping clinical features with Rothmund-Thomson syndrome (RTS, MIM #268400), another autosomal recessive disorder characterized by poikiloderma, small stature, and nail abnormalities. In addition, RTS patients have skeletal manifestations, sparse hair, cataracts, and predisposition to malignancy, specifically osteosarcoma [Wang et al., 2001], not reported in PN. Both disorders are defined by poikilodermatous skin changes, but the pattern of the rash differs. InRTS, the rash typically starts in infancyon the cheeks as macular erythema (acute phase) and then spreads to involve the extremities, rarely affecting the trunk and abdomen. The rash of PN tends to start more peripherally as papular eczematous erythema which then spreads centrally to involve the trunk and face. The skin changes of both disorders ultimately evolve into a more chronic phase of poikiloderma. Whereas neutropenia is classically associated with PN but not RTS, an increasing number of cases of hematologic abnormalities are being reported in RTS, including isolated neutropenia [Welch et al., 1984], myelodysplastic syndrome [Rizzari et al., 1996], leukemia [Porter et al., 1999], and aplastic anemia [Knoell et al., 1999]. Mutations in the RECQL4 gene at 8q24.3 encoding a DNA helicase have been detected in approximately two-thirds of RTS patients [Kitao et al., 1999; Lindor et al., 2000; Wang et al., 2002]. To examinewhether PN could be due to homozygosity for a particular allele at the RTS locus, we performed sequence analysis of the RECQL4 gene in three kindredswith the PNphenotype. One kindred included two affectedNavajo siblings; the secondkindredhada single affected child of Turkish and British descent; and the third kindred consisted of affected fraternal twins of Scottish descent. All subjects or their parents provided informed consent to participate in a research protocol approved by the Institutional Review Board for Human Subjects Research of Baylor College of Medicine, Houston, TX. The two Navajo subjects were sisters (ages 15 and 13 years at time of ascertainment) who had the classic rash of PN and neutropenia. Other findings included frequent infections in the first year of life, such as recurrent pneumonia with associated wheezing and recurrent otitismedia. Theyhadmarked thickening and excessive curving of the fingernails and toenails. The Turkish/British subject was a 2-year-old female who carried an initial diagnosis of probable RTS. However her clinical findings were more consistent with PN. Her rash started at age 3 months on her lower extremities, then spread to involve upper extremities, and eventually more centrally to involve her trunk and face. It began as a mottled pink/red rash with an eczematous component and over time became more hyperpigmented and poikilodermatous. She had pachyonychia, especially of the toenails. She was found at age 20 months to have severe neutropenia (ANC 0.3 10/ul) that persisted and was noncyclical. Bone marrow examination was normal. Her growth (25th centile for weight and height) and development have been without delay. Chromosome analysis was normal (46, XX). The third kindred consisted of 2-year-old male (sibling A) and female (sibling B) fraternal twins from Scotland who were born at 36 weeks gestation to nonconsanguineous parents. At the age of 2 months they developed an eczematous rash initially on the arms and legs and subsequently on the face. Gradually the eczema cleared and was replaced by poikiloderma (Fig. 1A and B). They also exhibited nail dystrophy starting at 3 weeks of age with subungual hyperkeratosis (Fig. 2). The nails were markedly thickened and difficult to cut. Both children had recurrent respiratory Grant sponsor: National Institutes of Health; Grant numbers: HD24064, K12 HD41648-01, K08 HD42136-01.

Recommendations for Childhood Cancer Screening and Surveillance in DNA Repair Disorders

DNA repair syndromes are heterogeneous disorders caused by pathogenic variants in genes encoding proteins key in DNA replication and/or the cellular response to DNA damage. The majority of these syndromes are inherited in an autosomal-recessive manner, but autosomal-dominant and X-linked recessive disorders also exist. The clinical features of patients with DNA repair syndromes are highly varied and dependent on the underlying genetic cause. Notably, all patients have elevated risks of syndrome-associated cancers, and many of these cancers present in childhood. Although it is clear that the risk of cancer is increased, there are limited data defining the true incidence of cancer and almost no evidence-based approaches to cancer surveillance in patients with DNA repair disorders. This article is the product of the October 2016 AACR Childhood Cancer Predisposition Workshop, which brought together experts from around the world to discuss and develop cancer surveillance guidelines for children with cancer-prone disorders. Herein, we focus on the more common of the rare DNA repair disorders: ataxia telangiectasia, Bloom syndrome, Fanconi anemia, dyskeratosis congenita, Nijmegen breakage syndrome, Rothmund–Thomson syndrome, and Xeroderma pigmentosum. Dedicated syndrome registries and a combination of basic science and clinical research have led to important insights into the underlying biology of these disorders. Given the rarity of these disorders, it is recommended that centralized centers of excellence be involved directly or through consultation in caring for patients with heritable DNA repair syndromes. Clin Cancer Res; 23(11); e23–e31. ©2017 AACR. See all articles in the online-only CCR Pediatric Oncology Series.

Aging in Rothmund-Thomson syndrome and related RECQL4 genetic disorders

Rothmund-Thomson Syndrome (RTS) is a rare autosomal recessive disease which manifests several clinical features of accelerated aging. These findings include atrophic skin and pigment changes, alopecia, osteopenia, cataracts, and an increased incidence of cancer for patients carrying RECQL4 germline mutations. Mutations in RECQL4 are responsible for the majority of cases of RTS. RECQL4 belongs to RECQ DNA helicase family which has been shown to participate in many aspects of DNA metabolism. In the past several years, accumulated evidence indicates that RECQL4 is important not only in cancer development but also in the aging process. In this review, based on recent research data, we summarize the common aging findings in RTS patients and propose possible mechanisms to explain the aging features in these patients.