Several well-known disorders affecting skeletal muscle either are not congenital or do not yet have any conspicuously useful laboratory test. Among these are disorders whose primary defect is located in the central nervous system or peripheral nervous system rather than in skeletal muscle itself. In this group are various neurologic diseases that secondarily result in […]
Chromosome analysis. There are several conditions, some relatively common and some rare, that result from either abnormal numbers of chromosomes, defects in size or configuration of certain single chromosomes, or abnormal composition of the chromosome group that determines sexual characteristics. Laboratory diagnosis, at present, takes three forms. First, chromosome charts may be prepared on any […]
Primary (metabolic) aminoacidopathies Phenylketonuria (PKU). Classic PKU is inherited as an autosomal recessive trait. It is uncommon in Asians and African Americans and is due to deficiency of a liver enzyme known as “phenylalanine hydroxylase,” which is needed to convert the amino acid phenylalanine to tyrosine. With its major utilization pathway blocked, phenylalanine accumulates in […]
The best known of this group are Hunter’s and Hurler’s syndromes. In these conditions there is inability to metabolize certain mucopolysaccharides, resulting in accumulation and storage of these substances in various body organs and tissues and excretion of some stored material in the urine. Hurler’s syndrome. Hurler’s syndrome is caused by deficiency of the enzyme […]
Lysosomal storage diseases are the result of genetic deficiency in certain enzymes found in tissue cell cytoplasmic lysosomes. These enzymes help metabolize certain glycoproteins, glycolipids, and mucopolysaccharides. The substance normally altered by the deficient enzyme accumulates in the cell lysosome area, and a storage disease results. The nonmetabolized substance either is stored in the tissue […]
Galactosemia. Galactosemia results from congenital inability to metabolize galactose to glucose. The most common source of galactose is milk, which contains lactose. Lactose is converted to glucose and galactose in the gastrointestinal (GI) tract by the enzyme lactase. There are three forms of galactosemia, each with autosomal recessive inheritance, and each caused by an enzyme […]
Various diagnostic modalities are available. Some genetic disorders involve chromosomes. Many chromosomal abnormalities are autosomal (not involving the sex chromosome); others are sex-linked (inherited through the sex chromosomes). In some cases there may be total or partial deletion of a chromosome, presence of an extra chromosome attached to a chromosome pair (trisomy), or translocation, when […]
Serum lactic dehydrogenase. Serum LDH levels are sometimes elevated in extensive carcinomatosis, often without any obvious reason. This is especially true in lymphoma, where it may be abnormal in up to 50% cases. However, LDH levels can be elevated in many conditions, which considerably lessens its usefulness in cancer diagnosis. Carcinoma antigen 19-9. CA 19-9 […]
These syndromes have been mentioned in the discussion of certain tumors that may be associated with MEN. These syndromes are familial, with types I and II being inherited as an autosomal dominant disorder. About one half of type III cases are sporadic. Some cases of incomplete or overlapping organ tumor patterns have been reported. Although […]
In general, when an effusion occurs, the problem is differentiation among neoplastic, infectious, and fluid leakage etiologies. Effusions due to neoplasms or infection are frequently termed exudates and those due to hydrostatic leakage from vessels are called transudates. Several criteria have been proposed to separate transudates and exudates and to differentiate among the three major […]
