Chakrabarty, B. et al. "Dystrophinopathy Diagnosis Made Easy: Skin Biopsy, an Emerging Novel Tool" The Journal of Child Neurology 2014 29 (4) 469-474.
Submitted by Leigh Ramos-Platt, MD
Skin biopsy is a relatively simple procedure. Punch biopsies contain smooth muscle. Patients with Duchenne Muscular Dystrophy have absence of dystrophin in smooth muscle. In this study, 119 patients (111 boys and 8 girls) with suspected muscular dystrophy underwent both a skin biopsy (from the anterior thigh) and a gold standard confirmatory test. All patients had multiplex PCR testing to look for exon duplications and deletions. If this was negative, they underwent a muscle biopsy. Of the 100 patients that were confirmed to have a dytrophinopathy, 98 had positive findings (absence of dystrophin) in their skin punch biopsies. There were 2 false negatives. Of the 19 patients that were confirmed to be negative by either PCR or muscle biopsy, 18 had negative findings (presence of dystrophin) in their skin biopsy. There was one false positive. The authors concluded that skin punch biopsy is a relatively simple and non-invasive diagnostic tool to confirm the clinical suspicion of a dystrophinopathy.
While a sensitivity of 98% is encouraging while developing diagnostic tools, it is not certain that this will have a role in the practice of neuromuscular clinics. Most clinics proceed to dystrophin gene sequencing if there is clinical suspicion for a dystrophinopathy and the PCR or MLPA is negative for a duplication or deletion of an exon. With exon skipping and STOP codon read through trials available, just knowing that a patients has lack of dystrophin is not enough. Genetic confirmation is ideal. This technique may be more important as a measurement tool of how a particular therapy is working.