Symptoms of Autonomic Neuropathy May Suggest Diagnosis of Primary Amyloidosis

Iqra Mumal, MSc avatar

by Iqra Mumal, MSc |

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rare mutation in FAP

Researchers presented the main features of primary amyloidosis, showing the need for careful diagnosis in patients that present with neuropathic symptoms, especially autonomic neuropathy, to correctly identify other conditions such as familial amyloid neuropathy (FAP).

The study, titled “Autonomic Neuropathy and Albuminocytologic Dissociation in Cerebrospinal Fluid As the Presenting Features of Primary Amyloidosis: A Case Report,” was published in the journal Frontiers in Neurology.

Autonomic neuropathy refers to a set of symptoms that occur when nerves that manage regular activities such as blood pressure, heart rate, sweating, bowel and bladder emptying, and digestion, are damaged. Neuropathies occur in 35 percent of cases with amyloidosis, but only 7.5 percent of patients present with neuropathy-associated symptoms.

If a patient presents with neuropathy with autonomic failure and end organ involvement (damage occurring in major organs fed by the circulatory system), the symptoms suggest a diagnosis of primary amyloidosis.

The general symptoms of primary amyloidosis include diarrhea, weight loss, and general autonomic failure, but these symptoms can often be misdiagnosed as diabetic neuropathy or CIDP (chronic inflammatory demyelinating polyneuropathy).

There are many different diseases that could contribute to autonomic neuropathy, such as diabetic autonomic neuropathy, amyloid neuropathy, acute and subacute autonomic neuropathies, immune-mediated and paraneoplastic neuropathies, hereditary autonomic neuropathies, and infection-disease related neuropathy.

The plethora of diseases that cause these symptoms make it is very easy for physicians to make a wrong diagnosis, even though a correct diagnosis is very important for early treatment.

Chinese researchers presented a case study of a 60-year-old patient that presented numbness, orthostatic hypotension (decrease in blood pressure from a sudden movement to standing from lying or sitting), and gastrointestinal symptoms. He presented with autonomic neuropathy as the initial symptom and subsequently developed albuminocytologic dissociation (increase in protein levels) in the cerebrospinal fluid (CSF).

A series of tests, such as congo red staining, electromyogram (EMG), lumbar puncture, Bence Jones protein urine test, serum electrophoresis blood test, sural nerve and rectal membrane biopsies, transthyretin (TTR) gene sequencing, and bone marrow puncture were performed to determine a diagnosis.

Congo red staining, which shows the presence of amyloid deposition, was positive for amyloid deposits. Gene sequencing of TTR, a gene associated with a group of disorders called FAP, showed no mutations.

The CSF cell counts, after doing a lumbar puncture, were normal but there was an increase in CSF protein concentration. Blood cell counts, determined through bone marrow puncture, were abnormal, which indicates a bone marrow disorder (including amyloidosis). The EMG results demonstrated the presence of peripheral nerve damage, mostly in the sensory nerve fibers. Through analysis of these results, the neurologists were able to come to a diagnosis of primary amyloidosis.

“We have demonstrated that a diagnosis of amyloidosis should not be ignored in patients presenting with neuropathic onset symptoms, particularly autonomic neuropathy (such as orthostatic hypotension and gastrointestinal symptoms),” the researchers wrote.

“In such patients, neurologists should use caution to differentiate between chronic inflammatory demyelinating polyneuropathy, primary amyloidosis, and familial amyloid neuropathy,” they added.

Early diagnosis of amyloidosis can help treat patients effectively and increase the chance of survival, which is why it is imperative to consider amyloidosis as a potential cause for autonomic neuropathy symptoms.