Study Design. Two cases of lumbar disc herniation with alkaptonuria are presented.
Objectives. To present a probable clinical course of lumbar disc herniation with alkaptonuria, a rare metabolic disease.
Summary of Background Data. Although lumbar disc disease is a common clinical occurrence in alkaptonuria, lumbar disc surgery is needed rarely in this disease. A patient with alkaptonuria without ochronotic signs is also rarely seen.
Methods. The cause, clinical presentation, diagnostic techniques and treatment of alkaptonuria with lumbar disc disease are reviewed.
Results. The symptoms of the patients disappeared after surgery, and there were no symptoms on follow-up.
Conclusion. Alkaptonuria frequently occurs in association with lumbar disc disease. In patients with no other signs of alkaptonuria or ochronosis, early detection of the disease is important to treat involvement of other systems (e.g., cardiovascular and urinary).
Two cases of lumbar disc herniation with alkaptonuria are presented. Alkaptonuria is frequently associated with lumbar disc disease. In patients with no other signs of alkaptonuria or ochronosis, early detection of the disease is important to treat involvement of other systems early in its course.
Alkaptonuria is a hereditary disease related to the aromatic amino acids, phenylalanine and tyrosine, and is generally transmitted in an autosomal recessive pattern. 4-6 The disease is characterized by the absence of homogentisic acid oxidase, an enzyme in the metabolic pathway of aromatic amino acids, in the liver and kidneys and the subsequent excretion of homogentisic acid in urine 3,5 (Figure 1). A black pigment produced by oxidation and polimerization of homogentisic acid deposits in all connective tissues. 3,5 This pigment has a high affinity with fibrillary collagens surrounded by abundant mucopolysaccharide substances, such as that of the hyaline cartilage of the major peripheral joints and the intervertebral discs. 3 The pigment also deposits in all the connective tissues of the body and causes a widespread discoloration depending on the amount of pigment. Discoloration of the connective tissues, called ochronosis, may vary from yellowish-brown to black. 3-5
In the patients with alkaptonuria and ochronosis, an arthropathy-causing degeneration of major joints and intervertebral discs develops. 6 The disease usually progresses from simple alkaptonuria to alkaptonuric ochronosis and finally to alkaptonuric arthropathy. 3,6 Simple alkaptonuria frequently is signaled by a black stain on the diapers in infancy and by discoloration of the urine in childhood. Thereafter, discoloration may develop in all connective tissues. Ocular pigmentation is especially prominent and appears in approximately 70% of the patients. 6
It is not possible to say whether the degenerative changes of connective tissues are related to the degree of pigmentation. 5,6 The degenerative changes of joints usually occur in persons aged more than 30 years and progress with advanced age. 3 It has been reported that arthropathy develops in approximately 30% of cases of alkaptonuria. 1 Disease is usually diagnosed in these patients before the third stage. The number of incidences of lumbar disc disease without other symptoms and signs of alkaptonuria and ochronosis is low. 5 Although intervertebral disc degeneration is frequently seen in alkaptonuria and ochronosis, 5 only a few patients treated surgically for lumbar disc disease have been reported. In these patients, symptoms and clinical signs of disc disease usually are not as prominent as might be expected from the extent of disease observed on radiographs. 3,4
In this report, two patients who had no other symptoms and signs of alkaptonuria are described. These patients were examined and a diagnosis of alkaptonuria made after blackened nucleus pulposus was seen during lumbar disc surgery.