Classic Timothy Syndrome Associated With Bilateral Border Digit Syndactyly: A Case Series.

Purpose: Timothy syndrome (TS) is characterized by congenital long-QT arrhythmia and limb syndactyly. Patients who undergo syndactyly repair with undiagnosed TS may have their abnormal cardiac electrical activity unmasked during surgery. The purpose of this study was to detail the extremity phenotype seen in patients with TS, which may help hand surgeons in their preoperative assessment.

Methods: This was a retrospective review of all patients with TS seen at our institution from 1998 to 2022. Descriptive statistics regarding their demographics, medical and surgical histories, and syndactyly phenotypes were obtained.

Results: Seven patients (5 males and 2 females) with TS were seen at our institution for multidisciplinary evaluation (median age at presentation was 23 months). Six patients had finger syndactyly and 5 had toe syndactyly. One patient did not have any extremity syndactyly and was noted to have a specific TS mutation known to lack musculoskeletal abnormalities. All patients with finger syndactyly had border digit involvement, with 5 out of 6 patients displaying syndactyly of the middle-ring and ring-little finger web spaces. Toe syndactyly was more heterogeneous, with 1 patient lacking any lower extremity syndactyly and others having variable involvement of the second-third, third-fourth, and fourth-little toe web spaces. Complexity ranged from simple to complete. Four patients had intraoperative cardiac events leading to TS diagnoses after surgery.

Conclusions: Bilateral border digit hand syndactyly, with or without bilateral toe syndactyly, should raise concerns for TS and prompt further investigation into potential cardiac disease to avoid perioperative cardiac morbidity and mortality.

Type Of Study/level Of Evidence: Therapeutic V.