As of 2020, early evidence indicates that a third cause of FSHD2 is mutation in both copies of the LRIF1 gene, which encodes the protein ligand-dependent nuclear receptor-interacting factor 1 (LRIF1). LRIF1 is known to interact with the SMCHD1 protein. As of 2019, there are presumably additional mutations at other unidentified genetic locations that can cause FSHD2.Mutation of a single allele of SMCHD1 or DNMT3B can cause disease. Mutation of both copies LRIF1 has been tentatively shown to cause disease in a single person as of 2020. As in FSHD1, a 4qA allele must be present for disease to result. However, unlike the D4Z4 array, the genes implicated in FSHD2 are not in proximity with the 4qA allele, and so they are inherited independently from the 4qA allele, resulting in a digenic inheritance pattern. For example, one parent without FSHD can pass on an SMCHD1 mutation, and the other parent, also without FSHD, can pass on a 4qA allele, bearing a child with FSHD2. Two ends of a disease spectrum
Initially, FSHD1 and FSHD2 were described as two separate genetic causes of the same disease. However, they can also be viewed not as distinct causes, but rather as risk factors.
Society and culture
Media
In the Amazon Video series The Man in the High Castle, Obergruppenführer John Smiths son, Thomas, is diagnosed with Landouzy-Dejerine syndrome. In the biography Stuart: A Life Backwards, the protagonist was affected by muscular dystrophy, presumably FSHD. Patient and research organizations
The FSHD Society (named "FSH Society" until 2019) was founded in 1991 on the East Coast by two individuals with FSHD, Daniel Perez and Stephen Jacobsen. The FSHD Society claims to have advocated for the standardization of the disease name facioscapulohumeral muscular dystrophy and its abbreviation FSHD. The FSHD Society claims to have raised funding for seed grants for FSHD research and co-wrote the MD-CARE Act of 2001, which provided federal funding for all muscular dystrophies. The FSHD Society has grown into the worlds largest grassroots organization advocating for patient education and scientific and medical research for FSHD. One notable spokesperson for FSHD Society has been Max Adler, an actor on the TV series Glee. Friends of FSH Research is a research-oriented nonprofit organization founded in 2004 by Terry and Rick Colella from Kirkland, Washington after their son was diagnosed with FSHD. The FSHD Global Research Foundation was founded in 2007 by Bill Moss in Australia, a former Macquarie Bank executive affected by FSHD. It is currently directed by Mosss daughter. It was named Australian charity of the year for 2017. It is the largest funder of FSHD medical research outside of the United States as of 2018. FSHD EUROPE was founded in 2010.