Terminology for Congenital Absence of Fingers
The medical term for the absence of one or more fingers is "limb deficiency" or "digital deficiency," with specific subtypes including ectrodactyly (split hand deformity), oligodactyly (fewer than five fingers), and transverse terminal defects depending on the pattern and level of absence. 1
Primary Terminology
Limb deficiency is the broad medical term encompassing all congenital or acquired absences of extremity structures, occurring at a rate of 5-6 per 10,000 live births. 1
Specific Anatomic Classifications:
Transverse terminal defects: The most common subtype (50% of all limb deficiencies), characterized by absence of distal structures with intact proximal segments, where the axis of deficiency is perpendicular to the extremity. 1
Digital deficiencies: Approximately 50% of transverse defects are digital, specifically involving absence of parts of one or more fingers or toes. 1
Ectrodactyly (also called "split hand deformity" or "lobster claw anomaly"): Characterized by absence of digits ranging from single finger absence to complete split hand/foot deformity. 2, 3
Oligodactyly: Defined as the presence of fewer than five fingers on a hand, one of the rarest congenital anomalies of upper extremities. 4
Pathophysiologic Mechanism
The underlying cause is hypothesized to be vascular disruption during embryonic limb formation or in already-formed fetal limbs. 1, 2
- The timing of vascular disruption correlates directly with severity: earlier disruptions (before 68 days' gestation) cause more severe proximal defects and orofacial involvement, while later disruptions (≥70 days' gestation) result in isolated digital deficiencies. 1, 2
Associated Conditions to Evaluate
When encountering digital absence, evaluate for:
Isolated defects versus syndromic presentations (Williams Syndrome, 22q11.2 Deletion Syndrome, Simpson-Golabi-Behmel Syndrome, Fetal Alcohol Syndrome). 5
Oromandibular-limb hypogenesis (hypoglossia/hypodactyly): Rare combination of transverse limb deficiencies with tongue/lower jaw absence or hypoplasia, occurring at 1 per 200,000 births. 1
Associated hand abnormalities: Syndactyly (most common associated finding), clinodactyly, camptodactyly, symphalangism, or hypertrophied adjacent metacarpals. 4
Clinical Pitfalls
Do not confuse with amniotic band syndrome, which was the most common incorrect diagnosis made by clinicians in surveillance studies. 6
Central digit hypoplasia presents distinctly with hypoplasia of thumb and fifth finger with soft tissue nubbins replacing fingers 2-4 at the metacarpal-phalangeal joint level—this differs from terminal transverse defects ending at the wrist. 6
Symbrachydactyly involves hypoplastic middle and distal phalanges with syndactyly, not complete absence. 7, 6
Diagnostic Approach
Physical examination should document which specific rays are missing and their level of absence using standardized alphanumeric documentation (R for radial, C for central, U for ulnar with numbers 1-5). 8
Radiographic evaluation to assess carpal and metacarpal bone abnormalities, which help determine whether missing digits are ulnar-sided, central, or combined patterns. 4
Genetic testing (chromosomal microarray, targeted FISH, or whole exome sequencing) when digital abnormalities occur with dysmorphic features, developmental delay, or other congenital anomalies. 5
Cardiac evaluation is essential as multiple genetic syndromes with digital abnormalities have associated cardiac defects. 5