Isolated paraspinal myopathy: a distinct subtype of facioscapulohumeral muscular dystrophy

Fascioscapulhumeral muscular dystrophy (FSHD) is inherited as an autosomal dominant trait and is characterized by facial and shoulder girdle weakness usually appearing in adolescence. In milder cases signs may be apparent not before late adulthood. A scapuloperoneal subtype sparing the facial muscles has been described. We present two cases with genetically confirmed FSHD with a distinct phenotype solely affecting the paraspinal muscles.

Case reports: Patient 1 was a 65-year-old man with a more than 15 year history of a slowly progressive bent spine syndrome. Prior to admission the patient had multiple orthopedic diagnostic procedures and treatments. He had normal strength of the upper and lower extremities and no facial weakness. Patient 2 was a 60-year-old healthy man presenting with a short history of lower back pain. He was referred to our hospital because of an MRI study of the lumbar spine revealing no disc herniation but marked atrophy of the paraspinal muscles. Family history was negative in both cases with respect to neuromuscular disorders. EMG studies of both patients revealed normal findings of the muscles of upper and lower extremities but marked myopathic changes in the paraspinal muscles. Laboratory examinations showed slightly elevated CPK levels (200–300 U/l) in patient 1

and 2.

In both patients DNA testing revealed restriction fragments consistent with a 3 kb deletion at the D4Z4 locus (FSHD-repeat) on chromosome 4q35. The fragment sizes of the D4Z4 locus varies in the population between 40–320 kb. Only fragments <38kb (EcoRI-digestion) and <35 kb (EcoRI+Bln I, double digestion), respectively, are diagnostic for FSHD. The size of the smaller fragments following EcoRI and double digestion was 33–30 kb in both Patients.

Conclusions: i) Patients with the FSHD on chromosome 4q35 may present with a phenotype of isolated paraspinal mypoathy. ii) In cases with paraspinal muscular atrophy in MRI and/or bent spine syndrome an underlying FSHD should be considered.