Lafora Disease is reported in Beagles, Miniature wire Haired Dachsunds, Bassets and People. It is caused by a defect in the gene EPM2A which codes for glycogen phosphatase laforin or the EPM2B gene coding for Ubiquitin E3 ligase Malin. In dogs, the defect is in the EPM2B gene and there is a massive expansion of the gene with multiple repeats of part of it. This leads to loss of function of the gene resulting in an excessive accumulation of glycogen with certain cells and this is converted into an insoluble substance called polyglucosan. Gradual precipitation of this in neurons is called Lafora Bodies –named for their appearance microscopically. This leads to a neurodegenerative disease initially showing myoclonus-twitching and jerking movements. These progress to tonic-clonic seizures.
Affected patients may show other signs such as transient blindness, visual hallucinations (sudden unexplained fear response), and photo-convulsions (flashing light or sunlight affects them). It is hard to diagnose in the live patient as blood, urinalysis and CSF analysis is normal. EEG measurements may register spikes and some show abnormal EMG as well. MRI may show cortical atrophy as well. Most cases are diagnosed post mortem or can now be tested for DNA.
The gene is hard to analyse since it is the result of an expansion of one section and this makes distinguishing between the carrier and affected difficult. In simple terms, the dogs carrying the gene show “more” of this section and deciding if it is a small amount more ie only one faulty copy and a carrier or lots “more” of this section and therefore carrying two faulty copies is not so easy. At the moment only a small number of Labs feel confident with doing the testing.
Treatment of this disease is hard as it is a cumulative problem. Some success has been found using the drug Levetiracetam to reduce myoclonic jerks and a low carbohydrate diet to reduce glycogen production. Doggles may be used in patients with light-sensitive clinical signs. Ultimately sadly most patients progress and are euthanized due to worsening symptoms.
Most of the current publications involved the MWD and a good paper is at this link. However there is a recent publication in beagles.
A list of tested beagles can be found here.