Alkaptonuric ochronosis

Total knee arthroplasty and physical therapy for arthropathy in alkaptonuria: A 4-year follow-up case report

Introduction

Alkaptonuria is a rare autosomal recessive metabolic disorder which leads to accumulation of homogentisic acid in the body.

Case Presentation

We report a rare case of an alkaptonuria-related knee arthritis who underwent left total knee arthroplasty and received postoperative systematic physical therapy in a 57-year-old male patient. The patient has suffered from bilateral knee pain for over 4 years. The patient developed melanin pigmentation on the skin of the whole body, especially on the face and auricle. He self-reported that fresh urine was normal color but after standing overnight, the color deepened to black or soy color. He underwent routine urine examination for many times, but no obvious abnormality was found. The patient has suffered from low back pain for more than 20 years. He had been considered for lumbar disc herniation and ankylosing spondylitis after many in-hospital visits. After symptomatic medication, there was no obvious relief. We followed the patient for 4 years after surgery.

Result

The patient presented with pain relief and enhanced range of motion at the 4-year follow-up. The improvements of daily living and the pain relief suggest that the surgery is appropriate for this rare disease.

Conclusion

It is rare that the knee pain is diagnosed as alkaptonuria. After total knee arthroplasty and physical therapy, the patient had a good outcome. This case provides experience for the diagnosis and treatment of alkaptonuria-related knee arthritis.

OUP accepted manuscript

Ochronotic arthropathy is a chronic manifestation of disease in patients with alkaptonuria. Connective tissue and large joint spaces accumulate discolored homogentisic acid aggregates, resulting in joint degeneration of the axial and appendicular skeleton. One case of right shoulder ochronotic osteoarthritis treated with joint replacement is presented. To our knowledge, this is the first reported surgical intervention of ochronotic arthropathy using the reverse total shoulder arthroplasty technique.

Inflammatory rheumatic diseases in patients with ochronotic arthropathy

BACKGROUND

Ochronotic arthropathy (OcA) refers to excessive homogentisic acid (HGA) deposition in the musculoskeletal system. Our current understanding of OcA is limited, as there are less than a thousand alkaptonuria (AKU) cases reported in the literature. Herein, we investigated the rheumatological manifestations of OcA in a group of adult AKU patients.

METHODS

Adult AKU patients with symptoms suggestive of OcA were included. Patients underwent a detailed rheumatological assessment. Laboratory testing, including autoantibodies and radiological investigations such as conventional X-rays, and magnetic resonance imaging (MRI) were performed.

RESULTS

Eight out of 12 (66%) patients had symptoms consistent with OcA. The median age at OcA symptoms was 36 (27-48) years, and the presenting symptom was back pain in 87.5% of the patients. All patients had chronic back pain, and three (37.5%) had an inflammatory type of pain character. Radiographic sacroiliitis based on X-rays was present in 2 (25%) cases. MRI of the sacroiliac joints documented bone marrow edema in five (62.5%), and spinal MRI identified corner inflammatory lesions in three patients (37.5%). One patient (12.5%) had rheumatoid arthritis. Extra-articular involvement, including enthesitis (n = 1; 12.5%), interstitial lung disease (n = 1; 12.5%), and scleritis (n = 1; 12.5%), was also noted.

CONCLUSION

The frequent occurrence of OcA-related inflammatory manifestations in our patients contradicts the conventional concept of OcA as a non-inflammatory disorder. The activation of inflammatory pathways, possibly by the HGA products, may responsible for this condition.Significance and innovationsAbout three-fourths of adult ochronotic arthropathy (OcA) patients in our group had associated inflammatory disease.OcA associated inflammatory diseases were showing a severe phenotypeNearly half of the OcA patients required early prosthesis operations compared to their healthy counterparts.

Clinical and radiological outcomes of total joint arthroplasty in patients with ochronotic arthropathy

PURPOSE

Alkaptonuria is a rare metabolic disorder, and only a few case reports of total joint arthroplasty (TJA) for ochronotic arthropathy are described in the literature. We aim to analyse the functional and radiological outcomes of TJA in patients with ochronotic arthropathy.

METHODS

We retrospectively collected the data of twenty-seven TJA in sixteen patients with ochronotic arthropathy from April 2007 to December 2017. We assessed the functional outcome through pre- and post-operative modified Harris hip score (HHS) and knee society score (KSS). The hip radiographs were analysed for migration and radiolucent zones, and the knee radiographs were assessed using knee society roentgenographic evaluation and scoring system.

RESULTS

The mean follow-up was 39.4 months (12-132 months). Two patients died before the final follow-up. There was a statistically significant improvement in mean HHS from 17.8 preoperatively to 78 at the final follow-up (p < 0.001). Similarly, there was a significant improvement in mean KSS, following the surgery, from 27.2 preoperatively to 89.4 (p < 0.001). One patient developed deep infection, and another patient presented with aseptic loosening of the acetabular component after 7 years. In the radiological evaluation at the final follow-up, signs of lysis or loosening were not noted in any of the other patients.

CONCLUSION

End-stage arthritis in ochronotic arthropathy is not uncommon. These patients can have multiple joint involvements, and the need for multiple surgeries should be considered. TJA in ochronotic arthropathy leads to a significant improvement in the functional outcome compared with the preoperative disability.

Assessment of Thyroid Function in Patients With Alkaptonuria

IMPORTANCE

Alkaptonuria is an autosomal recessive disorder caused by pathogenic variants in the HGD gene. Deficiency of the HGD enzyme leads to tissue deposition of homogentisic acid (HGA), causing severe osteoarthropathies and cardiac valve degeneration. Although HGD is vital for the catabolism of tyrosine, which provides the basis for thyroid hormone synthesis, the prevalence of thyroid dysfunction in alkaptonuria is unknown.

