Brachydactyly type B is a rare genetic condition that affects the normal development of fingers and toes. It is congenital. This article provides an overview of brachydactyly type B, covering its characteristics, genetic origins, diagnosis, and management.
Understanding Brachydactyly Type B
Brachydactyly type B is characterized by the incomplete development or complete absence of the outermost bones of the fingers and toes, known as the distal phalanges. This often affects the index through little fingers, while the thumbs are intact but may appear flattened, split, or duplicated. The feet are similarly affected, though to a lesser degree than the hands.
Individuals with brachydactyly type B often experience a complete absence of fingernails on the affected digits. Other features include hypoplasia of the middle phalanges and sometimes webbed fingers (syndactyly). The digits on the thumb side of the hand are less severely affected compared to those on the pinky finger side.
Genetic Basis and Inheritance
The cause of brachydactyly type B is a mutation in the ROR2 gene. This gene provides instructions for making a protein involved in cell growth and differentiation, processes important for proper bone development. When the ROR2 gene is altered, it disrupts these processes, leading to the characteristic skeletal abnormalities.
Brachydactyly type B is inherited in an autosomal dominant pattern. This means a person needs to inherit only one copy of the altered ROR2 gene from either parent to develop the condition. If one parent has brachydactyly type B, there is a 50% chance that each child will inherit the altered gene and the condition. The condition can also arise from a new, spontaneous gene mutation in an individual with no family history.
Diagnosis and Related Health Considerations
Brachydactyly type B is identified at birth through a physical examination, where characteristic digital abnormalities are visible. Diagnosis is confirmed with X-rays, which visualize bone structure and determine the extent of skeletal changes in the fingers and toes. Genetic testing provides definitive confirmation by identifying the specific mutation in the ROR2 gene.
While brachydactyly type B primarily affects the digits, some individuals may have other associated health considerations. These can include additional skeletal abnormalities beyond the hands and feet, such as fusion of wrist or ankle bones, or shortening of the hand or foot bones that connect to the digits. Healthcare providers assess for any broader systemic impacts to ensure comprehensive care.
Management and Living with the Condition
Management approaches for brachydactyly type B focus on improving hand and foot function and addressing cosmetic concerns. Occupational and physical therapy are recommended to enhance dexterity and range of motion in the affected digits. These therapies help individuals develop adaptive strategies for daily tasks and improve overall limb usage.
In some cases, surgical interventions may be considered to correct deformities or improve functionality. Surgical options involve separating webbed fingers, reconstructing missing bone segments, or addressing other structural issues to enhance the limb’s form and function. Beyond physical treatments, addressing the psychological and social aspects of living with a visible condition is also important. Support networks provide valuable resources and help individuals develop coping mechanisms and adaptation strategies for navigating social interactions and personal well-being.