Alkaptonuria: An Inborn Error of Amino Acid Metabolism

Abstract

Background:  Alkaptonuria (AKU) is a rare hereditary metabolic disorder that occupies a unique position in the history of medical and biochemical genetics because it was the first human metabolic disorder to be interpreted as genetically deter-mined. This condition is characterized by deficiency of HGAO, an enzyme that is mainly found in hepatocytes. The medical interest in alkaptonuria stems from its association with ochronosis, arthropathy and homogentisicaciduria.

Objectives:  The objective of the present study was to screen urine of children, who were less than two years of age for detection of inborn errors of amino acid and carbohydrate metabolism-with particular reference to: 1. Phenylketonuria (PKU), 2. Alkaptonuria (AKU), 3. Galactosemia, 4. Fructosuria  and 5. Pentosuria.

Place of study:  This study was performed in the department of chemical pathology of Postgraduate Medical Institute, Lahore, which is part of the first author’s studies of M. Phil. Degree in Chemical Pathology.

Study Design:  A cross sectional, hospital based study.

Methods:  In addition to chemical tests, one dimensional descending paper chromatography was used in this study for the detection of hereditary metabolic disorders.

Results:  Out of 2,000 children (1194 males and 806 females), only one female child having alkaptonuria was detected. The elder sister of this infant, investigated as part of the family study also revealed the presence of this condition.

Conclusion:  The present study has established the fact that hereditary metabolic disorders like AKU also exist in Pakistan and the paper chromatography of the urine furnishes a simple technique to identify HGA / urinary sugars and amino acids.

Keywords:  Hereditary metabolic disorders, Alkaptonuria, Homogentisicaciduria, Ochronosis, Arthropathy, Paper Chroma-tography, Pakistan.