<unk>  is caused by mutations in the HSPG2 gene, which makes the protein perlecan, which is found in muscle and cartilage. Relationships between the disease and perlecan deficiency have been studied. In<unk> , it is suspected that abnormal perlecan function leads to a deficiency in acetylcholinesterase, an enzyme involved in breaking down the neurotransmitter acetylcholine, which incites muscle contraction. If acetylcholine is not broken down, it can lead to prolonged muscle contraction/stiffening of the muscles (myotonia).
Schwartz–Jampel syndrome
Hagemoser–Weinstein–Bresnick syndrome
Kasabach–Merritt syndrome
Schwartz–Matsuo syndrome
Bare lymphocyte syndrome type II
Smith–Fineman–Myers syndrome
Aarskog–Scott syndrome
Pitt–Hopkins syndrome