These cancers are associated with the synaptic proteins amphiphysin and gephyrin. Paraneoplastic SPS with amphiphysin antibodies and breast adenocarcinoma tend to occur together. These patients tend not to have GAD antibodies. Passive transfer of the disease by plasma injection has been shown in paraneoplastic SPS but not classical SPS.There is evidence of genetic risk of SPS. The HLA class II locus makes patients susceptible to the condition. Most SPS patients have the DQB1* 0201 allele. This allele is also associated with type 1 diabetes. Diagnosis
SPS is diagnosed by evaluating clinical findings and excluding other conditions. There is no specific laboratory test that confirms its presence. Underdiagnosis and misdiagnosis are common.The presence of antibodies against GAD is the best indication of the condition that can be detected by blood and cerebrospinal fluid (CSF) testing. Anti-GAD65 is found in about 80 percent of SPS patients. Anti-thyroid, anti-intrinsic factor, anti-nuclear, anti-RNP, and anti-gliadin are also often present in blood tests. Electromyography (EMG) demonstrates involuntary motor unit firing in SPS patients. EMG can confirm the diagnosis by noting spasms in distant muscles as a result of subnoxious stimulation of cutaneous or mixed nerves. Responsiveness to diazepam helps confirm that the patient has SPS, as this decreases stiffness and motor unit potential firing.The same general criteria are used to diagnose paraneoplastic SPS as the normal form of the condition. Once SPS is diagnosed, poor response to conventional therapies and the presence of cancer indicate that it may be paraneoplastic.
Furthermore, recent studies have also implied the proteins role in cathepsin D deficiency; the overexpression of the defective protein appears to have significant effects on cathepsin D processing, with implications suggesting that accumulation of ATP synthase subunit C would result. Only recently have studies of human patients shown deficiency of lysosomal aspartyl proteinase cathepsin D.

Adult dominant form
Between 1.3 and 10% of cases are of the adult form. The age at onset is variable (6–62 yr). Two main clinical subtypes have been described: progressive myoclonus epilepsy (type A) and dementia with motor disturbances, such as cerebellar, extrapyramidal signs and dyskinesia (type B). Unlike the other NCLs, retinal degeneration is absent. Pathologically, the ceroid-lipofuscin accumulates mainly in neurons and contains subunit C of the mitochondrial ATP synthase.Two independent families have been shown to have mutations in the DNAJC5 gene – one with a transversion and the other with a deletion mutation. The mutations occur in a cysteine-string domain, which is required for membrane targeting/binding, palmitoylation, and oligomerization of the encoded protein cysteine-string protein alpha (CSPα). The mutations dramatically decrease the affinity of CSPα for the membrane. A second report has also located this disease to this gene. Treatment
Currently, no widely accepted treatment can cure, slow down, or halt the symptoms in the great majority of patients with NCL, but seizures may be controlled or reduced with use of antiepileptic drugs. Additionally, physical, speech, and occupational therapies may help affected patients retain functioning for as long as possible. Several experimental treatments are under investigation.