Macrophages: A minimally invasive tool for monitoring collagen VI myopathies.

Introduction: Collagen VI expression was tested in peripheral blood macrophages from patients with collagen VI–related myopathies and compared with muscle biopsy. Methods: RNA and protein studies were performed in blood macrophages from 5 patients previously diagnosed with either Ullrich congenital muscular dystrophy (UCMD) or Bethlem my- opathy (BM). The full spectrum of possible genotypes was con- sidered, including both dominant and recessive UCMD and BM cases. Results: In the dominant BM patient, no collagen VI alterations were detectable in macrophages or muscle biopsy. In the remaining patients, the protein defect caused by the selected mutations, as well as the transcriptional abnormalities, were readily detectable in macrophages, at levels comparable to those observed in muscle biopsy samples and cultured skin fibroblasts. Conclusions: Our data support the suitability of pe- ripheral blood macrophages as a reliable, minimally invasive tool for supplementing or replacing muscle/skin biopsies in the diagnosis and monitoring of collagen VI–related myopathies.