[Parkinson-dementia and amyotrophic lateral sclerosis association (complex of Guam). Diagnostic challenge, Mexican patient].

Background: The Amyotrophic Lateral Sclerosis-Parkinsonism-Dementia Complex (ALS-PDC) was first described in the islands of Guam. This pathology presented its peak incidence in the 1950s. Due to the rarity of the association, we report a clinical case with this complex. The objective was to describe the nosological and pathogenic implications of these neurodegenerative disorder, since they are not frequent to find in our population. Clinical case: We present a case of Latinoamerican origin who initially manifested systemic symptoms of more than 6 years of evolution, with subsequent cognitive alterations. Later, patient began with gait disturbances and motor symptoms suggestive of parkinsonism with atypical data and data of motor neurone disease (MND). More studies were carried out and confirmed findings compatible with upper and lower motor neuron involvement. A mutation in the POLG gene was observed, related to mitochondrial depletion syndrome. Conclusion: Despite the knowledge of this association, it is an entity whose clinical diagnosis could be very difficult to achieve. In addition, molecular mechanisms have not been fully identified, the most common genes related to Parkinsonism and ALS have been excluded, and even attempts to locate the locus were made, without achieving accurate results. Unfortunately, being a neurodegenerative disease, the prognosis is fatal, with no disease-modifying treatment.