The present disclosure provides methods for predicting a patient's response to biglycan therapy for diseases or conditions associated with an abnormal level or activity of biglycan; disorders associated with an unstable cytoplasmic membrane, for example, due to an unstable dystrophin associated protein complex (DAPC); disorders associated with abnormal synapses or neuromuscular junctions, including those resulting from an abnormal MuSK activation or acetylcholine receptor (AChR) aggregation. Examples of such diseases include muscular dystrophies, such as Duchenne's Muscular Dystrophy, Becker's Muscular Dystrophy, neuromuscular disorders and neurological disorders. This application also provides combination therapeutics, such as a biglycan therapeutic and a utrophin therapeutic.