Fig. 9

Facioscapulohumeral Muscular Dystrophy diagnostic diagram (Lamperti et al. 2010; Ricci et al. 2016; Mul 2022; Pasnoor and Dimachkie 2019). Facioscapulohumeral Muscular Dystrophy is clinically characterized by the triad of: facial weakness, scapular winging, and asymmetric limb muscle weakness. Facial weakness may manifest as transverse smile, sleeping with the eyes partially opened, inability to pucker, whistle, or drink from a straw. Palpebral ptosis and extraocular muscles are usually spared; this is important clue for the differential diagnosis with mitochondrial myopathies, as ophthalmoparesis is a cardinal feature of the Mitochondrial myopathy of the subtype Progressive External Ophthalmoplegia. Scapular winging is caused by weakness of the serratus anterior and trapezius muscles with inability to lift the arms, combined with wasting of the triceps brachialis, and biceps brachialis muscles, resulting in “Popeye” arms (reference to the cartoon character) with sparing of the forearm muscles. The diagnosis is confirmed by molecular studies and muscle biopsy is usually not performed, except in rare cases for differential diagnosis. D4Z4: macrosatellite (large tandem repeat) in the subtelomeric region of chromosome 4q35 (that contains the DUX4 gene); DUX4 gene: double homeobox 4 gene; FSHD1: Facioscapulohumeral Muscular Dystrophy type 1. Neurological physical examination grading by MRC (Medical Research Council): 1 Trace contraction of the muscle; 2 Ability to move with gravity eliminated; 3 Active movement against gravity; 4 Ability to move the joint against combination of gravity, and some resistance; and 5 Normal power