Three-generational alkaptonuria in a non-consanguineous family

OBJECTIVE

Alkaptonuria (AKU) is a rare inborn error of metabolism of aromatic amino acids and considered to be an autosomal recessive trait caused by mutations in the homogentisate 1,2-dioxygenase (HGD) gene. A dominant pattern of inheritance has been reported but was attributed to extended consanguinity in many cases. However, we have observed a non-consanguineous family segregating AKU in a dominant manner over three generations.

RESULTS

All affected individuals presented with typical features of AKU including darkening of the urine, ochronosis, arthropathy, and elevated urinary excretion of homogentisic acid. Sequence analysis of the HGD gene from genomic DNA of two affected individuals, uncle and niece, revealed a heterozygous missense mutation (M368V) in the uncle that was not present in his niece. Microsatellite genotyping demonstrated that both were heterozygous at the HGD locus and shared one haplotype. This haplotype did not contain a detectable HGD mutation. The haplotype was also found in a healthy son of the niece, making a dominant HGD mutation unlikely. Moreover, sequencing of cDNA from lymphoblastoid cells of the niece did not reveal an HGD mRNA with a potentially dominant-negative effect.

CONCLUSION

Rare causes of the uncommon AKU inheritance in this family have to be considered, ranging from the coincidence of undetectable HGD mutations to a dominant mutation of a second, hitherto unknown AKU gene.

Ochronotic arthropathy: disappearance of alkaptonuria after liver transplantation for hepatitis B-related cirrhosis

The deficiency of homogentisic acid oxidase, an enzyme that is mainly found in hepatocytes, is associated with alkaptonuria and ochronosis. We report a patient with clinical and radiologic findings of ochronotic arthropathy in whom alkaptonuria disappeared and the progressive course of the disease stopped after liver transplantation for hepatitis B-related cirrhosis.

Ochronotic arthritis: case reports and review of the literature

Alkoptunuria is an inherited autosomal recessive metabolic disorder which is caused by the lack of homogentisic acid-oxidase enzyme. It is associated with various systemic abnormalities and related to the deposition of homogentisic acid pigment in connective tissues. These pigmentary changes are termed "ochronosis". We describe two patients with ochronotic arthritis who presented with advanced degenerative changes in the lumbo-sacral spine, knee and hip. The literature, differential diagnosis and management of this rare condition are reviewed in this article.

Alkaptonuric ochronosis with aortic valve and joint replacements and femoral fracture: a case report and literature review

Alkaptonuria is a rare autosomal recessive disorder of metabolism caused by deficiency of homogentisic acid oxidase and resulting in accumulation of homogentisic acid in collagenous structures. It is characterized by homogentisic aciduria, bluish-black discoloration of connective tissues (ochronosis) and arthropathy of large joints. Less common manifestations include cardiovascular abnormalities, renal, urethral and prostate calculi. Bone fractures are unusual in ochronosis. In this report, we describe a woman, 69 years of age, with a history of dark urine since childhood and progressive pigmentation of the skin, sclera, and auricular cartilages. She had severe arthropathy requiring total joint replacement in both of her knees and right hip. She also had severe aortic stenosis requiring valve replacement, and asymptomatic nephrolithiasis. She presented with a low trauma fracture of the distal femur despite two years of alendroate therapy. We review the etiology, pathogenesis, clinical presentation, diagnosis and treatment of alkaptonuric ochronosis. Early detection is important for prevention and treatment of multiple systems. Nitisinone, a potent inhibitor of 4-hydroxyphenylpyruvate dioxygenase, dramatically reduces production and urinary excretion of homogentisic acid; however, the long-term efficacy and side effects of such therapy are unknown. Identifying the gene for alkaptonuria offers the potential for a new therapeutic approach (replacement therapy with a recombinant enzyme) in the treatment of alkaptonuric ochronosis.

