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

• Osteopetrosis
• Pyknodysostosis
• Hypoparathyroidism
• .

Kenny-Caffey syndrome is present at birth (congenital) and low birth weight may be one of the first symptoms. This extremely rare genetic disorder is characterized by abnormalities affecting the skeleton, the head, and the eyes. Recurrent episodes of unusually low levels of calcium (hypocalcemia) in the blood are common. Most affected individuals exhibit short stature of adult height ranging from 48 to 59 inches. Mental capacity is rarely affected.

Kenny-Caffey syndrome usually affects several bones of the body. Affected individuals may have thickened outer layers (cortexes) of various long bones, and abnormally thin marrow cavities (medullary stenosis). Some individuals may also have abnormal hardening of some bones (osteosclerosis).

Kenny-Caffey syndrome also affects the head and face. The anterior fontanel is a soft, membrane-covered area between the bones of an infant's skull that usually closes about 18 months after birth. However, in Kenny-Caffey syndrome, the anterior fontanel is abnormally large, closes late, and a fibrous joint between the bones in the forehead (metopic suture) is spaced wider than usual. As a result, affected infants have an abnormally large head circumference (macrocephaly) with a prominent forehead.

Several abnormalities of the eyes are also associated with Kenny-Caffey syndrome. Affected individuals may have unusually small eyes (microphthalmia), leakage of cerebrospinal fluid into the optic disk of the eye may cause swelling of the disk (papilledema), and/or farsightedness (hyperopia). In some cases of this disorder, nearsightedness (myopia) has been observed. One case reported in the medical literature noted retinal and corneal calcification. Another case had bilateral optic atrophy.

Episodes of abnormally low levels of calcium in the blood (hypocalcemia) are prevalent in individuals, especially infants, affected by Kenny-Caffey syndrome. Onset of hypocalcemia is usually within two to three months after birth. Other episodes may occur in relation to stress or may follow surgery or illness in an adult. Hypocalcemia is not permanent (transient) and may be caused by insufficient production of parathyroid hormones (hypoparathyroidism). These hormones, along with vitamin D and the hormone calcitonin, regulate the levels of calcium in the blood. The lack of the parathyroid hormones may be due to improper function or absence of the parathyroid glands in people with Kenny-Caffey syndrome. Symptoms of hypoparathyroidism include weakness; muscle cramps; excessive nervousness; loss of memory; headaches; and abnormal sensations such as tingling, burning, and numbness of the hands. (For more information about "Hypoparathyroidism," please see the Related Disorders section of this report.)

Low levels of calcium in the blood may also cause a condition called tetany, which is characterized by muscle cramps and periods of high-pitched respiration (stridor). Individuals with Kenny-Caffey syndrome may also exhibit abnormally low levels of phosphates in the blood (hypophosphatemia), low levels of a hormone that acts to reduce the blood level of calcium (calcitonin), low levels of circulating red blood cells (anemia), and seizures.

People affected by the recessive form of Kenny-Caffey syndrome have most of the above-mentioned abnormalities and symptoms. They may also exhibit liver disease during the first month of life (neonatal period), abnormally low levels of a certain type of white blood cell (neutropenia), improper function of another type of white blood cell (T-cells), and/or underdeveloped (hypoplastic), malformed nails.
.

Kenny-Caffey syndrome may be inherited as an autosomal recessive or dominant trait. X-linked recessive inheritance has not been ruled out. Genetic diseases are determined by two genes, one received from the father and one from the mother.

Dominant genetic disorders occur when only a single copy of an abnormal gene is necessary for the appearance of the disease. The abnormal gene can be inherited from either parent, or can be the result of a new mutation (gene change) in the affected individual. The risk of passing the abnormal gene from affected parent to offspring is 50% for each pregnancy regardless of the sex of the resulting child.

Recessive genetic disorders occur when an individual inherits the same abnormal gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk for two carrier parents to both pass the defective gene and, therefore, have an affected child is 25% with each pregnancy. The risk to have a child who is a carrier like the parents is 50% with each pregnancy. The chance for a child to receive normal genes from both parents and be genetically normal for that particular trait is 25%.

X-linked recessive genetic disorders are conditions caused by an abnormal gene on the X chromosome. Females have two X chromosomes but one of the X chromosomes is “turned off’ and all of the genes on that chromosome are inactivated. Females who have a disease gene present on one of their X chromosomes are carriers for that disorder. Carrier females usually do not display symptoms of the disorder because it is usually the X chromosome with the abnormal gene that is “turned off”. Males have one X chromosome and if they inherit an X chromosome that contains a disease gene, they will develop the disease. Males with X-linked disorders pass the disease gene to all of their daughters, who will be carriers. Males can not pass an X-linked gene to their sons because males always pass their Y chromosome instead of their X chromosome to male offspring. Female carriers of an X-linked disorder have a 25% chance with each pregnancy to have a carrier daughter like themselves, a 25% chance to have a non-carrier daughter, a 25% to have a son affected with the disease, and a 25% chance to have an unaffected son.

