TYPES
Joubert Syndrome (JS) is a genetically and clinically heterogeneous disorder, meaning that it can be caused by mutations in different genes and present with varying clinical features. As a result, different types or subtypes of Joubert Syndrome have been identified based on the specific genetic mutations involved. Here are some of the commonly recognized types of Joubert Syndrome:
1. Joubert Syndrome Type 1 (JBTS1): This is the most common and well-characterized type of Joubert Syndrome. It is caused by mutations in the gene known as INPP5E.
2. Joubert Syndrome Type 2 (JBTS2): Mutations in the TMEM216 gene are responsible for causing JBTS2. This type is associated with a milder form of Joubert Syndrome and may have a better prognosis compared to other types.
3. Joubert Syndrome Type 3 (JBTS3): Mutations in the AHI1 gene are associated with JBTS3. This type is often characterized by more severe neurological symptoms, including intellectual disability and kidney abnormalities.
4. Joubert Syndrome Type 4 (JBTS4): Mutations in the NPHP1 gene are responsible for causing JBTS4. This type is often associated with kidney and eye abnormalities, as well as intellectual disability.
5. Joubert Syndrome Type 5 (JBTS5): JBTS5 is caused by mutations in the CEP290 gene. This type is often characterized by kidney, eye, and liver abnormalities, as well as intellectual disability.
6. Joubert Syndrome Type 6 (JBTS6): Mutations in the TMEM67 gene are responsible for JBTS6. This type is often associated with the characteristic molar tooth sign on brain imaging, as well as kidney and liver abnormalities.
7. Joubert Syndrome Type 7 (JBTS7): Mutations in the RPGRIP1L gene are associated with JBTS7. This type is often characterized by eye abnormalities, including retinal dystrophy.
SYMPTOMS
Joubert Syndrome (JS) can present with a wide range of symptoms, and the severity and combination of symptoms can vary among individuals. Some of the common symptoms associated with Joubert Syndrome include:
1. Cerebellar abnormalities: Joubert Syndrome is primarily characterized by cerebellar vermis hypoplasia, which refers to underdevelopment or absence of the cerebellar vermis. This can lead to motor difficulties, including poor coordination, balance issues, and difficulties with fine motor skills.
2. Respiratory abnormalities: Many individuals with Joubert Syndrome have abnormal breathing patterns, such as episodes of rapid breathing (hyperpnea) and/or periods of interrupted breathing (apnea). These breathing irregularities may occur especially during sleep.
3. Eye movement abnormalities: Eye movement abnormalities are common in Joubert Syndrome and may include abnormal jerking eye movements (nystagmus) and impaired ability to coordinate eye movements (oculomotor apraxia).
4. Intellectual and developmental disabilities: Intellectual disability is often observed in individuals with Joubert Syndrome, ranging from mild to severe. Developmental delays are also common, including delays in speech and language acquisition.
5. Kidney and liver abnormalities: Approximately 30-50% of individuals with Joubert Syndrome may have kidney abnormalities, such as cysts or structural abnormalities. Liver abnormalities, including fibrosis or enlargement, may also be present in some cases.
6. Facial features: Some individuals with Joubert Syndrome may have distinctive facial features, including a prominent forehead, deep-set eyes, and a broad nasal bridge.
7. Low muscle tone (hypotonia): Hypotonia, or decreased muscle tone, is often observed in individuals with Joubert Syndrome. This can contribute to difficulties with motor skills and coordination.
8. Additional features: Other features that may be present in some individuals with Joubert Syndrome include extra fingers or toes (polydactyly), tongue abnormalities, seizures, and hearing loss.