[The hyperaminoacidurias with special reference to cystinuria]

Area of Science:

• Nephrology
• Biochemistry
• Medical Genetics

Context:

• Elevated urinary free amino acids necessitate identifying the root cause.
• Understanding tubular transport mechanisms and the role of transport proteins is crucial.

Purpose:

• To classify hyperaminoacidurias based on physiological and metabolic factors.
• To differentiate between prerenal and renal causes of increased amino acid excretion.
• To review the clinical significance and treatment of specific hyperaminoacidurias, particularly cystinuria.

Summary:

• Hyperaminoacidurias are categorized into prerenal (overflow, competitive, non-threshold) and renal (specific or generalized) types.
• Prerenal hyperaminoaciduria reflects metabolic errors, while renal types indicate tubular dysfunction.
• Generalized hyperaminoaciduria signifies severe tubular disturbance from various conditions.
• Classical cystinuria is highlighted for its clinical relevance, with treatment experience using mercaptopropionyl-glycine presented.

Impact:

• Provides a framework for diagnosing the causes of increased urinary amino acid excretion.
• Clarifies the distinction between metabolic and tubular defects leading to hyperaminoaciduria.
• Offers insights into the management of cystinuria, a clinically significant condition.