A case study on sequential tendon rupture in a patient

 By Dr. Namdev Gorgile,

Introduction :
Alkaptonuria is a rare inherited genetic disease caused by a lack of the enzyme Homogentisic Acid Oxidase (HGA). This enzyme catalyses the breakdown of homogentisic acid, a byproduct of the aromatic amino acids phenylalanine and tyrosine. The condition is extremely rare, affecting only 1 in 100,000 to 250,000 people. The HGA is abundantly excreted in the urine of these patients. Despite this, HGA levels in the blood and body tissues are elevated. A lack of homogentisic acid causes an accumulation in the blood and tissues, affecting the hyaline cartilages, skin, sclera, tendon, joints, and intervertebral disc. It is also linked to lower bone mineral density. The condition also has an impact on the respiratory, genitourinary, and cardiovascular systems. The polymer known as Ochronotic pigment, also known as Ochronosis, affects hyaline cartilage, particularly in weight-bearing joints such as the knee. Ochronotic arthritis usually appears in the third decade of life. Finally, joint replacement is required; on average, this occurs at the age of 55. Ochronotic arthritis is characterised by articular space narrowing, bone sclerosis, and effusion. These ruptures are more common in older age groups, typically those over the age of 40. In older patients, the rupture usually occurs at the osseo-tendinous junction, whereas in younger patients, the rupture usually occurs in the mid-tendinous area. We present a case of a Sequential tendo Achilles tendon rupture followed by a right quadriceps tendon rupture ten years later.

Discussion: Homogentisate 1,2-Dioxygenase (HGO) deficiency causes the accumulation of homogentisic acid, which is rapidly cleared in the kidney and excreted1. The production of large amounts of HGA in the urine on a daily basis causes it to become dark when standing. HGA oxidises to benzoquinones in urine, just as it does in tissues, forming melanin-like polymers. Ochronosis is caused by the accumulation of HGA and its metabolites in tissues, which results in darkening of cartilaginous tissues and bone, arthritis and joint destruction, and deterioration of cardiac valves [8]. Although nitisinone inhibits the enzyme that produces HGA, there is no effective treatment for this disorder. Antioxidants such as ascorbic acid could also be used to achieve therapy because reducing HGA oxidation could increase urinary HGA excretion. Furthermore, ascorbic acid has been shown to inhibit HGA polyphenol oxidase, resulting in a decrease in Benzoquinone Acetic Acid (BQA) synthesis, a byproduct of HGA oxidation that causes tissue injury. The only disabling effect of Alkaptonuria Arthropathy is brittleness and fragmentation of the articular cartilage, which also causes a non-specific synovitis of the affected joints. The spine and major weight-bearing joints are the most commonly affected, with symptoms typically appearing in the fourth decade. The numerous reports on Alkaptonuria are limited to degenerative manifestations in joints, but there are no reports of homogentisic acid deposition in tendons causing spontaneous rupture. Homogentisic acid is widely deposited in connective tissue, and such pigmentation must include tendons, which are primarily composed of Type I collagen. The accumulation of homogentisic acid inhibits collagen cross-linking, resulting in a reduction in collagen structural integrity. As a result, the likelihood of spontaneous rupture increases. There is no specific treatment for Alkaptonuria Arthropathy; instead, it is a combination of physiotherapy, analgesia, and rest. It has been reported that reducing tyrosine and phenylalanine in the diet reduces homogentisate excretion. It is unknown whether dietary restriction from infancy would prevent or reduce later complications, but such an approach seems reasonable. Adults and older children should consume up to 1 g of vitamin C per day. Ascorbic acid's mild antioxidant properties help to delay the conversion of homogentisate to the polymeric material that is deposited in cartilaginous tissues. Genetic advancements provide hope that corrective measures are on the way. In a murine model of Alkaptonuria, 2(2 nitro-4-trifluoromethylbenzoyl)1,3-cyclohexanedione (NTBC) was found to be a strong inhibitor of the enzyme hydroxyl phenyl pyruvate dioxygenase, which catalyses the formation of homogentisic acid. The discovery of the active compound could lead to the development of the first pharmacotherapeutic agent for this metabolic disease.
Summary: Ochronosis is a rare metabolic disorder that can cause tendon rupture, osteoarthritis, and back pain. Prophylactic therapy, which includes a protein-restricted diet and ascorbic acid, may help to reduce complications. We decided to report this case because he presented with a Sequential rupture of both the Achilles tendon and the right quadriceps tendon. The ultimate goal of treatment may be to replace the missing homogentisic acid oxidase enzyme through genetic engineering.

It is always preferable to keep these patients informed about the potential consequences of disease and the need for regular follow-up for early detection and treatment of any musculoskeletal problems.
 

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