Kenny-Caffey Syndrome (KCS)

At a glance

It is an extremely rare hereditary skeletal dysplasia presenting clinically in two different forms. In general terms, the Kenny-Caffey Syndrome is characterized by proportionate dwarfism as a result of thickening of the inner corticalis and stenosis of the medullary cavities of the tubular bones. The signs of the disease are present at birth. Other features include short stature, hypocalcemia, hypoparathyroidism, and normal intelligence. The onset of hypocalcemia is usually present within infancy, the first 2 to 3 months of life, and is transient. It is established that hypocalcemia in adult may be due to stress or follow surgery or illness.

Synonyms

Dwarfism-Congenital Medullary Stenosis Syndrome; Dwarfism-Tubular Bone Stenosis; Hypoparathyroidism-Retardation-Dysmorphism (HRD) Syndrome; Kenny Syndrome; Kenny-Linarelli Syndrome; Tubular Stenosis-Hypocalcemia-Convulsions-Dwarfism Syndrome; Tubular Stenosis-Periodic Hypocalcemia Syndrome; Tubular Stenosis with Hypocalcemia.

History

KCS2 was first described in the medical literature in 1966.

Classification

There are two clinical forms described for this medical condition:

• Kenny-Caffey Syndrome Type 1 (Hypoparathyroidism-Retardation-Dysmorphism [HRD] Syndrome, Sanjad-Sakati Syndrome): It is the recessive form of KCS and is an extremely rare disorder characterized by congenital hypoparathyroidism, growth retardation, intellectual disability, and severe facial abnormalities. The facial features include deep-set eyes, abnormally thin upper lip, micrognathia, and a depressed bridge of the nose. Affected individuals present medullary stenosis, and hypocalcemia. It is believed to be the result of mutations of the tubulin-specific chaperone E (TBCE) gene.

• Kenny-Caffey Syndrome Type 2 (KCS2): It is an extremely rare hereditary skeletal disorder characterized by medullary stenosis and craniocular abnormalities. The signs are present at birth and include short stature, normal intelligence, recurrent episode of hypocalcemia, and hypoparathyroidism. KCS2 is an autosomal dominant genetic disorder.

Incidence

Approximately 60 cases have been described in the medical literature. Both sexes are affected with equal severity.

Genetic inheritance

A genetic disorder caused by truncation mutations of the TBCE (tubulin-specific chaperone E) gene. It is an autosomal recessive trait which is reported almost exclusively in Middle Eastern populations. Autosomal dominant and X-linked transmission is also possible, especially in the KCS Type 2. Sporadic cases may be a result of new mutations. Genetic defect located on chromosome 1 (locus 1q42-q43).

Pathophysiology

The most striking biochemical finding is hypocalcemia, which is related to hypoparathyroidism in 46% of cases. The hypocalcemia is frequently associated with seizures or episodes of tetany. Thickening of long bone cortices and the calvaria of the skull are common findings. The cortical thickening is associated with medullary stenosis.

Diagnosis

Based on a constellation of clinical findings in addition to persistent hypocalcemia and low-to-normal parathyroid hormone assays. Growth hormone and thyroid hormone levels usually are normal. Anemia is present in 30% ...