Investigators have determined that the recessive form of Kenny-Caffey syndrome may be caused by disruption or changes (mutations) of the tubulin-specific chaperone E (TBCE) gene located on the long arm (q) of chromosome 1 (1q42-q43). Chromosomes, which are present in the nucleus of human cells, carry the genetic information for each individual. Pairs of human chromosomes are numbered from 1 through 22, and an additional 23rd pair of sex chromosomes which include one X and one Y chromosome in males and two X chromosomes in females. Each chromosome has a short arm designated "p" and a long arm designated "q". Chromosomes are further sub-divided into many bands that are numbered. For example, "chromosome 1q42" refers to band 42 on the long arm of chromosome 1. The numbered bands specify the location of the thousands of genes that are present on each chromosome.

Some cases of autosomal recessive Kenny-Caffey syndrome have had parents who were related by blood (consanguineous). All individuals carry 4-5 abnormal genes. Parents who are close relatives (consanguineous) have a higher chance than unrelated parents to both carry the same abnormal gene, which increases the risk to have children with a recessive genetic disorder.
.

Kenny-Caffey syndrome is an extremely rare skeletal disorder that affects males and females in equal numbers. Fewer than 60 cases have been reported in the medical literature. Onset of hypocalcemia is usually within two to three months of life; the hypocalcemia is not permanent (transient). In an adult, episodes of hypocalcemia may be due to stress or follow surgery or illness. Kenny-Caffey syndrome was first described in the medical literature in 1966.
.

Symptoms of the following disorders can be similar to those of Kenny-Caffey syndrome. Comparisons may be useful for a differential diagnosis:

Hypoparathyroidism-retardation-dysmophic (HRD) syndrome, which is also known as Sanjad-Sakati syndrome, is an extremely rare disorder characterized by hypoparathyroidism that is present at birth (congenital); growth retardation, mental retardation; and characteristic facial abnormalities. Such facial features may include deep-set eyes, abnormally thin upper lip, abnormally small jaw (micrognathia), and a depressed bridge of the nose. Affected individuals may also have skeletal defects, abnormally thin marrow cavities (medullary stenosis), and abnormally low levels of calcium in the blood (hypocalcemia). HRD syndrome is inherited as an autosomal recessive trait. As with some cases of autosomal recessive Kenny-Caffey syndrome, HRD syndrome is caused by mutations of the TBCE gene meaning the two disorders caused by different mutations of the same gene (allelic disorders). Some researchers believe that the two disorders may be different expressions of the same disorder.

Osteopetrosis is a rare genetic skeletal disorder characterized by the abnormal hardening of bones. Symptoms may include thickening of the bones, increased density of the bone marrow, delayed closure of a soft spot of an infant's skull (anterior fontanel), and anemia. The basic defect in bone growth involves insufficient production of intercellular bone tissue by cells called osteoblasts. These osteoblasts aid in the production of bone by maintaining a balance between formation and loss of calcium in the bone. Osteopetrosis can be inherited as either an autosomal dominant or recessive trait. (For more information on this disorder, choose "Osteopetrosis" as your search term in the Rare Disease Database.)

Pyknodysostosis is a rare disorder characterized by short stature and increased density of the bones. Individuals with this disorder typically have short arms and legs with broad hands and feet. Delayed closure of the space between the bones of the skull (fontanels) typically occurs. Additional features may include an unusually large head (macrocephaly) with a small face, a receding chin with a small jaw, brittle finger and toe nails, a bluish discoloration of the whites of the eyes (blue sclerae), dental abnormalities, and/or an underdeveloped collarbone. Pyknodysostosis is inherited as an autosomal recessive trait. (For more information on this disorder, choose "Pyknodysostosis" as your search term in the Rare Disease Database.)

A large anterior fontanel that closes late is also seen in cleidocranial dysplasia and congenital hypoparathyroidism. (For more information on these disorders, choose "Cleidocranial Dysplasia" and "Hypoparathyroidism" as your search terms in the Rare Disease Database.)

The following disorder may be associated with Kenny-Caffey syndrome as a secondary characteristic. It is not necessary for a differential diagnosis:

Hypoparathyroidism is a rare endocrine disorder characterized by low levels of calcium in the blood. It is caused by insufficient production of parathyroid hormones. These hormones, along with vitamin D and the hormone calcitonin, regulate the levels of calcium in the blood. The lack of production of parathyroid hormones may be due to improper function or absence of the parathyroid glands. Symptoms of hypoparathyroidism include weakness; muscle cramps; excessive nervousness; loss of memory; headaches; and abnormal sensations such as tingling, burning, and numbness of the hands. The exact cause of hypoparathyroidism is not fully understood. (For more information on this disorder, choose "Hypoparathyroidism" as your search term in the Rare Disease Database.)
.

