Seckel Syndrome and Primordial Dwarfism

Seckel syndrome is an inherited form of primordial dwarfism, meaning that an infant starts out very small and fails to grow normally after birth. While persons with Seckel syndrome will typically be proportionate in scale, they will have distinctively small head size. Intellectual and developmental disabilities are also common.

Despite an array of physical and mental challenges facing a person with Seckel syndrome, many have been known to live well in excess of 50 years.

Causes

Seckel syndrome is an inherited disorder linked to genetic mutations on one of three different chromosomes. It is considered extremely rare with little more than 100 cases reported since 1960. Many children diagnosed with Seckel syndrome were born to parents who are closely related (consanguineous), such as with first cousins or siblings.

Seckel syndrome is a recessive genetic disorder, meaning that it occurs only when a child inherits the same abnormal gene from each parent. If the child receives one normal gene and one abnormal gene, the child will be a carrier of the syndrome but will not usually show symptoms.

If both parents have the same chromosomal mutation for Seckel syndrome, their risk of having a baby with Seckel syndrome is 25 percent, while the risk of having a carrier is 50 percent.

Characteristics

Seckel syndrome is characterized by abnormally slow fetal development and low birth weight. Following birth, the child will experience slow growth and bone maturation resulting in short yet proportional stature (as opposed to short-limbed dwarfism, or achondroplasia). Persons with Seckel syndrome have distinct physical and developmental characteristics, including:

• Very small size and weight at birth (average 3.3 pounds)
• Extremely small, proportionate stature
• Abnormally small head size (microcephaly)
• A beak-like protrusion of the nose
• Narrow face
• Malformed ears
• Unusually small jaw (micrognathia)
• Intellectual disability, often severe with an IQ less than 50

Other symptoms may include abnormally large eyes, a high arched palate, tooth malformation, and other bone deformities. Blood disorders such as anemia (low red blood cells), pancytopenia (not enough blood cells), or acute myeloid leukemia (a type of blood cancer) are also commonly seen.

In some cases, the testes in men will fail to descend into the scrotum, while women may have an abnormally enlarged clitoris. In addition, people with Seckel syndrome may have excessive body hair and a single, deep crease across the palms of their hands (known as a simian crease).

Diagnosis

Diagnosis of Seckel syndrome is based almost exclusively on physical symptoms. X-rays and other imagining tools (MRI, CT scan) may be needed to distinguish it from other similar conditions. There is currently no lab or genetic test specific to Seckel syndrome. In some cases, a definitive diagnosis cannot be made until the child gets older and the characteristic symptoms appear.

Treatment and Management

Treatment of Seckel syndrome is focused on any medical problem that may arise, especially blood disorders and structural deformities. Mentally challenged individuals and their families will need to be given appropriate social support and counseling services.