We present a patient with poikiloderma, severe osteoporosis and a mild intellectual disability. At the age of 9 years, this patient was proposed to suffer from a novel disease entity designated as calcinosis cutis, osteoma cutis, poikiloderma and skeletal abnormalities (COPS) syndrome. At the age of 35, he was diagnosed with Hodgkin’s lymphoma. Recently, biallelic pathogenic variants in the RECQL4 gene were detected (c.1048_1049delAG and c.1391-1G>A), confirming a diagnosis of Rothmund-Thomson syndrome (RTS). In the brother of this patient, who had a milder phenotype, a similar diagnosis was made. ; Conclusion: We conclude that COPS syndrome never existed as a separate syndrome entity. Instead, osteoma cutis may be regarded as a novel feature of RTS, whereas mild intellectual disability and lymphoma may be underreported parts of the phenotype.What is new:• Osteoma cutis was not a known feature in Rothmund-Thomson patients.• Intellectual disability may be considered a rare feature in RTS; more study is needed.What is known:• RTS is a well-described syndrome caused by mutations in the RECQL4 gene.• Patients with RTS frequently show chromosomal abnormalities like, e.g. mosaic trisomy 8.