L1CAM and hereditary spastic paraplegia: However, it must be acknowledged that genes with truly tissue‐specific expression (e.g., brain‐ or muscle‐specific genes, e.g., DMD [Duchenne muscular dystrophy], NEB [nemaline myopathy], and L1CAM [hereditary spastic paraplegia]) will remain undetectable from any blood‐based RNA‐seq, suggesting that RNA‐seq from PHACs may be underpowered to detect relevant transcriptional aberrations in certain genes [8].