Information on the following diseases can be found in the Related Disorders section of this report:

• Sirenomelia Sequence

Caudal Regression Syndrome is characterized by abnormal development of the tail (caudal) end region of the developing fetus. Abnormalities associated with this disorder may include partial absence of the tailbone (Coccyx) end of the spine which usually causes no symptoms, and/or a wide range of developmental abnormalities predominantly involving the lower portion of the body.

Patients with Caudal Regression Syndrome may have some of the following symptoms: absence or underdevelopment of the lower vertebrae, pelvis and/or tailbone at the end of the spine; paralysis or numbness of the legs; an difficulty in controlling bowel movements and urination; dislocation of the hip; joints in a permanently fixed position; underdeveloped muscles; abnormal growth of the thighbone; a clubfoot; intestines that are twisted; defects of the anal and urinary systems; multiple cysts or partial fusion of the kidneys; swelling of the pelvis due to a blockage in the urinary system; displacement of the external sex organs; and/or a defect in which the urinary opening is on the underside of the penis (hypospadias).

Less common abnormalities found in some patients with Caudal Regression Syndrome may be: an abnormal amount of spinal fluid in the head (hydrocephaly); partial or complete absence of the gland that supplies hormones (pituitary gland); cleft palate or lip; an underdeveloped or small lower jaw; a downward displacement of the tongue; defects of the heart; and/or more than the normal number of fingers and/or toes.

The exact cause of Caudal Regression Syndrome is not known in most cases. Nearly sixteen percent of the patients afflicted with this disorder have had mothers that were diabetic. Autosomal dominant inheritance has been suggested in some cases. Human traits, including the classic genetic diseases, are the product of the interaction of two genes, one received from the father and one from the mother. In dominant disorders, a single copy of the disease gene (received from either the mother or father) will be expressed "dominating" the other normal gene and resulting in the appearance of the disease. The risk of transmitting the disorder from affected parent to offspring is 50 percent for each pregnancy regardless of the sex of the resulting child.

Caudal Regression Syndrome is a rare disorder that affects males and females in equal numbers. It is estimated that Causal Regression Syndrome will appear in about 3 of each 100,000 live births.

Symptoms of the following disorders can be similar to those of Caudal Regression Syndrome. Comparisons may be useful for a differential diagnosis:

Sirenomelia Sequence is a rare disorder characterized by irregular development of the lower limbs. The deformity is present at birth, usually as a single lower extremity or as two legs that are joined together. Accompanying malformations of the spine and skeletal system, with vertebrae either absent or defective, commonly occur. (For more information on this disorder, choose "Sirenomelia Sequence " as your search term in the Rare Disease Database.)

Caudal Regression Syndrome can be detected in a fetus during the second trimester of pregnancy by ultrasound.

Orthopedic devices may be used to help problems of the hip, back and legs.

Problems such as an imperforate anus, hydrocephaly, cleft palate or lip, and extra fingers or toes can be improved or corrected with surgery.

Genetic counseling may be of benefit for patients and their families. Other treatment is symptomatic and supportive.

Research on birth defects and their causes is ongoing. The National Institutes of Health (NIH) is sponsoring the Human Genome Project which is aimed at mapping every gene in the human body and learning why they sometimes malfunction. It is hoped that this new knowledge will lead to prevention and treatment of genetic disorders in the future.

TEXTBOOKS
McCusick VA., ed. Online Mendelian Inheritance in Man (OMIM). Baltimore, MD: The Johns Hopkins Press; Entry No: 600145; Created 10/12/94; Last Edit Date:12/18/96.

Jones KL., ed. Smith's Recognizable Patterns of Human Malformation. 5th ed. Philadelphia, A: W.B. Saunders Co; 1997:635.

Buyse ML., ed. Birth Defects Encyclopedia. Dover, MA: Blackwell Scientific Publications; For: Center for Birth Defects Information Services Inc;1990:296-7.

JOURNAL ARTICLES
Bohring A, et al., Polytopic anomalies with agenesis of the lower vertebral column. Am J Med Genet. 1999;87:99-114.

Fukada Y, et al., Caudal regression syndrome detected in a fetus with increased nuchal translucency. Acta Obstet Gynecol Scand. 1999;78:655-56.

Hirano H, et al., Caudal regression syndrome: MR appearance. Comput Med Imaging Graph. 1998;22:73-76.

Cama A, et al., Multidisciplinary management of caudal regression syndrome (26 cases). Eur J Pediatr Surg. 1996;6 Suppl 1:44-45.

Nguyen BD, et al., Bone scintigraphy of caudal regression syndrome. Clin Nucl Med. 1996;21:802-04.

PARTIAL TRANSPOSITION OF THE PENIS AND SCROTUM WITH ANTERIOR URETHRAL DIVERTICULUM IN A CHILD BORN WITH THE CAUDAL REGRESSION SYNDROME: A.M. Shanberg, et al.; J Urol (October, 1989, issue 424. Pp. 1060-2.