Definition:
Atypical late infantile CLN6 disease is part of a group of progressive degenerative neurometabolic disorders known as neuronal ceroid lipofuscinoses (NCLs). NCLs are characterized by an abnormal accumulation of lipopigaments, subtances combined of fats and proteins within the brain’s nerve cells, eyes, skin, muscle, and within other tissues throughout the body.

Although this disorder has clinical symptoms similar to other NCLs, it is distinct because its cause is known. The cause of a number of NCLs remains nebulous. Atypical late infantile CLN6 disorder is caused by a mutation on the CLN6 gene, which leads to an accumulation of transmembrane proteins in the cells. The gene CLN6 provides the code for a protein known as linclin, which plays an important role in the function of cellular membranes and in providing energy to nerve cells. This mutation essentially eliminates the function of the CLN6 gene and gives rise to the symptoms of this disorder. More than 18 mutations on the CLN6 gene have been identified. This condition causes nerve cells, found in the brain, retina, and in the central nervous system to die.

Atypical late infantile CLN6 predominately affects individuals of Portuguese, Indian, Pakistani, or Czech origin, although the exact prevalence figures are not known. It is estimated that the NCLs affect two to four of every 100,000 live births in the United States.

Symptoms:
Symptoms of Atypical late infantile CLN6 begin between 18 months to four years of age. Blindness, seizures, and loss of cognition are symptoms of this disorder. Loss of motor skills typically occurs between four and 10 years of age. As the disorder progresses, the individual affected becomes incapacitated.

Inheritance Pattern:
Atypical late infantile CLN6 is an autosomal recessive disorder.

Life Expectancy:
Life Expectancy for Atypical late infantile CLN6 is between 10 and 30 years of age.

Diagnosis and Testing:
A DNA analysis confirms a mutation on the CLN6 gene, hence a diagnosis of Atypical late infantile CLN6. For this analysis, blood or tissue sample is tested from individuals who are suspected of having the disorder and/or from members of families wherein a carrier of the CLN6 gene has been identified. Prenatal screening is also available.

Treatment:
There is no cure for Atypical late infantile CLN6. Treatment is limited to reducing or controlling the symptoms of this disorder. Neurologists are able to help control seizures or nervous system complications. An ophthalmologist can monitor vision loss, and physical and occupational therapists can assist the affected individual to maintain muscle movement and reduce muscle discomfort.

As the CLN6 gene has been mapped, genetic research is focused on yielding a greater understanding of the disorder’s mechanism and a discovery of therapies to prevent the loss of brain cells, a characteristic of this disorder.