Systemic amyloidosis from A (AA) to T (ATTR): a review.

Systemic amyloidosis is a rare protein misfolding and deposition disorder leading to progressive organ failure. There are over 15 types of systemic amyloidosis, each caused by a different precursor protein which promotes amyloid formation and tissue deposition. Amyloidosis can be acquired or hereditary and can affect various organs, including the heart, kidneys, liver, nerves, gastrointestinal tract, lungs, muscles, skin and soft tissues. Symptoms are usually insidious and nonspecific resulting in diagnostic delay. The field of amyloidosis has seen significant improvements over the past decade in diagnostic accuracy, prognosis prediction and management. The advent of mass spectrometry-based shotgun proteomics has revolutionized amyloid typing and has led to the discovery of new amyloid types. Accurate typing of the precursor protein is of paramount importance as the type dictates a specific management approach. In this article, we review each type of systemic amyloidosis to provide the practitioner with practical tools to improve diagnosis and management of these rare disorders.

Frequencies and geographic distributions of genetic mutations in transthyretin- and non-transthyretin-related familial amyloidosis.

Inherited forms of amyloidosis are rare; of these, transthyretin-related (ATTR) is the most common, but non-ATTR has been described as well. We studied a large case series of ATTR and a small series of non-ATTR to better determine the mutation frequencies and geographic distributions of these inherited forms of amyloidosis in the United States. We performed a retrospective cross-sectional study of 284 ATTR and non-ATTR patients seen at Mayo Clinic in Rochester, Minnesota, from 1 January 1970 through 29 January 2013. Mutations were identified by DNA sequencing, restriction fragment length polymorphism, or mass spectroscopy. The genetic testing method was unknown for several patients, but a small proportion were identified by family history or by classical clinical presentation associated with a specific mutation. The most common ATTR mutations were Thr60Ala (24%), Val30Met (15%), Val122Ile (10%), and Ser77Tyr (5%). Non-ATTR mutations included gelsolin (n = 3), apolipoprotein A-I (n = 6), apolipoprotein A-II (n = 1), fibrinogen A-α (n = 9), and lysozyme (n = 1). Although rare, ATTR and, to a lesser extent, non-ATTR are prevalent in the United States and should be considered for patients presenting in the appropriate clinical context.

Cerebral infarction in POEMS syndrome: incidence, risk factors, and imaging characteristics.

OBJECTIVES: To determine the risk factors and incidence of cerebral infarction associated with POEMS (polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, and skin changes) syndrome. METHODS: The Mayo Clinic dysproteinemia database was queried to identify patients with coded diagnosis of POEMS syndrome. Patients with cerebral infarction, occurring after the onset of POEMS-related symptoms, were selected. A retrospective observational study design was used to evaluate potential predictors of stroke in patients with POEMS syndrome. RESULTS: A total of 9 patients (10%; 95% confidence interval 5.4-17.9) with cerebral infarction were identified (2 women, 22%). Traditional stroke risk factors were not significantly different between the stroke and nonstroke subgroups, but hematologic abnormalities such as elevated platelet count and bone marrow plasmacytosis differed between the 2 groups. Cerebral infarction occurrence after successful treatment of the underlying condition was not observed. CT and MRI data demonstrated a wide spectrum of infarct topography in these patients. Common stroke etiologies comprised suspected vascular structural abnormalities leading to vessel dissection and stenosis, in addition to embolism from a proximal source. CONCLUSIONS: The 5-year risk of cerebral infarction in patients with POEMS syndrome is 13.4%. Evidence of plasma cell proliferation within the bone marrow and elevated serum platelet count led to increased risk of cerebral infarction in this population. We conclude that known modifiable stroke risk factors should be aggressively managed. Treatment of thrombocytosis should be considered in patients without a contraindication. Treatment of the syndrome may be the best approach to decreasing risk of cerebral infarction in these patients.

Evidence for the distortion product frequency place as a source of distortion product otoacoustic emission (DPOAE) fine structure in humans. I. Fine structure and higher-order DPOAE as a function of the frequency ratio f2/f1.

Critical experiments were performed in order to validate the two-source hypothesis of distortion product otoacoustic emissions (DPOAE) generation. Measurements of the spectral fine structure of DPOAE in response to stimulation with two sinusoids have been performed with normal-hearing subjects. The dependence of fine-structure patterns on the frequency ratio f2/f1 was investigated by changing f1 or f2 only (fixed f2 or fixed f1 paradigm, respectively), and by changing both primaries at a fixed ratio and looking at different order DPOAE. When f2/f1 is varied in the fixed ratio paradigm, the patterns of 2 f1-f2 fine structure vary considerably more if plotted as a function of f2 than as a function of fDP. Different order distortion products located at the same characteristic place on the basilar membrane (BM) show similar patterns for both, the fixed-f2 and fDP paradigms. Fluctuations in DPOAE level up to 20 dB can be observed. In contrast, the results from a fixed-fDP paradigm do not show any fine structure but only an overall dependence of DP level on the frequency ratio, with a maximum for 2f1-f2 at f2/f1 close to 1.2. Similar stimulus configurations used in the experiments have also been used for computer simulations of DPOAE in a nonlinear and active model of the cochlea. Experimental results and model simulations give strong evidence for a two-source model of DPOAE generation: The first source is the initial nonlinear interaction of the primaries close to the f2 place. The second source is caused by coherent reflection from a re-emission site at the characteristic place of the distortion product frequency. The spectral fine structure of DPOAE observed in the ear canal reflects the interaction of both these sources.

Evidence for the distortion product frequency place as a source of distortion product otoacoustic emission (DPOAE) fine structure in humans. II. Fine structure for different shapes of cochlear hearing loss.

Distortion product otoacoustic emissions (DPOAE) were recorded from eight human subjects with mild to moderate cochlear hearing loss, using a frequency spacing of 48 primary pairs per octave and at a level L1 = L2 = 60 dBSPL and with a fixed ratio f2/f1. Subjects with different shapes of hearing thresholds were selected. They included subjects with near-normal hearing within only a limited frequency range, subjects with a notch in the audiogram, and subjects with a mild to moderate high-frequency loss. If the primaries were located in a region of normal or near-normal hearing, but DP frequencies were located in a region of raised thresholds, the distortion product 2 f1-f2 was still observable, but the DP fine structure disappeared. If the DP frequencies fell into a region of normal thresholds, fine structure was preserved as long as DPOAE were generated, even in cases of mild hearing loss in the region of the primaries. These experimental results give further strong evidence that, in addition to the initial source in the primary region, there is a second source at the characteristic place of fDP. Simulations in a nonlinear and active computer model for DPOAE generation indicate different generation mechanisms for the two components. The disappearance of DPOAE fine structure might serve as a more sensitive indicator of hearing impairment than the consideration of DP level alone.