Clinical Pearls & Morning Reports
Primary amyloidosis can affect any organ, including the arteries, except for the brain. Read the NEJM Case Records of the Massachusetts General Hospital here.
Q: Name two diseases that may be associated with temporal arteritis and thus mimic giant-cell arteritis.
A: Vasculitis such as aortitis and periaortitis, sometimes concurrent with retroperitoneal fibrosis, is a potential manifestation of IgG4-related disease, and temporal arteritis has been reported occasionally. In rare cases, sarcoidosis can be complicated by systemic vasculitis affecting small, medium, or large vessels. In fact, sarcoidosis-associated vasculitis involving the extracranial arteries (e.g., temporal arteries) with resultant headache and jaw claudication has been reported.
Q: What causes primary amyloidosis?
A: Primary amyloidosis is a plasma-cell dyscrasia caused by deposition of protein fragments derived from abnormal immunoglobulin light chains. The mean age at diagnosis is 63 years, and men are affected more often than women. In most patients with primary amyloidosis, the amyloidogenic light chains are produced by low-level expansion of an indolent B-cell clone that arises in the context of monoclonal gammopathy of undetermined significance. In some patients, the disease occurs in association with multiple myeloma, lymphoplasmacytic lymphoma (formerly called Waldenström’s macroglobulinemia), or non-Hodgkin’s lymphoma.
A: The most frequently affected organs are the kidneys (leading to nephrotic proteinuria) and the heart (causing pump failure). Patients may also have peripheral and autonomic neuropathy, joint and soft-tissue infiltration (e.g., extraocular muscle enlargement), deposits in the lacrimal gland and salivary gland, gastrointestinal dysmotility, skin lesions (e.g., papules and ecchymosis), lymphadenopathy, splenomegaly, liver disease, respiratory manifestations (e.g., lung nodules), and bleeding diathesis. Liver involvement, which occurs in approximately 20 to 30% of cases of primary amyloidosis, may manifest as elevated aminotransferase levels, cholestasis, and hepatomegaly. Computed tomography of the liver may show areas of parenchymal hypoattenuation in patients with clinically significant amyloid deposition. Furthermore, amyloid fibrils have an affinity for calcium, and imaging studies can show calcified deposits in different organs, including the liver and lymph nodes.
A: The diagnosis of amyloidosis requires the identification of amyloid fibrils in tissue. On microscopic examination, these fibrils show a pathognomonic apple-green birefringence under polarized light after Congo red staining. If amyloid material is identified, the next steps are to determine the type of amyloid with the use of immunohistochemical studies or laser capture microdissection followed by mass spectrometry, as well as to assess the extent and severity of the disease. Where available, imaging with radioiodinated serum amyloid P component can be used to measure the burden of disease and monitor the response to treatment.