HIVImmunosuppression Related Nervous System Diseases

This group of diseases comprises numerous opportunistic infections and the primary CNS lymphoma.

Opportunistic Infections

A great number of pathogens, dormant in the neural tissue, become reactivated by the immunosuppressed

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FIGURE 6.13

HIV-encephalitis. Microglial nodules with multinucleated giant cells (A) in the white matter (HE) and (B) brainstem (Holmes— H-E). C. Expression of HIV p24 antigen in cells of microglial nodule (immunostain).

FIGURE 6.13

HIV-encephalitis. Microglial nodules with multinucleated giant cells (A) in the white matter (HE) and (B) brainstem (Holmes— H-E). C. Expression of HIV p24 antigen in cells of microglial nodule (immunostain).

FIGURE 6.14

HIV leukoencephalopathy. A. Macrosection from the cerebral hemisphere shows multiple focal losses of myelin (LFB-CV-stain). B. Microscopic picture shows focal disintegration of myelin and axons (Holmes stain).

FIGURE 6.14

HIV leukoencephalopathy. A. Macrosection from the cerebral hemisphere shows multiple focal losses of myelin (LFB-CV-stain). B. Microscopic picture shows focal disintegration of myelin and axons (Holmes stain).

FIGURE 6.15

HIV myelopathy. Drawing of distribution of lesions in posterior and lateral columns.

FIGURE 6.15

HIV myelopathy. Drawing of distribution of lesions in posterior and lateral columns.

TABLE 6.4.

Major Opportunistic Pathog

ens in AIDS

Viruses

Fungi

Cytomegalovirus

Cryptococcus neoformans

JC, SV40 viruses

Candida

Varicella-zoster

Aspergillus fumigatus

Herpes simplex 1 and 2

Histoplasma capsulatum

Epstein-Barr virus

Coccidioides immitis

Human herpes virus 6

Protozoa

Bacteria

Toxoplasma gondii

Mycobacterium

Acanthamoeba

tuberculosis

Strongyloides stercoralis

Streptococcus

Spirochaeta

pneumoniae

Treponema pallidum

FIGURE 6.16

HIV polyneuropathy. A 40-year-old man presented with progressive flaccid paraparesis and loss of deep tendon reflexes. After a 6-month clinical course, he died. Peripheral nerve from the lumbosacral plexus shows (A) focal lymphocytic infiltrations and fibrosis (HE) and (B) myelin degeneration (LFB-CV).

state of the host and produce a broad spectrum of diseases (Table 6.4). Toxoplasmosis, CMV infection, and cerebral mycoses are the most common. Since the introduction of HAART, the incidence of these treatable infections has apparently declined. But, the incidence of Mycobacterium tuberculosis infection is rising. Treponema pallidum, in addition to causing meningitis and meningovascular syphilis, may evoke a severe necrotizing encephalitis (quaternary neurosyphilis).

Pathology. The pathologic features of opportunistic infections are generally similar to those that would occur in immunocompetent patients, but the inflammatory reaction may be less, the necrotic process more destructive, and the clinical course more malignant.

FIGURE 6.17

HIV-associated primary B-cell cerebral lymphoma in a 42-year-old man who died of Pneumocystis carnii pneumonia. A. Coronal section shows a poorly demarcated, grayish tan mass lesion with irregular margins in the basal ganglia. B. It consists of small- and medium-sized lymphocytes arranged around blood vessels (HE) and (B) surrounded by a rich reticulin network (Gömöri stain).

FIGURE 6.17

HIV-associated primary B-cell cerebral lymphoma in a 42-year-old man who died of Pneumocystis carnii pneumonia. A. Coronal section shows a poorly demarcated, grayish tan mass lesion with irregular margins in the basal ganglia. B. It consists of small- and medium-sized lymphocytes arranged around blood vessels (HE) and (B) surrounded by a rich reticulin network (Gömöri stain).

These patterns may change, however, in patients who have received HAART. The pathologic process may "burn-out"—lacking inflammation and detectable pathogens—probably due to patients' longer survival.

Primary Cerebral Lymphomas

These lymphomas occur in about 20% of AIDS patients. They are often multicentric and situated in the deep gray structures, corpus callosum, brainstem, and cerebellum. Grossly, they are poorly demarcated from the surrounding parenchyma, firm or friable, grayish or tan, and often necrotic. Histologically, they are pleomorphic, composed of small noncleaved cells and large immuno-blastic cells of B-cell origin (Fig. 6.17). Some malignant B-cell lymphomas are causally associated with the Epstein-Barr virus.

Clinically, lymphomas present with focal neurologic symptoms and signs and altered mentation. On CT scan, they may appear as hypo-, iso-, or hyperdense lesions. With contrast material, they display ring or homogenous enhancement on CT and Tl-weighted MRI.

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