Table 1.

Joint Genetic Diseases

Location	Gene locus	Inheritance	Phenotype	Clinical Synopsis (skeletal)
17q22	Noggin	Autosomal dominant	Proximal symphalangism 1A	Joint fusion Proximal interphalangeal joint synostoses Distal interphalangeal joint synostoses (occasional) Carpal and tarsal bone fusion
20q11.22	Gdf5, CDMP1, SYNS2, OS5,BDA1C, SYM1b	Autosomal dominant	Proximal symphalangism 1B	Joint fusion Distal interphalangeal joint fusions Flat feet Absence of the cuboid bone Bone fusion (proximal/middle phalanges)
3p24.1	Tgfbr2		Loeys-Dietz syndrome type 2 (formerly, Marfan syndrome type 2)	Joint laxity Osteoporosis (some patients) Low-impact fractures Arachnodactyly Camptodactyly Brachydactyly Contractures
1p13-p11	Notch2	Autosomal dominant	Hajdu-Cheney syndrome	Joint laxity Short stature Osteopenia Osteoporosis Pathologic fractures Acroosteolysis
8q12.1	Jaws/Impad1	Autosomal recessive	Chondrodysplasia with joint dislocations, GRAPP type	Joint dislocations Shortening and deformity of the limbs Brachydactyly Longitudinal splitting of the proximal phalanx of forefinger Splitting of the first metacarpal in two parts Short stature
8q24.11	Ext1	Autosomal dominant	Multiple cartilaginous exostoses, type 1	Cartilaginous protuberances at ends of long bones Short metacarpal Exostoses in juxtaepiphyseal regions of long bones Genu valgum Madelung-like forearm deformities Bilateral overriding of single toes
3q13.33	Hgd	Autosomal recessive	Alkaptonuria (AKU)	Ochronotic pigmentation of connective tissue Ochronotic arthritis Ochronotic arthropathy Chronic joint pain Degeneration of intervertebral disks Fusion of vertebral bodies