Arthrogryposis, distal, type 2B3 is a condition that primarily affects the musculoskeletal system, leading to joint contractures and alterations in limb function. It is classified among the distal arthrogryposes, where congenital joint stiffness predominantly influences the hands and feet. Variants in the MYH3 gene have been implicated in this condition, and it follows an autosomal dominant pattern of inheritance, meaning that a single altered copy of the gene can be associated with the phenotype. Prevalence data are not specified, and although this condition is present from birth, the clinical features may vary considerably in severity among affected individuals.

Individuals affected by arthrogryposis, distal, type 2B3 typically exhibit distinctive physical features that form the core clinical presentation. Characteristic findings include downslanted palpebral fissures, adducted thumbs, camptodactyly, ulnar deviation of the hand, and a narrow mouth, all of which are noted to be present in 100% of reported cases. These features often contribute to the diagnosis during infancy as parents and clinicians notice challenges related to joint mobility and facial configuration. While these particular signs are always observed, the impact on overall function and appearance can vary, and not all individuals experience every possible complication associated with the condition. In addition, severity and the degree of impairment may differ from one affected person to another, emphasizing that there is a broad spectrum of clinical expression.

The underlying cause of arthrogryposis, distal, type 2B3 is linked to variants in the MYH3 gene. The protein encoded by MYH3 plays an important role in muscle development and function during embryonic growth, and disruptions in this protein can affect the formation and mobility of the limbs. Inherited in an autosomal dominant pattern, a single altered copy of the gene is enough to lead to the condition. That, even among relatives who inherit an affected gene, the specific symptoms and severity can vary considerably, a phenomenon known as variable expressivity. Families are encouraged to consider genetic counseling to better understand the inheritance implications and to discuss how the condition may impact future family planning. Associated genes include MYH3.