Metachromatic leukodystrophy. Late childhood and pre-adolescence forms (late onset).. Arylsulfatase A (ASA) deficiency.
Incidence
AR disease.
Clinical Characteristics
In this condition, the symptoms start between three and twelve years of age and the first symptoms are progressive difficulties with walking and evidence of pyramidal signs and involvement of the peripheral nerves, with depressed tendon reflexes and/or slow nerve conduction velocities. There may be an early period when only polyneuropathy is observed. The spinal fluid may be elevated. Mental deterioration may be evident immediately or later after the onset of the motor signs. Some cases show atypical signs such as onset of hemiplegia, cerebellar signs, dystonia and choreoatetosis. In these cases, nerve conduction velocity and CSF protein may be normal or less evident. Behavioral changes and cognitive deficits are common and may be striking. Seizures may occur but are rare. The course of the disease is somewhat longer than in the late infantile form. Diagnosis is similar to the late infantile form. Enzyme deficiency of arylsulfatase A (ASA) in leukocytes and cultured fibroblasts is observed as well as excessive sulfatiduria, which is constant. In some cases, ASA activity is normal in patients with abnormal amount of sulfatides in the urine and intralysosomal deposits in Shwann cells. These cases may have a deficiency of the activator protein SAP1 which can be demonstrated in leukocytes and cultured fibroblast.
Precipitants
no
Provocation Tests
no
Diagnostic Procedures
EB-W, EB-F. Diagnosis is similar to the late infantile form. Enzyme deficiency of arylsulfatase A (ASA) in leukocytes and cultured fibroblasts is observed as well as excessive sulfatiduria, which is constant. In some cases, ASA activity is normal in patients with abnormal amount of sulfatides in the urine and intralysosomal deposits in Shwann cells. These cases may have a deficiency of the activator protein SAP1 which can be demonstrated in leukocytes and cultured fibroblasts.