Trigger Digits in Mucopolysaccharidosis Type I: Clinical Characteristics, Surgical Outcomes, and Histopathological Findings

PURPOSE: Mucopolysaccharidosis type I (MPS-I), a genetic lysosomal storage disorder, often leads to musculoskeletal deformities such as trigger digits (TDs). Despite systemic therapies, connective tissues such as bone, muscle, and tendons remain difficult for the enzyme to reach, and TDs develop. We performed a retrospective study to assess the prevalence of TDs, evaluate surgical outcomes and recurrence, and explore accumulation of foam cell macrophages contributing to TD development in patients with MPS-I. METHODS: Data were obtained retrospectively from a cohort of 33 children born between 2001 and 2023. These patients were diagnosed with MPS-I and received yearly follow-up at our national reference center for MPS-I. Data on TD distribution, clinical symptoms, surgical outcomes, and histopathological slides were extracted from medical records. Survival curves and regression analyses were performed to evaluate cumulative risks and calculate hazard ratios. RESULTS: Thirteen patients (39%) with a median age at latest follow-up of 13.1 years (IQR, 8.8-17.9 years) were diagnosed with a total of 61 TDs at a median age of 5.3 years (IQR, 3.7-8.0 years). Most affected digits were the second, third, and fourth. Of 11 patients receiving a TD release, 2 patients had a recurrence. The overall cumulative risk of developing TDs was 57%. No significant association was observed for biochemical markers or age at transplantation. Despite successful hematopoietic stem cell transplantation, accumulation of degradation products was still observed in five of six patients, as evidenced by foam cell macrophages in histological sections of pulley tissue. These tissues were examined using routine staining and CD68 immunohistochemistry, as visualized using light microscopy. CONCLUSIONS: This study found that despite successful hematopoietic stem cell transplantation 39% of patients had developed TDs. A predominant distribution toward the second, third, and fourth digits was observed. Trigger digit release proved to be an effective treatment option in resolving symptoms of TDs, and recurrence of symptoms was seen in two patients. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic III.