Clinical Description
Rothmund-Thomson syndrome (RTS) is a genetic disorder associated with a characteristic skin rash in combination with certain other findings detailed in this section. One subset of affected individuals defined by the lack of RECQL4 pathogenic variants (historically referred to as type 1 RTS) is predisposed to developing juvenile cataracts but not osteosarcoma when followed over time. The other, larger subset of individuals with RTS and RECQL4 pathogenic variants (historically referred to as type 2 RTS) is at increased risk of developing osteosarcoma and other cancers, and these individuals are also more likely to have skeletal abnormalities [Wang et al 2003]. It is important to keep in mind that there are phenotypic overlaps between types 1 and 2, and some individuals have not had any abnormality found on molecular genetic testing thus far.
Variability. Individuals with RTS can exhibit few or many of the associated clinical features. The severity of the features (e.g., rash) also varies.
Skin. Children with RTS typically develop a rash between ages three and six months but occasionally as late as age two years. The skin changes begin as erythema, swelling, and occasionally blistering on the face, then spread to the buttocks and extremities. Gradually over a period of months to years the skin changes become chronic, with reticulated hypo- and hyperpigmentation, telangiectasias, and punctate atrophy (collectively referred to as poikiloderma) that persist throughout life.
Hyperkeratotic lesions occur in approximately one third of individuals.
Uncommon but reported findings [Mak et al 2006] include the following:
Calcinosis, the formation of calcium deposits in the skin, usually at the site of an injury
Note: Calcinosis cutis differs from osteoma cutis, which is true bone formation.
Porokeratosis, a sign of disordered keratinization. This has been reported in one person with RTS, and thus may or may not be a related finding.
Teeth. Many individuals with RTS also have dental abnormalities including rudimentary or hypoplastic teeth, microdontia, delayed eruption, supernumerary and congenitally missing teeth, ectopic eruption, and increased incidence of caries [Haytaç et al 2002].
Hair. Children with RTS may have sparse scalp hair or even total alopecia. Eyelashes and/or eyebrows may also be sparse or absent.
Growth. Most individuals with RTS are the result of a full-term pregnancy but tend to have low birth weight and length for gestational age. They remain small throughout their lives, usually below the fifth percentile for both weight and height. Growth hormone levels are usually normal.
Skeleton. A study of 28 individuals with RTS examined by skeletal survey found that 75% had at least one major skeletal abnormality [Mehollin-Ray et al 2008]. Findings included abnormal trabeculation with longitudinal and transverse metaphyseal striations, dysplastic changes in the phalanges, absent or malformed bones (e.g., aplastic radii, malformed ulnae, hypoplastic thumbs), fused bones, osteopenia, and hypoplastic or absent patella. These skeletal findings are more often seen in individuals with type 2 RTS, caused by pathogenic variants in RECQL4.
In a study of metabolic bone disease in 29 individuals with a clinical diagnosis of RTS, a significant proportion were found to have decreased bone mineral density as well as history of fractures [Cao et al 2017]. Additionally, the presence of pathogenic variants in RECQL4 and low bone mineral density correlated with the history of increased risk of fractures [Cao et al 2017].
Gastrointestinal. Some infants or young children with RTS have feeding difficulties or other gastrointestinal problems including chronic emesis or diarrhea. Although feeding tubes are occasionally required, most of these problems resolve spontaneously during childhood [Wang et al 2001].
Hematologic. Benign and malignant hematologic abnormalities including isolated anemia and neutropenia, myelodysplasia, aplastic anemia, and leukemia have been reported in individuals with RTS [Knoell et al 1999, Porter et al 1999, Narayan et al 2001, Pianigiani et al 2001].
