The term “ochronosis” originates from a Greek word “ochre,” which refers to yellow discoloration ^[1]. Ochronosis is a rare autosomal recessive disorder occurs due to mutation of HGO gene. It is characteristized by deficiency of enzyme homogentisic acid oxidase which leads to accumulation of homogentisic acid ^[2]. Patients usually do not develop any symptoms in childhood but later in life homogentisic acid got accumulated and polymerized to form blue-brown pigment which gets deposited in connective tissue, ultimately resulting in brittle and weak tissue ^[3]. The patient can present with dark pigmentation of sclera, ear cartilage, nasal cartilage and interdigital area in hands, and urine turns dark on exposure to air ^[3]. This deposition of homogentisic acid with time can weaken the connective tissue in spine and peripheral joints which lead to ochronotic spondylosis and arthropathy ^[4]. Physical finding may include joint line tenderness, crepitus, decreased, and painful range of motion. Although it is rare cause of early arthritis, still it should be ruled out if the patient only come with pain and swelling around joint as patients with seronegative arthritis may have similar presentation. It also requires high index of clinical suspicion as test for homogentisic acid is not readily available. However, ochronosis usually does not involve small joint of hands, it apparently damages large joint of hip, knee, and spine so it can be easily differentiated ^[5]. There are some reports which showed decreased bone mineral density in cases of ochronosis due to increased bone resorption as homogentisic acid got deposited in bone matrix and damaged the bone cells ^[6]. This bone loss could possibly be the reason for common finding of fracture neck of femur and scoliosis in cases of ochronosis. Apart from joint cartilage and bone, it may also involve tendons, muscles, muscles sheaths, fascias, joint capsule and heart valve. Hence, dissection and exposure during surgery can be really challenging. Moreover, anesthetist should be aware of any cardiorespiratory involvement before surgery ^[7]. We report a case of 56-year-old female with history of fall and chronic back, knee pain which then diagnosed as ochronotic arthropathy.

A 56-year-old female presented to emergency department with history of fall at home 2 weeks back. The patient was managed at home for 2 weeks and brought to hospital when patients’ condition started deteriorating and she developed bed sores. On physical examination, right lower limb was shortened, externally rotated and the patient was not able to do hip flexion. Joint line tenderness and swelling was present on right hip. The patient also complained of chronic back ache and bilateral knee pain from past 10 to 15 years due to which she had difficulty walking without support. On plain radiograph of pelvis, we found fracture neck of femur right side (Fig. 1). Spine and knee radiograph showed fused vertebrae with scoliosis left side and grade 4 osteoarthritis bilateral knee, respectively (Fig. 2 and 3). Skin traction applied on left leg and patient planned for surgery. As the patient was neglected for 2 weeks after history of injury, had bed sores and patient belongs to low socioeconomic status, so the patient was planned for bipolar hemi-arthroplasty instead of total hip replacement. The patient was prepared for surgery hip joint opened with posterior-lateral incision. Subcutaneous tissue and abductor muscle with tensor fascia latae dissected. Some black nodules were observed in subcutaneous tissue while dissection. Femur rotated internally to exposed external rotator muscle. There was stiffness which was felt while internal rotation of femur and there was popping sound during exposure. Even after dissection of external rotators exposure of joint and retraction of tissue was difficult. Incision was increased and more soft-tissue dissected to visualize joint capsule. The capsule of joint was also contracted and after taking incision on capsule, cavity was dry and there was no joint fluid. Removal of femur head from acetabulum was more difficult than usual. There was brown-black pigmentation seen on head of femur and acetabulum (Fig. 4). Femur head removed, measured, and femur canal prepared for cementing. Rotation of femur was also restriction due to tightening of muscles and tendons. Ultimately, femur canal prepared and bipolar implant were inserted with bone cement. After that, wound washed and closed in multiple layers. No other complication was observed during surgery. After finding black head of femur, sample was sent for histopathology and for staining to rule out fungal infection. Again history was taken and thorough examination was done post-operatively, there were brown-black spots in sclera and dark pigmentation was observed on hands and ears (Fig. 5). The patient was advised in-bed mobilization next day after surgery and full weight walking was tried on 2^nd day after surgery. She faced difficulty in doing normal post-operation physiotherapy regimen and was unable to walk. Hence, she was kept on in-bed mobilization exercises till 2 months.

Ochronosis is a very rare genetic disorder found in few people in millions. The patient usually present in forth decade of life with blackening of urine, dark pigmentation of tissue in sclera, ear, nose, and skin due to accumulation of homogentisic acid ^[8]. It can be diagnosed by determination of homogentisic acid in urine. No definitive treatment is being used for this disease but there is drug called Nitisinone which has shown some results in treating this disease^[9],^[10]. Most commonly patient presents with symptoms of arthropathy and it is usually diagnosed at the time of surgery that it is ochronotic arthropathy. Early diagnosis of ochronosis is very crucial to avoid complication such as tendon rupture and cardiorespiratory complications during surgery ^[7]. In our case, the patient was presented with fracture neck of femur, chronic back, and knee pain which were thought to be age related degenerative changes and treatment plan was made to do bipolar hemiarthroplasty. Diagnosis was made after finding brown-black cartilage of femur head and confirming it with complete history, clinical examinations, and investigations for alkaptonuria. Hence, surgeons and anesthetics both should take history with high suspicion to differentiate other cause of arthropathy from ochronosis to avoid complication during surgery. Arthropathy should also be differentiated from seronegative arthritis so that treatment plan can be made accordingly.

We report this case to show coexistence of scoliosis, knee arthropathy, and fracture neck of femur in patients with ochronosis. This arthropathy should be differentiated preoperatively from other common arthropathy causes and treated accordingly. Common clinical findings of ochronosis such as pigmentation of sclera, ear, and nose cartilage should never be missed while examining patient.

Any patient come with arthropathy and scoliosis should be assessed and investigated for ochronosis. After making diagnosis fracture, the patient should be evaluated for respiratory and cardiac involvement of ochronosis to avoid complications during surgery. Surgical approach can be challenging in such patients as tendons and capsule tissue is brittle and stiff, it can easily be ruptured or avulsed.