The great majority of congenital deformities arise between the fourth and eighth weeks of pregnancy. Birth defects are typically classified as structural or developmental, causing mild to severe impairments. Approximately 3% of newborns in the United States are affected with major structural or genetic birth defects.1 According to the Centers for Disease Control and Prevention (CDC), each year about 1500 US babies are born with upper limb reductions (about 4 of every 10,000 babies) and about 750 are born with lower limb reductions (about 2 of every 10,000 babies).2 A missing or incomplete arm at birth is referred to as congenital upper limb deficiency or congenital limb amputation or limb reduction. These defects are mostly attributed to primary intrauterine growth inhibition or disruptions secondary to intrauterine destruction of normal embryonic tissues.
There are several classification systems for congenital deformities of the upper limbs such as anatomic or topographical, embryologic, teratologic sequencing, genetic, and different combinations of these. The limb deficiency disorders are a broad group of congenital anomalies featuring significant hypoplasia or aplasia of 1 or more bones of the limbs that can occur in isolation or associated with other anomalies.3
Limb deficiencies can be longitudinal or transverse. Longitudinal deficiencies are along the long axis of the limb (complete or partial absence of the radius, ulna, fibula, or tibia), and mostly genetic or teratogenic in origin. In a transverse deficiency, all the elements below a certain level in the patient’s arm are missing (loss of forearm, hand) and the limb structures before the point of the defect remain intact. It is mostly caused by early amnion rupture sequence (amniotic band).3 The arm appears similar to that of an amputation stump, which is sometimes known as “congenital amputation.” Terms used may be aphalangia (missing fingers and phalanges) to amelia (absence of limb).4,5
Baby R was born full term to a G2 P1 mother via repeat cesarean delivery at 39 weeks’ gestation. There is no consanguinity with the parents, and the mother was compliant for all prenatal care visits. The mother was negative for hepatitis A, B, and C, human immunodeficiency virus (HIV), and Group B Streptococcus (GBS). Delivery was uncomplicated, but after the delivery of the head and upper body it was noted that Baby R had an absent left forearm, despite a reported “normal” prenatal ultrasound at 20 weeks’ gestation. A diagnosis of amniotic band disruption was made by the neonatologist and explained to the parents, who were distraught. The APGAR scores were 8 at 1 minute and 9 at 5 minutes. Baby R had no other physical abnormalities, no cardiac murmur, and no dysmorphic features. He had an uneventful nursery course and was discharged home with his mother on day 3 of life.
Baby R was followed in the pediatric primary care office for routine newborn care and was seen by the pediatric nurse practitioner (PNP) at the 2-month health promotion visit. Physical assessment revealed normal growth patterns, and he was feeding well. Physical exam was unremarkable with the exception of the left forearm. A small paddle of nubbins was noted at the tip of the deformity above the elbow of the left upper extremity. The infant had fleeting movements of the extremity from the shoulder with poor control. The right upper extremity appeared normal with a full shoulder, elbow, wrist, and digital range of motion, with a normal complement of digits.
Abnormalities of the limbs originate in different stages of embryonic development. Limb buds first appear as small elevations of the ventrolateral body during the fourth week of gestation. At the tip of each limb bud, the ectoderm (outermost layer of cells and tissue in embryonic development) becomes thickened to form an apical ectodermal ridge. Interaction between this ridge and the mesenchymal cells, which become connective tissue, is essential to limb development.6 The apical ectodermal ridge has an influence on the connective tissue, which promotes growth and development of the limbs, and is essential for the elongation process. Defects such as this occur early in gestation as osteogenesis of the long bones starts in the seventh week.
As with other congenital birth defects, the exact cause of an upper limb deficiency is typically not known. Some research has suggested that the exposure of the mother during pregnancy to various viruses, chemicals, medications, and tobacco smoke can be contributing factors.7 Amniotic band syndrome is caused from rupture to the amniotic sac, which can cause various abnormalities. It is due to constriction of encircling amniotic bands, and often can affect the limbs, face, joints, abdomen, or chest wall, and cause neural tube defects.8,9 This infant was referred to the regional Shriners Hospital where he was diagnosed at age 4 months with left upper extremity transverse deficiency at the level of the distal humerus, and not an amniotic band. The orthopedist reported the defect for Baby R was the result of a failure of the ectodermal ridge functioning, most likely from vascular compromise of unknown origin.
When a child is born with a congenital limb deficiency, it affects not only the child, but also parents and families. Parents experience grief and loss with the birth of a child with any deformity and they need guidance and support from the healthcare providers, families, and friends. In a 16-year prospective study of prenatal diagnosis of fetal malformation, the authors report the proportion of limb defects diagnosed via ultrasound was low; wherein 3 of 4 babies with a limb deficiency were not diagnosed in utero.10
Parents of children born with (unexpected) limb deficiency are often shocked and have feelings of guilt. The mother tries to think back if she did any anything wrong that contributed to the defect. The parents may overprotect the child and treat him/her differently from other children because of guilt, which could be detrimental to the growth and development of the child. If parents are not adjusting to the diagnosis, it will affect how the child will feel and react to his/her body.
1. Centers for Disease Control and Prevention. Update on overall prevalence of major birth defects--Atlanta, Georgia, 1978-2005. MMWR Morb Mortal Wkly Rep. 2008;57(1):1-5. Available at: https://www.cdc.gov/mmwr/preview/mmwrhtml/mm5701a2.htm. Accessed February 21, 2019.
2. Centers for Disease Control and Prevention. Birth defects: Upper and lower limb reduction defects. Available at: https://www.cdc.gov/ncbddd/birthdefects/ul-limbreductiondefects.html. Updated April 20, 2018. Accessed February 21, 2019.
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