Variable 'Faces' of Facioscapulohumeral Muscular Dystrophy

Abstract & Commentary

By Michael Rubin, MD, Professor of Clinical Neurology, Weill Cornell Medical College. Dr. Rubin reports no financial relationships relevant to this field of study.

Synopsis: With the advent of specific genetic tests, atypical forms of facioscapulohumeral muscular dystrophy can be reliably diagnosed.

Source: Hassan A, et al. Focal and other unusual presentations of facioscapulohumeral muscular dystrophy (FSHD). Muscle Nerve 2012; DOI: 10.1002/mus.23358.

Easily identified in its classic form, facioscapulohumeral muscular dystrophy (FSHD) usually begins in the second or third decade with facial weakness impairing eye closure, whistling, or smiling; shoulder girdle weakness with marked biceps and triceps atrophy; and scapular winging with accompanying foot drop in the scapuloperoneal variant. What are the uncommon phenotypes? How might they present?

Retrospective review of the Mayo Clinic electronic database between 1996-2011 disclosed 139 cases of FSHD, all of whom had been seen at least once in the Neuromuscular Clinic, of which seven were atypical, yet genetically confirmed. Encompassing four men and three women, ranging in age of onset from 18-63 years, the presenting symptom comprised monomelic leg or arm weakness, in three and two patients respectively, while two patients presented with axial weakness. One patient reported a post-traumatic onset of trapezius weakness, but a positive family history raised suspicions of a possible alternate diagnosis. Family history of FSHD was documented in only two, but all gave a history of having a "weak family member." Initial examination confirmed weakness in five patients. Concomitant peripheral neuropathy and dyspnea were seen in one patient each, and two patients had S1 radicular pain with gastrocnemius atrophy on presentation. Serum creatine kinase was normal in two, and at most thrice the upper limit of normal, while needle electromyography revealed myopathic changes consisting of low amplitude, short-duration, motor unit potentials with an early recruitment pattern, initially in all but two patients, but developing eventually in all. Atypical presenting features of FSHD should be expanded to include monomelic weakness, axial weakness, and dyspnea.

Commentary

With the advent of genetic testing for FSHD, the existence of atypical case presentations has been confirmed and includes FSHD with facial sparing, limb-girdle, or distal myopathy forms, or camptocormia (an abnormal posture with marked flexion of the thoracolumbar spine that abates when recumbent). Myoglobinuria is reported, but this patient had both a heterozygous mutation in calpain3 gene (CAPN3) exon 4, as well as an FSHD 4q35 deletion.1 Epilepsy, speech delay, and mental retardation were seperately seen as the presenting complaints of different individuals in a single family,2 and bilateral Coats' disease (idiopathic telangiectasia with intraretinal or subretinal exudation in the absence of retinal or vitreal traction) was reported in an aymptomatic 39 year-old woman.3 Muscle pain, tongue atrophy, hearing loss, and cardiomyopathy are also reported.

References

1. Pastorello E, et al. Atypical onset in a series of 122 cases with FacioScapuloHumeral Musculary Dystrophy. Clin Neurol Neursorg 2012;114:230-234.

2. Grosso S, et al. Epilepsy, speech delay, and mental retardation in facioscapulohumeral muscular dystrophy. Eur J Ped Neurol 2011;15:456-460.

3. Bass SJ, et al. Bilateral Coats' response in a female patient leads to diagnosis of facioscapulohumeral muscular dystrophy. Optometry 2011;82:72-76.