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limb deficiency defects

Monday 16 October 2006

LDD

Limb deficiency defects (LDD) have a overall birth prevalence of LD was 1 in 1,816.

32% of LDD children had structural malformations in other systems. Two main forms of classification were used: morphologic and causal.

Additional malformations were most commonly seen in infants with amelia, rudimentary limb (RL), radial/tibial (RT), intercalary or central axis (CA) LD and rarely in those with terminal transverse (TT) or ulnar/fibular (UF) defects.

Upper limbs (81%) are involved significantly more often than lower limbs (42%) and there are more right-sided defects (83% vs. 71%) due to an excess of right arm involvement especially with radial ray and split hand anomalies.

Single limb involvement is relatively common with amelia (88%), UF (82%), RT (50%), and TT (50%) defects.

With other LD, multimelic involvement is more characteristic. This was usually symmetric with intercalary and RL defects but asymmetric with CA anomalies and digital deficiencies (DD).

ETiology

- 17% of cases have genetic disorders
- 52% have recognized associations, anomalies, sequences, environmental causes or patterns of unknown origin
- 31% have unknown patterns of malformations.

The commonest entities were amnion disruption sequence (16% of cases) and VACTERL association (8%).

Both of these disorders show unusual temporal distribution. Patterns of malformations differed with the type of LD. Amelia and digital amputations were often seen with body wall defects, atypical anencephaly or encephalocele, and cleft lip reflecting amnion disruption.

Rudimentary limb is seen with anencephaly, omphalocele, renal agenesis, aberrant genitalia, and imperforate anus, reflecting defects of blastogenesis including the cloacal exstrophy and caudal regression sequences and Schisis association.

Radial/tibial defects are associated with different patterns depending on whether the limb defects are unilateral or bilateral.

Unilateral defects occurr with anomalies suggesting VACTERL association or the facio-auriculo-vertebral anomaly, while bilateral defects occurred more often in genetic or potentially genetic disorders including VACTERL with hydrocephalus.

Central axis defects showed three main patterns of association: one reflecting the ectrodactyly-ectodermal dysplasia-clefting syndrome; one with tongue anomalies representing a variant of oro-mandibular-limb (Hanhart) anomaly, and the last with hydronephrosis indicating a group of "acro-renal" syndromes.

Strong associations with other anomalies are not seen in the groups with TT, UF, or intercalary defects.

Etiology

- terotogen exposure

  • teratogen drugs
    • thalidomid

- chorionic villus sampling (CVS)
- amniotic band sequence
- vascular accident
- chromosomal anomalies

  • 2q31 anomalies
  • 6q21 anomalies
  • 7q21-q22 anomalies
  • 4q anomalies

See also

- limb malformations

References

- Evans JA, Vitez M, Czeizel A. Congenital abnormalities associated with limb deficiency defects: a population study based on cases from the Hungarian Congenital Malformation Registry (1975-1984). Am J Med Genet. 1994 Jan 1;49(1):52-66. PMID: 8172251