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Addison Disease: Primary adrenal insufficiency (hypocortisolism and hypoaldosteronism) is often termed Addison disease. Addison disease is relatively rare, occurring most often in adults 30 to 60 years of age, although it may appear at any time. The most common cause of Addison disease in the United States is autoimmune destruction of the adrenal cortex and it is more 63
common in women. Other causes include infections (tuberculosis, fungal infections, human immunodeficiency virus [HIV]), infiltrative diseases (amyloidosis, metastatic carcinoma), or bilateral adrenal hemorrhage. Adrenoleukodystrophy and adrenomyeloneuropathy are two rare types of X-linked adrenal deficiency that lead to symptoms of hypocortisolism and progressive neurologic symptoms. Pathophysiology. Addison disease is characterized by inadequate corticosteroid and mineralocorticoid synthesis and elevated serum ACTH levels (loss of negativefeedback). Before clinical manifestations of hypocortisolism are evident, more than 90% of total adrenocortical tissue must be destroyed. Idiopathic Addison disease (organ-specific autoimmune adrenalitis) causes adrenal atrophy and hypofunction and is an organ-specific autoimmune disease. (Autoimmunity is discussed in Chapter 9.) It may occur in childhood (type 1) or adulthood (type 2). 21-Hydroxylase autoantibodies and autoreactive T cells specific to adrenal cortical cells are present in 50% to 70% of individuals with idiopathic Addison disease; this percentage increases in younger persons and in those with other autoimmune diseases. This deficiency allows the proliferation of immunocytes directed against specific antigens within the adrenocortical cells. The adrenal glands in idiopathic Addison disease are smaller than normal and may be misshapen. Several genes have been identified. Idiopathic Addison disease often is associated with other autoimmune diseases and in such cases is known as autoimmune polyendocrine syndrome (APS). APSI (APS type I) is inherited as autosomal recessive with childhood onset and includes Addison disease, hypoparathyroidism, mucocutaneous candidiasis, and other less common symptoms. APSII (APS type II) is more common and involves Addison disease, immune thyroid disease, diabetes mellitus, celiac disease, and hypogonadism. The symptoms of Addison disease are primarily a result of hypocortisolism and hypoaldosteronism and are often vague and not well-defined. With mild to moderate hypocortisolism, symptoms usually begin with weakness and easy fatigability. Skin changes, including hyperpigmentation and vitiligo, may occur. As the condition progresses, anorexia, nausea, vomiting, and diarrhea may develop. Symptoms of mineralocorticoid deficiency include hypovolemia, postural hypotension and dizziness, dehydration, hyperkalemia, and salt craving. Of greatest concern is the development of hypotension that can progress to complete vascular collapse and shock. This is known as adrenal crisis or addisonian crisis, and develops with undiagnosed disease, acute