Pathophysiology of Rett Syndrome
Children are lovable! It is pleasing to play with them and talk to them. But have you come across any child who repeatedly squeezes/rubs/claps/flaps their hands most of the time so much so that it appears a little irky. This child might be a suffering from Rett Syndrome.
Let’s decipher how Rett Syndrome occurs.
Rett Syndrome named after Sir Andreas Rett, is a neurodevelopmental disorder associated with regression of milestones acquired in early life.
To understand the pathophysiology of Rett syndrome we need to understand a little about a gene called MECP2 which codes for a protein MECP2. MECP2 stands for Methyl CpG binding Protein – 2. This protein has a unique methyl CpG binding domain which binds to regions containing 5 methyl-Cytosine and causes transcription or repression of the specific DNA region. It is found in high quantity in neurons and is associated with normal functioning of CNS and synaptic contact formation.
The problem starts with a inactivating mutation in MECP2 gene which follows a X linked Dominance pattern of inheritance. Although it is not clear how these inactivating mutations of MECP2 cause Rett syndrome but it has been proposed that MECP2 mutations affect the neuronal maturation in the following ways –
- Delayed synaptic maturation : failure of arborization formation in the cortex leads to abnormal signaling and abnormal development of Autonomic nervous system along with motor and cortical tissues and glial tissues. This explains why children with rett syndrome have postnatal deceleration in head growth.
- Disruption of Cholesterol metabolism leads to abnormal neuronal development.
Pathophysiology behind stereotypy of hand movements in Rett Syndrome
Rett Syndrome is characterized by stereotypy of hand movements such as wringing, tapping, licking, washing. These non purposeful movements are a result of loss of normal acquired purposeful movements of hands which get replaced by stereotypical movements.