Chapter 57

After studying this chapter, you should be able to:

• Appreciate the importance of a sound knowledge of Biochemistry and Genetics in understanding and managing many clinical conditions.
• Understand the general features and some aspects of management of the following conditions: adenosine deaminase deficiency; Alzheimer disease; cholera; colorectal cancer; cystic fibrosis; diabetic ketoacidosis; Duchenne muscular dystrophy; acute ethanol intoxication; acute gout; hereditary hemochromatosis; primary hypothyroidism; kwashiorkor and protein-energy malnutrition; myocardial infarction; obesity; primary osteoporosis; xeroderma pigmentosum.

In this final chapter, 16 case histories are presented and discussed. They illustrate the importance of knowledge of Biochemistry for the understanding of disease. Of course, as has been shown throughout the text, Biochemistry is also crucial for the understanding of health and wellness.

Most of the diseases discussed here are prevalent, or relatively prevalent, in a global sense. (Prevalence is the proportion of persons in a given population that has a particular disease at a point or interval of time.) However, two (xeroderma pigmentosum and severe combined immunodeficiency disease due to deficiency of adenosine deaminase [ADA]) are relatively rare. They are included because they illustrate two crucial biologic facts: the importance of DNA repair and of the immune system as protective mechanisms. In addition, ADA deficiency is the first disease for which gene therapy was performed in humans.

The reference values for laboratory tests cited in the cases below may differ from these listed by laboratories with which the reader may be familiar. This is because reference values from different laboratories vary somewhat, in part due to different methodologies. In this chapter, laboratory results are generally given as SI units (Systeme International d'Unites). Chapter 56 presents some of the basic principles concerned with the ordering and interpretation of laboratory tests. Table 56–11 lists the majority of the normal values for the lab tests referred to in this chapter, and gives both SI and “conventional” values (as widely used in the United States).

The doses of drugs administered in the treatment of the cases described here are not generally given; the reader should check these out on her/his own.

Causation

Genetic (due to mutations in the gene encoding ADA). Deficiency of ADA affects the immune system.

History and Physical Examination

A young girl aged 11 months was brought by her parents to a children's hospital. She had had a number of attacks of pneumonia and thrush (oral infection usually due to Candidaalbicans) since birth. The major findings of a thorough workup were very low levels of circulating lymphocytes (ie, severe lymphopenia) and low levels of circulating immunoglobulins. The attending pediatrician suspected SCID.

Laboratory Findings

Analysis of a sample of red blood cells revealed a very low activity of ADA and also a very high level (about 50 times normal) of dATP. This ...

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