As with other rare diseases, one of the main challenges with Rothmund-Thomson syndrome is correlating the genotype to a phenotype. There are several clinically recognizable features associated with RTS, such as a skin rash, short stature and skeletal abnormalities.
The main clinical symptom is a skin rash, which usually develops between three and six months of age. The rash begins in the face and spreads to the extremities, but the trunk and abdomen are usually unaffected. The redness of the skin is due to increased blood flow in the capillaries, which can lead to the swelling and blistering of the area. The rash progresses over time and is described by the term poikiloderma, a skin condition characterized by increased and decreased pigmentation. This is why Rothmund-Thomson is also referred to as poikiloderma congenitale.
The second major clinical sign for RTS is a delay in linear growth. Despite having normal growth hormone levels, patients are usually born small for their gestational age and have short stature throughout life. Their growth deficiency is usually accompanied by skeletal anomalies. This may include a prominent forehead, loss of nose height due to bridge collapse and some abnormalities of the long bones. All patients with the RECQL4 mutation have skeletal abnormalities.
RTS patients usually have normal neurocognitive development, but there are some exceptions which is attributed to the accelerated loss of neurons in the brain (Gelaw et al., 2004). The most common ocular sign is the presence of bilateral cataracts which develop early in life and may escalate to complete blindness. There are some instances of gastrointestinal problems during infancy, but are usually resolved during childhood.
Molecular genetic testing, clinical testing and cytogenetic testing are available for RTS. To date, only the RECQL4 gene locus has been found to be associated with RTS. Under clinical testing, sequence analysis of all the coding regions and short introns have reported to detect mutations in approximately 66% of patients with RTS (Wang et al., 2003b). Deletion/duplication analysis can also be carried out using quantitative real-time PCR in order to detect small deletions in the RECQL4 gene. Besides these, regular cytogenetic testing of lymphocytes or skin fibroblasts may detect anomalies in the region of chromosome 8 responsible for RTS. The abnormalities in this locus may include trisomy 8, partial 8q duplication, tetrasomy 8q) (Miozza et al., 1998). However, it is noteworthy that patients exhibiting RTS may have normal cytogenetic studies.
After initial diagnosis of RTS, the following examinations are recommended in order to evaluate the magnitude of the disease:
- Testing for skeletal dysplasias by undergoing skeletal radiographs within the age of five
- Since cataracts are a high risk for patients with RTS, ophthalmologic examinations are recommended
- A complete blood count should be evaluated
Past years have shown that Pulsed dye laser has been able to treat the telangiectasis of RTS. Cataracts that are significantly concerning should undergo surgical removal. RTS patients who develop cancer are recommended to undergo standard chemotherapy as treatment. Bone marrow biopsy or complete cell count should be evaluated for patients with evidence of anemia or cytopenias.
For prevention, it is best to avoid exposure to sunlight as it may worsen the rash in some patients. To prevent skin cancer, sunscreens may be used. Other than skeletal radiographs and yearly eye examinations, close observation for unusual skin colour or texture and counseling for the risk of related medical complications are also recommended for affected individuals (Wang et al., 2009).
Lesions seen in RTS
The following show images of lesions seen in the different regions of the body in patients with RTS. Images of the face/cheek, hands and leg/thigh are shown respectively. (Picture source: http://dermatlas.med.jhmi.edu/derm/result.cfm?OMIM=268400)
The images shows affected body regions of a 9-year old girl who was diagnosed with RTS. During infancy, she suffered from intense rash in the sun-exposed areas of her body. Progressively she developed poikiloderma which extended in regions that were sun protected. She uses sunscreen and can play outdoors at school.
- Gene Review: Rothmund-Thomson Syndrome
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