Lafora disease: diagnosis by skin biopsy

Lafora Disease: Report of a Rare Entity

Lafora disease is a rare, genetic, glycogen metabolism disorder inherited as autosomal recessive characterized by the presence of inclusion bodies, known as Lafora bodies, within the cytoplasm of the cells in the heart, liver, muscle, and skin. Lafora disease presents as a neurodegenerative disorder that causes impairment in the development of cerebral cortical neurons. We present here a case of Lafora disease that presented with progressive myoclonus epilepsy (PME) and investigated at our center. She was diagnosed to have Lafora disease with typical histological findings on skin biopsy and was found to be positive for the pathogenic mutation on genetic testing.

[Normal skin biopsy as a tool for extra-cutaneous disorders]

Biopsies of apparently healthy skin can contribute to the diagnosis of an internal disorder in a patient or in the detection of a potential disease carrier. Herein, we review those diseases for which dermatologists may be asked to perform a biopsy on normal skin where analysis by optical microscopy, immunofluorescence or electronic microscopy may result in diagnosis of an "internal" disease. Diseases for which biopsies are required for cell cultures (e.g. fibroblasts cultures), clonality testing or chromosomal analysis are not discussed here.

Progressive myoclonus epilepsy in a beagle

A nine-year-old, neutered female beagle was presented with a history of progressive myoclonic jerks. Clinical signs included mental depression and paroxysmal jerks of the head and forelimbs, apparently elicited by changes in light, noise or movements. Electroencephalographic findings were in accordance with myoclonus epilepsy. Postmortem histopathological findings included multiple periodic acid-Schiff-positive inclusion bodies throughout the central nervous system, but especially in the cerebellum, confirming the suspected diagnosis of Lafora's disease.

A unique carbohydrate binding domain targets the lafora disease phosphatase to glycogen

Lafora disease (progressive myoclonus epilepsy of Lafora type) is an autosomal recessive neurodegenerative disorder resulting from defects in the EPM2A gene. EPM2A encodes a 331-amino acid protein containing a carboxyl-terminal phosphatase catalytic domain. We demonstrate that the EPM2A gene product also contains an amino-terminal carbohydrate binding domain (CBD) and that the CBD is critical for association with glycogen both in vitro and in vivo. The CBD domain localizes the phosphatase to specific subcellular compartments that correspond to the expression pattern of glycogen processing enzyme, glycogen synthase. Mutations in the CBD result in mis-localization of the phosphatase and thereby suggest that the CBD targets laforin to intracellular glycogen particles where it is likely to function. Thus naturally occurring mutations within the CBD of laforin likely result in progressive myoclonus epilepsy due to mis-localization of phosphatase expression.