Congenital absence of both forearm and hand, unilateral is a developmental defect observed at birth that affects the upper extremity, specifically the forearm and hand on one side. The condition is recognized by a transverse absence of the radius, ulna, and all distal elements forming the hand, with either the left or right side being involved. The precise genetic basis is not yet established and its occurrence appears sporadic, with reliable prevalence estimates not available at this time. This anomaly is typically identified during the early neonatal period through physical examination and imaging studies.

The hallmark feature of this condition is the unilateral absence of the forearm and hand, where the limb terminates abruptly with missing bones and soft tissues that normally constitute the upper extremity. It is usually noted at birth during routine physical examinations or prenatal imaging, leading to a clear clinical diagnosis. Not all individuals experience additional complications beyond the limb absence, and severity as well as functional impact can vary considerably.

The precise genetic basis of congenital absence of both forearm and hand, unilateral is not well established, and no specific gene has been linked to its occurrence. It is generally thought to result from complex developmental factors during embryogenesis rather than from a clearly defined inherited mutation. Because there is no known inheritance pattern with this condition, it is usually considered an isolated event. Genetic counseling may be considered if there are concerns about recurrence or if additional anomalies are present.