Cataract. The prevalence of juvenile cataracts has been reported in some series to be as high as 50%, with onset usually between ages three and seven years. In an international cohort of 41 individuals with RTS (age range 9 months to 42 years), the prevalence of cataracts was found to be much lower (<10%) [Wang et al 2001]. Earlier onset (as early as the first few months of life) and later onset (teens or adulthood) have also been reported. Most of the reports of early-onset, bilateral juvenile cataracts come from descriptions from Europe; these individuals are more likely to represent type 1 RTS, caused by pathogenic variants in ANAPC1 [Ajeawung et al 2019]
Cancer. The overall prevalence of cancers in adults with RTS is unknown.
Osteosarcoma is the most commonly reported malignancy [
Wang et al 2003]. In a cohort of those with RTS, the prevalence of osteosarcoma was 30% [
Wang et al 2001]. The median age at diagnosis, 11 years, was slightly younger than that seen in the general population. Families in which more than one sib had RTS and osteosarcoma have been identified [
Lindor et al 2000,
Wang et al 2001]. Osteosarcoma is associated with type 2 RTS.
Skin cancer. Individuals with RTS are also at increased risk of developing skin cancer, including basal cell carcinoma and squamous cell carcinoma [
Borg et al 1998] and melanoma [
Howell & Bray 2008]. The prevalence of skin cancers in individuals with RTS is estimated from the literature to be 5%. Skin cancer can occur at any age, although it often occurs earlier than in the general population. The mean age for epithelial tumors has been estimated at 34.4 years [
Stinco et al 2008].
Piquero-Casals et al [2002] report on a consanguineous Brazilian family with classic features of RTS including poikiloderma and bilateral cataracts. All three affected sibs developed cutaneous squamous cell carcinoma in adulthood (age 35-48 years). The cancers occurred on non-sun-exposed surfaces. Skin cancer occurs in individuals with both type 1 and type 2 RTS.
Second malignancy. A few individuals with RTS have been reported to have a second malignancy. One developed non-Hodgkin lymphoma nine years after chemotherapy for osteosarcoma [
Spurney et al 1998], and another developed Hodgkin lymphoma eight years after therapy for osteosarcoma [
Wang et al 2001]. In general, follow-up time for individuals with RTS and osteosarcoma has been too short to draw conclusions about the risk of secondary malignancy.
Multiple primary cancers have also been reported in individuals with RTS. For example, one affected individual developed anaplastic large-cell lymphoma at age nine years, diffuse large-cell B lymphoma and osteosarcoma at age 14 years, and acute lymphoblastic leukemia at age 21 years. Whether the latter cancers represent secondary malignancies is not known [
Simon et al 2010].
Chemotherapy effects. Because RTS is felt to be a chromosome instability syndrome, those treated for malignancy may in theory be more sensitive to the effects of chemotherapy and at a higher risk for second malignancy. However, from the limited number of individuals reported, it appears that most individuals with RTS and cancer treated with chemotherapy have not had significantly increased toxicities, although some individuals may experience increased mucositis with doxorubicin treatment [
Hicks et al 2007,
Simon et al 2010]. Other individuals have reported increased toxicities after treatment with high-dose methotrexate, but side effect profiles vary significantly among individuals and appear to be specific to the individual.
Other. Infertility has been described in affected males and females; however, a few affected females have had normal pregnancies, and a few males have produced offspring.
Immunologic function appears to be intact. However, there are several isolated reports of individuals with RTS who have concomitant immune dysfunction. These include an individual who had humoral immune deficiency associated with granulomatous skin lesions [De Somer et al 2010], an affected individual with IgG4 deficiency and recurrent sinopulmonary infections [Kubota et al 1993], and another affected individual with low serum immunoglobulin (IgG and IgA) levels who presented with herpes encephalitis [Ito et al 1999]. One individual with RTS and severe combined immunodeficiency (T-B+NK- phenotype with agammaglobulinemia) underwent successful hematopoietic stem cell transplantation [Broom et al 2006].
Most individuals with RTS appear to have normal intelligence.
Life span. In the absence of malignancy, life span is probably normal, although follow-up data in the published literature are limited. Death from metastatic osteosarcoma and other cancers has been reported in a number of children and adults with RTS.