449 - Newly Diagnosed Progressive Muscular Atrophy in a 46-year-old Landscaper

Case Diagnosis: Progressive Muscular Atrophy presenting with progressive isolated lower motor neuron signs in a 46-year-old male.

Case Description: A 46-year-old male presented with a 5-month history of progressive weakness, fasciculations, and muscular atrophy. The weakness began in his left hand and progressed proximally to affect the entire left arm, then similarly affected his right arm, impairing ADLs like feeding himself and brushing his teeth. He later experienced neck weakness with head drop and dysphonia. Physical exam showed normal sensation throughout, decreased bulk, profound upper extremity weakness, minor lower extremity weakness, 2- to 2+ DTRs, and negative Hoffmann/Babinski/Jaw jerk reflexes. MRI of the brain and cervical spine, along with extensive lab tests, were unremarkable. EMG/NCS of LUE and LLE was consistent with diffuse motor neuron disease.

Discussions: This patient’s presentation was consistent with the diagnosis of Progressive Muscular Atrophy (PMA). PMA is a diffuse motor neuron disease with isolated lower motor neuron (LMN) signs such as weakness, atrophy, and fasciculations, as well as electrodiagnostic evidence of LMN dysfunction in 2+ myotomes. It is a neurodegenerative condition on the Amyotrophic Lateral Sclerosis (ALS) spectrum of disease. It is speculated that PMA may in fact be ALS with subclinical upper motor neuron (UMN) involvement, and PMA meets criteria for the diagnosis of ALS using the 2019 Gold Coast Criteria. The treatment of PMA is non-curative and includes multidisciplinary measures to improve quality of life and maintain independence.

Conclusions: This case highlights the importance of considering a diagnosis of PMA in a patient presenting with progressive weakness without evidence of sensory or UMN involvement. PMA may be a subtype of ALS, has no known cure, and treatment is supportive.