Objective: To describe two cases of the rare action myoclonus renal failure syndrome.

Background: Action Myoclonus Renal Failure syndrome (AMRF) is characterized by neurological symptoms such as progressive action myoclonus epilepsy, dysarthria, ataxia, and generalized seizures. In addition, patients develop end-stage renal failure requiring dialysis and/or renal transplantation. The syndrome is considered to be an autosomal-recessive disease related to loss-of-function mutations in SCARB2 which encode a lysosomal-membrane type 2 protein, a member of the CD 36 scavenger receptor-like protein family. A total of 14 disease-causing SCARB2 mutations have been identified to date.

Results: Two female siblings are described. Their parents are consaguineous (first-degree cousins). Patient 1 started with a rapidly progressive nephrotic syndrome at the age of 17, becoming steroid-resistant and on hemodyalisis in few months. At age of 21, she developed action myoclonus of the inferior limbs, with subjective loss of strength and frequent falls. Later, she started having generalized tonic-clonic seizures. At 28 years old, she underwent renal transplantation. She died five years later due to complications associated with the renal graft and its treatment. The first complaint of patient 2 was difficulties climbing stairs at the age of 20. She then developed progressive gait ataxia and fatigue. At 25 years old, she had severe gait ataxia with frequent falls and marked action myoclonus. She became bedridden one year later. Cognitive function was preserved throughout the disease, with normal neuropsychological evaluation for both siblings. MRI showed mild cerebellar atrophy on patient 1 and no changes on patient 2. Electroencephalogram was compatible with progressive myoclonic epilepsy. Electromyography showed signs of demyelinating sensorimotor polyneuropathy.

Conclusions: We present two siblings with a rare mutation, causing action myoclonus with renal failure, myoclonic epilepsy and severe ataxia. These cases also support the demyelinating polyneuropathy as a feature of this syndrome. When the clinical findings are specific for AMRF and clinical suspicion is high, genetic testing can be a potential cost-effective diagnostic procedure.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/two-siblings-with-action-myoclonus-renal-failure-syndrome/