Doctors Report Case of Late-Onset FAP With Difficult Diagnosis

Joana Fernandes, PhD avatar

by Joana Fernandes, PhD |

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Doctors reported the case of a man with late-onset familial amyloidotic polyneuropathy (FAP) with heart complications. The team’s analysis of the case prompted its members to call for early diagnosis of patients to prevent mortality due to FAP.

The study, titled “Late-onset Familial Amyloidotic Polyneuropathy with Bence Jones Proteinuria and Cardiomyopathy,” was published in the Journal of Neurosciences in Rural Practice.

FAPs are a group of life-threatening multi-system disorders resulting from genetic mutations in the transthyretin gene (TTR).

The 70-year-old man had a history of Type 2 diabetes and alcoholism. He also had been diagnosed with erectile dysfunction and, for the past year, had a history of tingling and numbness in his hands and feet. Six months before, he also experienced increasing loss of strength in all four limbs and difficulty walking.

Doctors identified cutaneous ulcers on both feet and a neurological examination revealed neuronal damage (polyneuropathy) and loss of muscle mass, especially in the quadriceps, calf, forearm muscles and in both hands. He later developed heart complications and diarrhea.

Doctors performed several other exams, including biopsies of abdominal fat and bone marrow, but could not find the reason for the patient’s condition. He later developed neurological complications, which resulted in his death two years after the first medical appointment.

A genetic analysis identified a mutation in the TTR gene, which helped diagnose the patient with FAP. Also, three out of nine of his relatives were found to be carriers of the same genetic defect.

“Diagnosis in the later stages of the disease, as in our case, is more common in patients who have no known family history, …, and more severe cardiac impairment,” doctors wrote. “We should point out that these late-onset cases are even more difficult to diagnose because a biopsy is less likely to reveal typical amyloid deposits. Our patient also presented other factors adding to the initial diagnostic confusion, including two other potential causes of polyneuropathy: diabetes mellitus and alcohol dependency.”

“Considering that this disease will have a major impact on the lives of the patient and family members, an early diagnosis is crucial for making important treatment decisions,” they added. “It introduces the possibility of using disease-modifying treatment or integral multidisciplinary treatment, and of avoiding inappropriate and aggressive therapies (such as chemotherapy for … amyloidosis). It may also enable detection of carriers or cases in early stages.”