There are far more conditions that mimic ALS than you can imagine: at least 22.

“Potentially curative treatments exist for certain ALS mimic syndromes,” states a report in the Iranian Journal of Neurology (April 2016), “but delay in starting these therapies may have an unfavorable effect on outcome.”

ALS Mimic Syndrome
ALS mimic syndrome refers to a group of medical conditions whose clinical presentation resembles those of ALS in the latter’s early stages.

The IJN points out that there have been only a few studies published regarding ALS mimic syndrome.

According to population based studies, nearly 10 percent of people diagnosed with ALS have actually had a different medical condition.

Diseases that Mimic ALS and
Their ALS-Like Symptoms

• Adrenomyeloneuropathy – lower leg stiffness and partial paralysis

• Adult polyglucosan body disease – progressive muscle weakness and stiffness

• Allgrove AAA syndrome – atrophy, muscle weakness, movement problems

• B12 deficiency – muscle weakness, problems with walking

• Benign monomelic amyotrophy – atrophy and weakness of one limb; fasciculations; possibly reduced reflexes

• Celiac disease – atrophy, weakness, fasciculations

• Creutzfeldt-Jakob disease – atrophy, fasciculations

• Inclusion body myositis – asymmetric weakness, difficulty swallowing

• Isaac’s disease – atrophy, weakness, fasciculations, diminished reflexes

• Isolated neck extensor myopathy – weak neck muscles

• Kennedy’s disease – atrophy and weakness of facial, bulbar and limb girdle muscles; tremor; fasciculations near the mouth

• Lyme disease – weakness, fasciculations

• Mitochondrial disorder – atrophy, weakness, fasciculations

• Multifocal motor neuropathy with conduction block – focal weakness; fasciculations

• Multiple sclerosis – limb weakness, unsteady gait, slurred speech

• Myasthenia gravis – muscle weakness, trouble chewing and swallowing

• Oculopharyngeal muscular dystrophy – bulbar weakness

• Overactive thyroid – weakness, fasciculations

• Paraneoplastic encephalomyelitis – unsteady gait leading to paralysis; slurred speech; trouble swallowing

• Post-polio syndrome – atrophy, weakness, problems swallowing

• Syringomyelia – atrophy and weakness

• Transthyretin familial amyloid neuropathy – tongue atrophy and fasciculations

Considerations
All of the aforementioned conditions present with at least one symptom that is seen with ALS.

Some of the conditions eventually present with symptoms totally unrelated to neuromuscular function, and in other cases may present with those symptoms right from the get-go. So nothing’s engraved in stone here; variability is high.

The mimicking nature of these disorders is apparent mostly in their early stages before the more non-relevant symptoms start popping up such as bowel and bladder dysfunction, rapid heart rate, vision problems and cognitive impairment, to name a few.

As mentioned, there’s much variation involved. For instance, in oculopharyngeal muscular dystrophy, the eyelids are usually affected – but in ALS they are not.

But there are cases of oculopharyngeal muscular dystrophy in which eyelid involvement is minimal, and most of the weakness is seen in the bulbar region, making this disease a potential mimicker of bulbar-onset ALS.

Another consideration is that the more progressed the above disorders become, the less they resemble ALS, especially ALS in its early stages.

The longer the time lapse, the more apparent the differences become in symptoms and clinical presentation.

  • For example, some of the diseases have a very slow progression.
  • Another example is benign monomelic amyotrophy: The pathology remains in just one limb.

Benign fasciculation syndrome mimics ALS more so in the petrified mind of the patient rather than to the neurologist.

The Iranian Journal of Neurology goes on to point out that fasciculations with motor neuron disease are asymptomatic and that the patient is unaware of them until the physician detects them.

“They are diffuse and rarely are the presenting symptom,” states the paper.

“Muscle fasciculation without weakness should be considered a benign phenomenon,” continues the Journal, “although follow-up (sometimes 6 months or more), might be required to confirm benign nature of that.”

Sources
ncbi.nlm.nih.gov/pmc/articles/PMC4912674/ ghr.nlm.nih.gov/condition/adult-polyglucosan-body-disease
rarediseases.info.nih.gov/diseases/457/triple-a-syndrome
webmd.com/diet/vitamin-b12-deficiency-symptoms-causes#2-6
jnnp.bmj.com/content/75/suppl_2/ii43
rarediseases.info.nih.gov/diseases/6793/isaacs-syndrome
tandfonline.com/doi/abs/10.3109/21678421.2014.980614
mayoclinic.org/diseases-conditions/post-polio-syndrome/symptoms-causes/dxc-20314513
ncbi.nlm.nih.gov/pmc/articles/PMC4746052/
pdfs.semanticscholar.org/7f32/c57551bfb64dc687c96ee1ca0302cac7541c.pdf
jmedicalcasereports.biomedcentral.com/articles/10.1186/1752-1947-7-218
mayoclinic.org/diseases-conditions/multiple-sclerosis/symptoms-causes/dxc-20131884
lymedisease.org/lyme-basics/lyme-disease/about-lyme/
mayoclinic.org/diseases-conditions/myasthenia-gravis/symptoms-causes/dxc-20200262 diseases that mimic als