We present two cases of primary neck extensor weakness and fatty replacement of paraspinal muscles on MRI who were found to have pathogenic variants in two genes associated with different muscular dystrophies.

Neck extensor weakness is an uncommon presentation of neuromuscular disease, and the established etiologies can include various muscular dystrophies. Calpain pathogenic variants (CAPN3) commonly cause limb-girdle muscular dystrophy (LGMD) and are mainly due to homozygous or compound heterozygous variants, although a heterozygous cause of myopathy has been identified. Lamin A/C heterozygous or homozygous variants (LMNA) can cause multiple phenotypes including LGMD1B and Emery-Dreifuss Muscular Dystrophy (EGMD).

Patient 1 is a 77 year old woman with over 20 years of isolated progressive head drop and camptocormia, with MRI findings of paraspinal atrophy and fatty replacement, who was found to have a heterozygous nonsense pathogenic variant c.1079G>A (p.W360X) in CAPN3. Creatine Kinase (CK) was within normal range. Patient 2 is a 35 year old woman with multifocal findings including neck weakness with MRI findings of paraspinal atrophy and fatty replacement, who was found to have a heterozygous missense pathogenic variant c.1622G>A (p.R541H) in LMNA. CK was slightly high (241, ULN=140). In both patients EMG/NCS showed abnormal spontaneous activity in the paraspinal muscles, and patient 2 had myopathic changes seen in the deltoids.

Here we report two patients with neck extensor weakness, paraspinal atrophy with fatty replacement, and EMG evidence of abnormal spontaneous activity in the paraspinal muscles, who were found to have pathogenic variants in two different genes associated with muscular dystrophy. Further investigation including muscle biopsy with targeted staining is planned to better understand the pathogenicity of these variants.