Autosomal cystinuria

Cystinuria is an autosomal recessive disease with an incidence of 1 In 15,000 live births in the United States. 

In 54 patients, a kidney biopsy was performed 13.2 8.9 days after onset (n = 32). In all patients, the findings suggested either acute tubular necrosis or its recovery phase. The underlying diseases included kidney diseases such as IgA nephropathy [138], minimal change nephrotic syndrome [139], autosomal dominant polycystic kidney disease (ADPKD) [140], and cystinuria [67]. 

Cystinuria is an autosomal recessive condition in which there is excessive urinary excretion of cystine because of a defect in proximal renal tubular reabsorption. In the most common form of the disease there is also excess excretion of the dibasic amino acids (lysine, ornithine, and arginine). These share the same renal tubular transporter although their presence in excess in urine appears benign. More rarely, isolated cystinuria is seen. The reader should note that cystinuria should not be confused with cystinosis, which is a condition associated with intracellular accumulation of cystine but not excess urinary excretion of cystine. 

Deficiencies of methionine adenosyltransferase, cystathionine 8-synthase, and cystathionine )/-lyase have been described. The first leads to hypermethioninemia but no other clinical abnormality. The second leads to hypermethioninemia, hyperhomocysteinemia, and homo-cystinuria. The disorder is transmitted as an autosomal recessive trait. Its clinical manifestations may include skeletal abnormalities, mental retardation, ectopia lentis (lens dislocation), malar flush, and susceptibility to arterial and venous thromboembolism. Some patients show reduction in plasma methionine and homocysteine concentrations and in urinary homocysteine excretion after large doses of pyridoxine. Homocystinuria can also result from a deficiency of cobalamin (vitamin B12) or folate metabolism. The third, an autosomal recessive trait, leads to cystathioninuria and no other characteristic clinical abnormality. 

Hartnup disease Is another genetically determined and relatively rare autosomal recessive disorder. It is caused by a defect in the transport of neutral amino acids across both intestinal and renal epithelial cells. The signs and symptoms are, in part, caused by a deficiency of essential amino acids (see Clinical Comments). Cystinuria and Hartnup disease involve defects in two different transport proteins. In each case, the defect is present both in intestinal cells, causing malabsorption of the amino acids from the digestive products in the intestinal lumen and in kidney tubular cells, causing a decreased resorption of these amino acids from the glomerular filtrate. 

Cystinuria is an autosomal recessive disorder of renal mbular teab-sorption of cystine, ornithine, arginine and lysine (mnemonic COAL). Cystine (a dimer of cysteine Chapter 6) is sparingly soluble and accumulates in the tubular fluid, forming bladder and kidney stones (cystine urolithiasis). Cystine is so-called because cystine stones were discovered in the cyst (i.e. bladder). 

Cystinuria is one of the most frequent genetic disorders with an overall prevalence of 1 7,000 and an autosomal recessive inheritance. It is caused by a defective transport of cystine and the dibasic amino... 

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