[Ochronosis: a case report with multisystemic affectation, including pericardium]

Alkaptonuric ochronosis is rare disorder of tyrosin catabolism with an autosomal recessive trait. Alkaptonuric patients are deficient for homogentisate 1,2-dioxygenase. This enzymatic deficiency leads to the elimination of large amounts of homogentistic acid in the urine (Alkaptonuria) with accumulation of homogentistic acid oxidized pigment in the connective tissue (Ochronosis). The most common clinical features are dark brown discoloration of urine on exposure to air; ocular and cutaneous pigmentation; calcification of the intervertebral disc and cardiovascular ochronosis, especially calcification and stenosis of the aortic valve. The diagnosis is confirmed by detection of homogentistic acid in urine. We report a case of a 87 year old female which has all these clinical features mentioned above and pericardiac calcification, which had not been previously reported, to our knowledge.

Bilateral hip arthroplasty for ochronotic arthropathy

Ochronosis is a musculoskeletal manifestation of alkaptonuria, a rare hereditary metabolic disorder characterised by the absence of the enzyme homogentisic acid oxidase and associated with various systemic abnormalities related to the deposition of homogentisic acid pigment (ochronotic pigment). In this report, we describe a 53-year-old, HLA-B27(+) woman with ochronotic arthropathy. In addition to the typical clinical features of the disorder, she had bilateral hip involvement, which was improved by cementless total hip prosthesis.

Hereditary ochronosis: hyperpigmented skin overlying cartilaginous structures

Hereditary ochronosis, or alkaptonuria, results from deficiency of homogentisic acid oxidase. It is an autosomal recessive condition found in geographically isolated populations. The excess homogentisic acid deposits in collagenous structures, leading to unusual pigmentation of the skin overlying cartilaginous structures, but on occasion pigment is also seen in the sclera, in sweat after oxidation, and classically, in urine when left standing at room temperature. This case report highlights the pathogenesis and expression of this rare disorder.

Ochronotic arthropathy: case report and review of the literature

Alkoptonuria is an inherited metabolic disorder which is associated with various systemic abnormalities and related to the deposition of homogentisic acid pigment in connective tissues. These pigmentary changes are termed "ochronosis". We describe two patients with ochronotic arthropathy who presented with progressive and advanced degenerative changes in the lumbo-sacral spine. The literature, differential diagnosis and management of this rare condition are reviewed in this article. Management is usually conservative, but replacement surgery may be offered for severely affected major joints.

The clinical manifestations of ochronosis: a review

Ochronosis is a rare disease caused by an inherited lack of homogentisic acid oxidase. Alkaptonuria is the presence of homogentisic acid in urine. Ochronosis is characterized by the deposition of a dark pigment in tissues rich in collagen. A wide spectrum of clinical manifestations is described. The most important signs are ochronotic arthropathy, ocular and cutaneous pigmentation, genitourinary tract obstruction by ochronotic calculi and cardiovascular ochronosis, especially calcification and stenosis of the aortic valve. The constellation of these clinical signs should suggest the diagnosis which is confirmed by the detection of homogentisic acid in urine. There is no cure for the disease and treatment is based on symptomatic measures.

Rapidly progressive hip osteoarthrosis--an unusual presentation of ochronosis

A case of rapidly evolving osteoarthrosis of the right hip in a 65 year-old woman, as the presenting feature of ochronosis is described and literature reviewed. This unusual presentation may have been precipitated by an acute mechanical overload.

Alkaptonuria and ochronosis in three siblings. Ascorbic acid treatment monitored by urinary HGA excretion

Patients with alkaptonuria lack homogentisate 1,2-dioxygenase leading to retention of homogentistic acid (HGA) in body fluids and eventually to tissue deposition of oxidation products, giving rise to the clinical picture of ochronosis. Ascorbic acid is a known inhibitor of the enzyme which catalyses the oxidation of homogentisic acid (HGA) to the polymer with affinity for collagen and was used in the treatment of three siblings with alkaptonuria. Ascorbic acid 500 mg bid was administered for 12 months. Two of the siblings tolerated the treatment, and in one the symptoms improved, whereas in the other they worsened. Plasma and urinary levels of HGA were monitored with a new HPLC method. Ascorbic acid is not effective in the treatment of symptomatic ochronosis.