OBJECTIVE

To assess thyroid structure and function in patients with alkaptonuria.

DESIGN, SETTING, AND PARTICIPANTS

A single-center cohort study was conducted in a tertiary referral center including patients with alkaptonuria followed up for a median of 93 (interquartile range, 48-150) months between February 1, 2000, and December 31, 2018. The alkaptonuria diagnosis was based on clinical presentation and elevated urine HGA levels. A total of 130 patients were considered for participation.

MAIN OUTCOMES AND MEASURES

Prevalence of thyroid dysfunction in adults with alkaptonuria compared with the general population. Thyrotropin and free thyroxine levels were measured by immunoassay and repeated in each patient a median of 3 (interquartile range, 2-22) times. Neck ultrasonographic scans were analyzed in a subset of participants. Logistic regression was used to test the association of thyroid dysfunction with age, sex, thyroid peroxidase (TPO) antibodies, serum tyrosine levels, and urine HGA levels.

RESULTS

Of the 130 patients, 5 were excluded owing to thyroidectomy as the cause of hypothyroidism. The study cohort consisted of 125 patients; the median age was 45 (interquartile range, 35-51) years. Most of the patients were men (72 [57.6%]). The prevalence of primary hyperthyroidism was 0.8% (1 of 125 patients), similar to 0.5% observed in the general population (difference, 0.003; 95% CI, -0.001 to 0.04; P = .88). The prevalence of primary hypothyroidism was 16.0% (20 of 125 patients), which is significantly higher than 3.7% reported in the general population (difference, 0.12; 95% CI, 0.10-0.24; P < .001). Women were more likely to have primary hypothyroidism than men (odds ratio, 10.99; 95% CI, 3.13-38.66; P < .001). Patients with TPO antibodies had a higher likelihood of primary hypothyroidism than those without TPO antibodies (odds ratio, 7.36; 95% CI, 1.89-28.62; P = .004). There was no significant difference in the prevalence of thyroid nodules between patients in this study (29 of 49 [59.2%]) vs the general population (68%) (difference, 0.088; 95% CI, -0.44 to 0.73; P = .20) or of cancer (7% vs 5%; difference, 0.01; 95% CI, -0.01 to 0.17; P = .86).

CONCLUSIONS AND RELEVANCE

The high prevalence of primary hypothyroidism noted in patients with alkaptonuria in this study suggests that serial screening in this population should be considered and prioritized.

ARTHROPLASTY IN ALKAPTONURIC OCHRONOSIS

Ochronotic degenerative arthropathy occurs in patients with alkaptonuria. Alkaptonuria disorder is an extremely rare disease characterized by black pigmentation of various tissues (e.g., cartilage and connective tissue). Ochronotic arthropathy is a disabling disease that primarily affects the large joints. Like other metabolic diseases that involve the musculoskeletal system, care must be taken with regard to the quality of the affected bones, tendons and ligaments, and therefore the stability and survival of joint prosthesis. The following is a report of a 66-year-old man affected by several musculoskeletal manifestations of alkaptonuria with severe joints disruption, who was successfully treated with total left hip and total right knee replacements. Surgical, anesthesiological and postoperative management of these patients may require more vigilance due to the associated comorbidities of this disorder.

Calcaneal Avulsion of an Ochronotic Achilles Tendon: A Case Report

Alkaptonuria is a hereditary disorder of phenylalanine and tyrosine, with an incidence of approximately 1/200,000 to 1/1,000,000. Ochronosis is the accumulation of homogentisic acid and its metabolites in connective tissues such as the tendons, cartilage, and skin. In the present case study, a 50-year-old male presented with a nontraumatic calcaneal avulsion without a previous diagnosis of ochronosis. To the best of our knowledge, little information has been reported of this pathology in the Achilles tendon and the surgical management.

An Osteochondral Allograft in a Patient with Ochronosis: A Case Report

CASE

When a 31-year-old man with no prior medical history underwent diagnostic arthroscopy for posttraumatic knee pain, ochronotic arthropathy was identified. Subsequent blood tests led to the diagnosis of alkaptonuria. After a discussion regarding his future military career and prognosis, he elected to proceed with osteochondral allograft transplantation surgery (OATS). He was able to return to active-duty service with minimal knee pain. At the 32-month postoperative visit, he had functional, pain-free motion and an excellent Hospital for Special Surgery (HSS) knee score.

CONCLUSION

Alkaptonuria is an uncommon metabolic disorder that causes arthropathy of peripheral joints. When there is a focal defect, an osteochondral allograft is a valid, joint-preserving option that allows return to activity.

Orthopedic Manifestations of Ochronosis: Pathophysiology, Presentation, Diagnosis, and Management

Ochronotic arthropathy occurs in patients with alkaptonuria, manifesting first in the intervertebral discs of the lumbar spine, with subsequent degeneration most often observed in the knee, hip, and shoulder joints. Efforts at treatment are targeted at minimizing the damaging effects of the underlying metabolic disorder on the articular cartilage. Vitamin E and N-acetyl cysteine are potential therapies because of their scavenging of free radicals and consequent limitation of oxidative damage to joint tissue. Arthroscopy has been found to be an effective diagnostic tool in cases of suspected ochronosis. Arthroplasty performed in patients with ochronotic arthropathy suggests that the procedure is effective in the alleviation of joint pain and the improvement of mobility. Perioperative management of these patients may require more careful consideration pertinent to the associated comorbidities of this disorder.