LEOPARD syndrome

Alternate names

Lentigines, Electrocardiographic conduction abnormalities, Ocular hypertelorism, Pulmonic stenosis, Abnormal genitalia, Retardation of growth, Deafnes; Multiple lentigines syndrome; Cardiomyopathic lentiginosis; Noonan syndrome with multiple lentigines

Definition

LEOPARD syndrome is an inherited condition characterized by abnormalities of the skin, heart, inner ears, and genitalia. The acronym LEOPARD describes the features of the syndrome: (L)entigines - dark spots on the skin (E)lectrocardiographic conduction defects - abnormalities of the electrical activity of the heart (O)cular hypertelorism - widely spaced eyes (P)ulmonary stenosis - obstruction of the normal outflow of blood from the right ventricle of the heart (A)bnormalities of the genitalia (R)etarded (slowed) growth resulting in short stature (D)eafness As the condition name suggests, Noonan syndrome with multiple lentigines is very similar to a condition called Noonan syndrome, and it can be difficult to tell the two disorders apart in early childhood. However, the features of these two conditions differ later in life.

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Epidemiology

Noonan syndrome with multiple lentigines is thought to be a rare condition; approximately 200 cases have been reported worldwide.

Cause

Mutations in one of several genes can cause Noonan syndrome with multiple lentigines. Approximately 85 percent of individuals with this condition have mutations in the PTPN11 gene. Another 10 percent have mutations in the RAF1 gene. In rare cases, mutations in the BRAF or MAP2K1 gene have been found to cause this condition. The remaining individuals with Noonan syndrome with multiple lentigines do not have an identified mutation in any of these four genes. In these individuals, the cause of the condition is unknown.

The PTPN11, RAF1, BRAF, and MAP2K1 genes all provide instructions for making proteins that are involved in important signaling pathways needed for the proper formation of several types of tissue during development. These proteins also play roles in the regulation of cell division, cell movement (migration), and cell differentiation (the process by which cells mature to carry out specific functions).

A mutation in the PTPN11, RAF1, BRAF, or MAP2K1 gene leads to the production of a protein that functions abnormally, which impairs the protein's ability to respond to cell signals. A disruption in the regulation of systems that control cell growth and division leads to the characteristic features of Noonan syndrome with multiple lentigines.

Types

There are 3 types of LEOPARD syndrome, which are distinguished by their genetic cause. Type 1 is caused by mutations in the PTPN11 gene; type 2 is caused by mutations in the RAF1 gene; and type 3 is caused by mutations in the BRAF gene.

Inheritance

Autosomal dominant pattern, a 50/50 chance.

This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.

Signs and symptoms

The characteristic features of Noonan syndrome with multiple lentigines include brown skin spots called lentigines that are similar to freckles, heart defects, widely spaced eyes (ocular hypertelorism), a sunken chest (pectus excavatum) or protruding chest (pectus carinatum), and short stature. These features vary, however, even among affected individuals in the same family. Not all individuals with Noonan syndrome with multiple lentigines have all the characteristic features of this condition.

The lentigines seen in Noonan syndrome with multiple lentigines typically first appear in mid-childhood, mostly on the face, neck, and upper body. Affected individuals may have thousands of small dark brown skin spots by the time they reach puberty. Unlike freckles, the appearance of lentigines has nothing to do with sun exposure. In addition to lentigines, people with this condition may have lighter brown skin spots called café-au-lait spots. Café-au-lait spots tend to develop before the lentigines, appearing within the first year of life in most affected people.

Of the people with Noonan syndrome with multiple lentigines who have heart defects, about 80 percent have hypertrophic cardiomyopathy, which is a thickening of the heart muscle that forces the heart to work harder to pump blood. The hypertrophic cardiomyopathy most often affects the lower left chamber of the heart (the left ventricle). Up to 20 percent of people with Noonan syndrome with multiple lentigines who have heart problems have a narrowing of the artery from the heart to the lungs (pulmonary stenosis).

People with Noonan syndrome with multiple lentigines can have a distinctive facial appearance. In addition to ocular hypertelorism, affected individuals may have droopy eyelids (ptosis), thick lips, and low-set ears. Affected individuals also usually have an abnormal appearance of the chest; they either have pectus excavatum or pectus carinatum.

At birth, people with Noonan syndrome with multiple lentigines are typically of normal weight and height, but in some, growth slows over time. This slow growth results in affected individuals being shorter than average, although less than half of people with Noonan syndrome with multiple lentigines have significantly short stature.

Other signs and symptoms of Noonan syndrome with multiple lentigines include hearing loss caused by abnormalities in the inner ear (sensorineural deafness), mild intellectual disability, and extra folds of skin on the back of the neck. Affected males often have genital abnormalities, which can include undescended testes (cryptorchidism) and a urethra that opens on the underside of the penis (hypospadias). These abnormalities may reduce the ability to have biological children (decreased fertility). Females with Noonan syndrome with multiple lentigines may have poorly developed ovaries and delayed puberty.

Noonan syndrome with multiple lentigines is one of a group of related conditions collectively known as RASopathies. These conditions all have similar signs and symptoms and are caused by changes in the same cell signaling pathway. In addition to Noonan syndrome with multiple lentigines, the RASopathies include Noonan syndrome, cardiofaciocutaneous syndrome, Costello syndrome, neurofibromatosis type 1, and Legius syndrome.

Diagnosis

Noonan syndrome with multiple lentigines (NSML) should be suspected in individuals with one or more of the following cardinal features:

• Lentigines
• Cardiac abnormalities, particularly hypertrophic cardiomyopathy
• Poor linear growth/short stature
• Pectus deformity
• Dysmorphic facial features, including widely spaced eyes and ptosis

Additional features occurring frequently in NSML:

• Variable degree of cognitive deficits
• Sensorineural hearing loss
• Cryptorchidism
• Skeletal anomalies
• Café au lait macules

Establishing the Diagnosis The diagnosis of Noonan syndrome with multiple lentigines is established either clinically in a proband with the following clinical findings or, if clinical findings are insufficient, by identification of a heterozygous pathogenic variant in one of four genes (PTPN11, RAF1, BRAF, and MAP2K1) by molecular genetic testing.

Treatment

Treatment of cardiovascular anomalies and cryptorchidism is usually the same as in the general population.

Treatment of hearing loss may include the following:

• Fitting with appropriate hearing aids
• Enrollment in an appropriate educational program for the hearing impaired
• Consideration for cochlear implantation, a promising habilitation option for persons with profound deafness
• Recognition that, as distinct from many clinical conditions, the management and treatment of severe-to-profound congenital deafness involves primarily the social welfare and educational systems rather than the medical care system .

Any developmental disability should be addressed by early intervention programs and individualized education strategies. Treatment of cryptorchidism in males is usually the same as in the general population.

NIH genetic and rare disease info

• NIH info on LEOPARD syndrome

LEOPARD syndrome is a rare disease.

LEOPARD syndrome Resources
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