Presentation
Gait instability and swelling along posterior aspect of ankle joint.
Patient Data
The Achilles tendon shows marked diffuse thickening with loss of concavity of its anterior margin with low T2 signal.
Bilateral dentate nuclei and deep cerebellar white matter hyperintense signal on T2WI with corresponding hypointense signal intensity on T1WI and FLAIR associated with focal increase signal intensity of the brainstem. Generalized age inappropriate cerebral and cerebellar atrophy.
Case Discussion
With a combined spectrum of clinical and radiological findings, a diagnosis of cerebrotendinous xanthomatosis (CTX) was made based on the clinical history of chronic gait instability, bilateral ankle swelling and juvenile cataracts, with brain MRI findings of bilateral cerebellar abnormal signal intensities, cerebral and cerebellar atrophy as well as ankle MRI of bilateral Achilles tendon xanthomas.
Differential diagnosis includes sitosterolemia and Marinesco‑Sjogren syndrome.
CTX mimics sitosterolemia as xanthomas are a clinical feature of both. Sitosterolemia is differentiated from CTX by absence of neurological symptoms and cataract formation.
CTX also resembles Marinesco‑Sjogren syndrome, which also presents with triad of cataract formation, ataxia and cognitive delay but the absence of tendon xanthomas and presence of scoliosis, short small bones of hand and feet reliably differentiate this disorder from CTX.
On neuroimaging alone, those disorders which exhibit hyperintensity of dentate nuclei on T2W images need to be differentiated from CTX. These include metronidazole toxicity and acutely decompensated maple syrup urine disease. These two disorders present with acute encephalopathy unlike CTX which has an insidious presentation.
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