In some cases, for example, if a physician suspects the person may have a myopathy rather than ALS, a muscle biopsy may be performed.A number of infectious diseases can sometimes cause ALS-like symptoms, including human immunodeficiency virus (HIV), human T-lymphotropic virus (HTLV), Lyme disease, and syphilis. Neurological disorders such as multiple sclerosis, post-polio syndrome, multifocal motor neuropathy, CIDP, spinal muscular atrophy, and spinal and bulbar muscular atrophy can also mimic certain aspects of the disease and should be considered.ALS must be differentiated from the "ALS mimic syndromes", which are unrelated disorders that may have a similar presentation and clinical features to ALS or its variants. Because the prognosis of ALS and closely related subtypes of motor neurone disease are generally poor, neurologists may carry out investigations to evaluate and exclude other diagnostic possibilities. Disorders of the neuromuscular junction, such as myasthenia gravis (MG) and Lambert–Eaton myasthenic syndrome, may also mimic ALS, although this rarely presents diagnostic difficulty over time. Benign fasciculation syndrome and cramp fasciculation syndrome may also, occasionally,  mimic some of the early symptoms of ALS. Nonetheless, the absence of other neurological features that develop inexorably with ALS means that, over time, the distinction will not present any difficulty to the experienced neurologist; where doubt remains, EMG may be helpful.Most cases of ALS, however, are correctly diagnosed, with the error rate of diagnosis in large ALS clinics being less than 10%.
Acroosteolysis is resorption of the distal bony phalanges. Acroosteolysis has two patterns of resorption in adults:  diffuse and bandlike. The diffuse pattern of resorption has a widely diverse differential diagnosis which includes:  pyknodysostosis, collagen vascular disease and vasculitis, Raynauds neuropathy, trauma, epidermolysis bullosa, psoriasis, frostbite, sarcoidosis, hypertrophic osteoarthropathy, acromegaly, and advanced leprosy.The bandlike pattern of resorption may be seen with polyvinyl chloride exposure and Hadju-Cheney syndrome.A mnemonic commonly used for acro-osteolysis is PINCHFO.Pyknodysostosis, Psoriasis,
Injury (thermal burn, frostbite),
Neuropathy (diabetes),
Collagen vascular disease (scleroderma, Raynauds),
Hyperparathyroidism,
Familial (Hadju-Cheney, progeria), 
Occupational (polyvinyl exposure),
Acroosteolysis may be associated with minimal skin changes or with ischemic skin lesions that may result in digital necrosis. : 665

See also
Nail anatomy


== References ==