Clinically probable alkaptonuria-associated ochronosis presenting as multilevel cervical disc herniation with myeloradiculopathy managed by three-level C4-7 anterior cervical discectomy and fusion: a case report.

Background/introduction: Alkaptonuria (AKU) is a rare disorder of tyrosine metabolism characterized by homogentisic acid accumulation and ochronotic pigment deposition in connective tissues. Spinal involvement is common, but cervical disc herniation with clinically significant myeloradiculopathy requiring multilevel anterior surgery is infrequently reported. A distinctive operative hallmark is the diffusely dark ("black") intervertebral disc/nucleus pulposus, which may be the first clue to the underlying diagnosis. Case presentation: An adult patient presented with 6 months of progressive neck pain and bilateral upper-limb numbness/pain, most prominent in the lateral aspect of the right upper arm and involving all fingers of both hands, accompanied by gait disturbance described as a "cotton-like sensation." Neurologic examination demonstrated long-tract signs consistent with cervical myelopathy and superimposed radiculopathy. Cervical MRI showed multilevel disc degeneration with posterior protrusions, ventral dural sac compression, and intramedullary signal change, with the most severe stenosis at C4/5, C5/6, and C6/7. Interventions: Given progressive myeloradiculopathy with multilevel anterior compression, the patient underwent three-level C4-7 anterior cervical discectomy and fusion (ACDF) to achieve ventral decompression and segmental stabilization. Intraoperatively, the intervertebral discs and nucleus pulposus were diffusely black-pigmented, a gross appearance that strongly raised suspicion for ochronotic disc involvement. Representative disc material was collected for microbiological testing, which showed no bacterial or fungal growth. Because quantitative urinary homogentisic acid measurement and HGD genetic testing were not completed before manuscript preparation, the diagnosis was regarded as clinically probable rather than biochemically confirmed. Results/conclusions: Postoperatively, the patient showed early improvement in limb numbness and gait stability, and radiographs confirmed satisfactory implant position and cervical alignment. This case emphasizes that a "black disc" encountered during routine cervical discectomy should prompt immediate consideration of AKU/ochronosis, careful documentation and tissue sampling, and definitive metabolic testing (quantitative urinary homogentisic acid measurement, with HGD genetic testing when available). However, in the absence of biochemical or genetic confirmation, the intraoperative black-disc finding should be interpreted as a highly suggestive diagnostic clue rather than definitive proof of AKU. Standard cervical decompression and fusion principles remain effective for neurologic compromise, but recognition of a possible underlying metabolic disorder is essential for systemic evaluation and long-term surveillance.