Diagnosis
The diagnosis of Kenny-Caffey syndrome may be confirmed by x-ray studies of the skeleton that reveal distinctive thickening of the outer layers (cortexes) of long bones along with unusually thin marrow cavities. Blood tests can detect episodes of low levels of calcium in the blood (hypocalcemia).

Treatment
The treatment of Kenny-Caffey syndrome is directed toward the specific symptoms that are apparent in each individual. Vitamin D and calcium have been prescribed for and proven effective in treating hypocalcemia. If anemia occurs, iron supplements may be prescribed. People with Kenny-Caffey syndrome should be monitored regularly by an eye doctor (ophthalmologist) who is familiar with the eye abnormalities associated with this syndrome.

Genetic counseling will be of benefit for affected individuals and their families. A supportive team approach for children with Kenny-Caffey syndrome may be of benefit. Such a team approach may include physical therapy and other medical, social, or vocational services. Other treatment is symptomatic and supportive.
.

Ongoing medical research is being conducted into the causes of and surgical treatment options for people with bone disorders.

Research on genetic disorders 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 and familial disorders in the future.
.

McKusick VA, ed. Online Mendelian Inheritance in Man (OMIM). Baltimore. MD: The Johns Hopkins University; Entry No:127000; Last Update:5/18/99. Entry No:244460; Last Update:5/18/99.

TEXTBOOKS
Gorlin RJ, et al., eds. Syndromes of the Head and Neck, 3rd ed. New York, NY: Oxford University Press; 1990:263-4.

Buyce ML, ed. Birth Defects Encyclopedia. Dover, MA: Blackwell Scientific Publications; For: The Center for Birth Defects Information Services Inc; 1990:1714-5.

Magalini SI, et al., eds. Dictionary of Medical Syndromes. 3rd ed.New York, NY: Lippincott Company; 1990:492.

Jones KL, ed. Smith's Recognizable Patterns of Human Malformation. 4th ed. Philadelphia, PA: W. B. Saunders Co: 1988:345.

REVIEW ARTICLES
Sabry MA, et al. Kenny-Caffey syndrome: an Arab variant? Clin Genet. 1999;55:44-49.

Janke EL, et al. Anaesthetic management of Kenny-Caffey syndrome using the laryngeal mask. Paediatr Anaesth. 1996;6:235-38.

Rebolleda FG, et al. Bilateral optic atrophy in Kenny’s syndrome. Acta Ophthalmol (Copenh). 1992;70:135-38.

Abdel-Al YK, et al. Kenny-Caffey syndrome. Case report and literature review. Clin Pediatr (Phila). 1989;28:175-79.

Lee WK, et al. The Kenny-Caffey syndrome: growth retardation and hypocalcemia in a young boy. Am J Med Genet. 1983;14:773-82.

JOURNAL ARTICLES
Parvari R, et al. Mutation of TBCE causes hypoparathyroidism-retardation-dysmorphism and autosomal recessive Kenny-Caffey syndrome. Nat Genet. 2002;32:448-52.

Diaz GA, et al. Sanjad-Sakati and autosomal recessive Kenny-Caffey syndromes are allelic: evidence for an ancestral founder mutation and locus refinement. Am J Med Genet. 1999;85:48-52.

Sabry MA, et al. Kenny-Caffey syndrome is part of the CATCH 22 haploinsufficiency cluster. J Med Genet. 1998;35:31-36.

Diaz GA, et al. The autosomal recessive Kenny-Caffey syndrome locus maps to chromosome 1q42-q43. Genomics. 1998;54:13-18.

Tahseen K, et al. Kenny-Caffey syndrome in six Bedouin sibships: autosomal recessive inheritance is confirmed. Am J Med Genet. 1997;69:126-32.


Franceschini P, et al. Kenny-Caffey syndrome in two sibs born to consanguineous parents: evidence for an autosomal recessive variant. Am J Med Genet. 1992;42:112-16.

Bergada I, et al. Kenny syndrome: description of additional abnormalities and molecular studies. Hum Genet. 1988;80:39-42.

Enriquez EJ, et al. Congenital medullary tubular stenosis. A case report of Caffey-Kenny syndrome. Acta Orthop Scand. 1988;59:326-27.

Fanconi S, et al. Kenny syndrome: evidence for idiopathic hypoparathyroidism in two patients and for abnormal parathyroid hormone in one. J Pediatr. 1986;109:469-75.

Majewski F, et al. The Kenny syndrome, a rare type of growth deficiency with tubular stenosis, transient hypoparathyroidism and anomalies of refraction. Eur J Pediatr. 1981;136:21-30.

Boynton JR, et al. Ocular findings in Kenny's syndrome. Arch Ophthalmol. 1979;97:896-900.