Alkaptonuria or Black urine – A rare genetic disorder
Alkaptonuria is an autosomal recessive condition. It arises in people who have inherited two mutual genes – one from each parent. It is a rate inherited genetic metabolic disorder. Globally, the incidence of Alkaptonuria is one in 2.5 lakh. A high number of cases have been detected in the Dominican Republic and very few in India.
Those affected with Alkaptonuria are unable to process amino acids, phenylalanine and tyrosine. As a result, a toxic tyrosine byproduct called homogentistic acid or alkapton which accumulates in the blood, is excreted in urine in large amounts and this urine, on exposure to light, turns black hence it is also called as black urine disease.
Another distinctive characteristic is that ear wax exposed to air turns red or black after several hours. These patients have pigmentation in all parts of the body like the ear lobe, palms, face, gums, cornea of the eye. Since a large quantity of homogentistic acid is deposited in the connective tissues, they also turn black.
And, the most affected organs because of this rare disease are the kidneys, heart and joints. The main symptoms which appear at a relatively young age include joint pain and back pain [because of cartilage damage], decreased range of motion of joints, arthritis, coronary artery disease, valvular heart disease, stones formation in kidneys and prostate.
Other visible signs of the disease are pigmentation in nails and knuckles, darkened skin on sun exposed areas, around sweat glands, and brown coloured sweat. However, there is no treatment for Alkaptonuria.
Case study of Alkaptonuria
The patient will suffer from pain in his left leg and lower back for the past from many years, if such patients are diabetic or suffering from high blood pressure it will aggravate the condition further.
Under such conditions radiological examinations reveal that such patients had this rare genetic disorder, Alkaptonuria. It completely damages cartilages and bones of the left hip joint and it clearly shows marked narrowing of disc space and calcium deposits in the spinal column.
Routine pre-operative investigations need to be conducted along with angiogram and the test will reveal blocked heart vessels and if confirmed then artery bypass graft surgery need to be conducted.
Surgery under these conditions will pose a challenge to surgeons as cartilages in the hip joint will become black and this will pose much responsibility to surgeons as they need to differentiate between healthy and necrosed tissues at the time of surgery. A new kind of implant, oxinium hip implant, comprising of ceramic and metal alloy, will be used for better durability, patient can walk on second day if the surgery will be successful.
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