Trisomy 18 with widespread calcinosis cutis

Trisomy 18 is the second most common autosomal trisomy, associated with high mortality, with only 5-10% of affected individuals surviving beyond the first year of life. Consequently, comorbidities in long-term survivors are rarely reported. We describe the case of a 6-year-old East Asian girl with trisomy 18 who presented with calcinosis cutis. The patient initially developed a firm, non-tender subcutaneous nodule on the left wrist, which later spread to the forearm and upper arm. Physical examination and imaging revealed extensive subcutaneous nodules in other extremities. High-frequency ultrasonography showed hypoechogenic masses with posterior acoustic shadows, while skin biopsy revealed fat necrosis and calcium deposition. No significant abnormalities were detected in the levels of calcium, phosphorus, parathyroid hormone or vitamin D. Based on laboratory findings and the patient's medical history, metabolic, nutritional, inflammatory and iatrogenic causes of calcinosis cutis were unlikely. Consequently, the condition was classified as either dystrophic or idiopathic calcinosis cutis. The patient was managed as an outpatient without specific treatment. This report discusses the mechanisms of calcinosis cutis and the reasons for the limited research on its association with trisomy 18. To our knowledge, this is the first report describing calcinosis cutis as a concomitant condition in a paediatric patient with trisomy 18, and it is anticipated that increased awareness of this disease may lead to a rise in reported cases in the future.