Forensic Pathology for Police - Brainshare Public Online Library

Infectious Disease 207
to as “hypoxia.” An extreme form of hypoxia is referred to as “anoxia,” where
essentially no oxygen is delivered to the tissue. Hypoxia/anoxia can be transient
or sometimes relatively permanent. Depending on the tissue affected, the extent
of hypoxia, and the duration of the hypoxia, the tissue may actually die while the
remainder of the body’s organs/tissues/cells continue to live and function normally.
When cells/tissues die in this manner, they are said to have experienced “necrosis,”
and the dead area is said to be “necrotic.” The name applied to an area of necrotic
tissue caused by hypoxia is “infarct.” Therefore, an “infarction” is a localized area
of necrotic (dead) tissue/organ within a living person. It takes many hours for necrosis
to be visible grossly as well as microscopically, following the actual physiologic
event. As such, if someone dies immediately or shortly after experiencing an infarct,
the infarct will not be evident.
One method of categorizing diseases is to describe diseases based on the organ
system involved, such as the cardiovascular system or the respiratory system. This
is especially useful for diseases that primarily affect one system. Some disorders,
however, affect multiple systems. Another categorization scheme involves basic
physiologic mechanisms of disease. For example, some diseases primarily involve
blood vessel function; some involve infection; some are primarily immune disorders;
some are congenital anomalies (birth defects); some are molecular, related
to genetic mutations; some involve increased workload or other stressors; some
are primarily electrical in nature, such as cardiac conduction system abnormalities
and brain seizures; and some are primarily metabolic in nature. The electrical and
metabolic disorders can be particularly difficult or impossible to identify at autopsy.
In the remainder of this chapter, an attempt will be made to present natural diseases
that can lead to death, based on the physiologic mechanism or the organ system
involved, followed by several miscellaneous categories that do not fit nicely into a
specific organ system. Several disorders that may affect children are presented in this
chapter, but some are described in further detail elsewhere. The reader is referred to
Chapter 20 (Deaths in Infancy and Childhood) for additional descriptions of natural
death in children.
Infectious Disease
As with many of the other topics discussed in this chapter, it is far beyond the
scope of this text to provide sufficient details regarding every possible infectious disease
which exists. In general terms, infections involve tissue damage and pathologic
effects as a result of the growth of a micro-organism on or within the body. As such,
when micro-organisms reside on or within the body without causing pathologic
changes, it is not considered an infection. These organisms are called “commensal
organisms” or “normal flora.” Occasionally, one of these can overgrow and cause
an infection, but certain special circumstances are typically required.
There are several different categories of infectious organisms, including bacteria,
mycobacteria, fungi, viruses, parasites, and prions (see Central Nervous System
section). Oftentimes, bacteria produce an inflammatory process characterized by