Alkaptonuria; AKU

What is Alkaptonuria; AKU?

Alkaptonuria; AKU is a rare disease. It is also known as Homogentisic Acid Oxidase Deficiency Ochronosis.

This rare condition is not as easy to diagnose as may be thought. The classical darkening of the urine on standing is often not noticed during childhood and might not occur on a normal diet. The dark pigment of the sclera and of the ears is rarely noticed before the third decade and the presenting complaint is often of arthritis in middle age. At that stage the radiologial changes are characteristic. These include narrowing and calcification of the disc spaces and, not infrequently, fusion of the vertebral bodies. 50% of patients undergo at least 1 hip replacement by the age of 55 years. Calcification of the ear cartilages is a useful sign. Complications include rupture of intervertebral discs and possibly myocardial disease. Rana et al., (2015) reported a case with severe vertebral disc herniations.
Pollak et al., (1993) mapped the gene to 3q2. This location was confirmed by Janocha et al., (1994). Fernandez-Canon et al., (1996) isolated the homogentisate 1,2 dioxygenase (HGO) gene. Beltran-Valero de Bernabe et al., (1998; 1999), Porfirio et al., (2000) and Zatkova et al., (2000) reported further mutations.

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* This information is courtesy of the L M D.

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What gene changes cause Alkaptonuria; AKU?

The syndrome is inherited in the following inheritance pattern/s:

Autosomal Recessive - Autosomal recessive inheritance means an affected individual receives one copy of a mutated gene from each of their parents, giving them two copies of a mutated gene. Parents, who carry only one copy of the gene mutation will not generally show any symptoms but have a 25% chance of passing the copies of the gene mutations onto each of their children.

In some cases, a genetic syndrome may be the result of a de-novo mutation and the first case in a family. In this case, this is a new gene mutation that occurs during the reproductive process.

OMIM Number - 203500 (please check the OMIM page for updated information)

The syndrome can be caused by mutations in the following gene/s location/s:
HGD - 3q13.33

What are the main symptoms of Alkaptonuria; AKU?

The typical symptoms of the syndrome are:
Growth abnormality, Hearing abnormality, Kyphosis, Hypertension, Abnormality of metabolism/homeostasis, Abnormality of the ear, Abnormal aortic valve morphology, Blue sclerae, Back pain, Arthropathy, Arthritis, Arthralgia, Aortic valve calcification, Aortic dilatation, Calcification of the auricular cartilage, Cartilage destruction, Abnormality of the nose, Abnormality of the urinary system, Abnormality of the nail, Abnormal tendon morphology, Aminoaciduria, Chondrocalcinosis, Intervertebral disk calcification, Mitral stenosis, Mitral valve calcification, Irregular hyperpigmentation, Joint swelling, Nephrolithiasis, Coronary artery atherosclerosis, Coronary artery calcification, Intervertebral disc degeneration, Limitation of joint mobility, Vertebral fusion, Reduced bone mineral density, Thickened Achilles tendon, Osteoarthritis, Prostatitis, Autosomal recessive inheritance, Pigmentation of the sclera

How does someone get tested for Alkaptonuria; AKU?

The initial testing for Alkaptonuria; AKU can begin with facial genetic analysis screening, through the FDNA Telehealth telegenetics platform, which can identify the key markers of the syndrome and outline the type of genetic testing needed. A consultation with a genetic counselor and then a geneticist will follow.

Based on this clinical consultation with a geneticist, the different options for genetic testing will be shared and consent will be sought for further testing.

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