An adult male with progressive spastic paraparesis and gait instability

Rapidly progressive dementia and intractable diarrhea: a teaching case report and a systematic review of cognitive impairment in Whipple’s disease

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Supplementary Information

Cerebrotendinous Xanthomatosis: Molecular Pathogenesis, Clinical Spectrum, Diagnosis, and Disease-Modifying Treatments

Cerebrotendinous xanthomatosis (CTX) is an autosomal recessive lipid storage disorder caused by mutations in the CYP27A1 gene, which encodes the mitochondrial enzyme sterol 27-hydroxylase. Decreased sterol 27-hydroxylase activity results in impaired bile acid synthesis, leading to reduced production of bile acids, especially chenodeoxycholic acid (CDCA), as well as elevated serum cholestanol and urine bile alcohols. The accumulation of cholestanol and cholesterol mainly in the brain, lenses, and tendons results in the characteristic clinical manifestations of CTX. Clinical presentation is characterized by systemic symptoms including neonatal jaundice or cholestasis, refractory diarrhea, juvenile cataracts, tendon xanthomas, osteoporosis, coronary heart disease, and a broad range of neuropsychiatric manifestations. The combinations of symptoms vary from patient to patient and the presenting symptoms, especially in the early disease phase, may be nonspecific, which leads to a substantial diagnostic delay or underdiagnosis. Replacement of CDCA has been approved as a first-line treatment for CTX, and can lead to biochemical and clinical improvements. However, the effect of CDCA treatment is limited once significant neuropsychiatric manifestations are established. The age at diagnosis and initiation of CDCA treatment correlate with the prognosis of patients with CTX. Therefore, early diagnosis and subsequent treatment initiation are essential.

c.1263+1G>A Is a Latent Hotspot for CYP27A1 Mutations in Chinese Patients With Cerebrotendinous Xanthomatosis

Background

Cerebrotendinous xanthomatosis (CTX) is an autosomal recessive disorder of bile acid synthesis caused by mutations in the CYP27A1 gene. CTX is an underdiagnosed and potentially treatable disease, thus a detailed appreciation of the phenotypic spectrum and genetic characteristics are crucial for early diagnosis and treatment.

Objectives and Methods

Four CTX families with mutations in the CYP27A1 gene were enrolled in our study. We investigated the clinical characteristics and molecular genetic features of the probands with CTX. Genetic analysis was performed for detecting gene variants. Sanger sequencing and segregation analysis were conducted for haplotype analysis.

Results

All the four probands were compound heterozygote for two CYP27A1 variants, including one mutation in c.1263+1G>A (intron 7) splice site, two novel likely pathogenic mutations (c.255+1G>T and c.1561dupA) and three pathogenic mutations including c.379C>T, c.1263+1G>A and c.1537C>T previously reported. All of the subjects presented with spastic paraparesis. The other common clinical features included ataxia, childhood-onset diarrhea, cataracts, intellectual disability, tendinous xanthomas and dentate nuclei signal alterations at MRI.

Conclusion

Two novel likely pathogenic mutations (c.255+1G>T and c.1561dupA) were reported in our study. The 1263+1G>A mutation was commonly seen in Chinese reported case series (7/25, 28%) and could be a latent hotspot for Chinese CTX mutations. Our study expanded the mutation spectrum of CYP27A1 gene and provide an insightful view of the phenotypic spectrum and genetic characteristics to help early diagnosis and treatment with to improve neurologic dysfunction.

Epidemiology, diagnosis, and treatment of cerebrotendinous xanthomatosis (CTX)

Cerebrotendinous xanthomatosis (CTX) is a rare autosomal recessive disorder of bile acid synthesis caused by mutations in the cytochrome P450 CYP27A1 gene that result in production of a defective sterol 27-hydroxylase enzyme. CTX is associated with abnormally high levels of cholestanol in the blood and accumulation of cholestanol and cholesterol in the brain, tendon xanthomas, and bile. Hallmark clinical manifestations of CTX include chronic diarrhea, bilateral cataracts, tendon xanthomas, and neurologic dysfunction. Although CTX is a rare disorder, it is thought to be underdiagnosed, as presenting signs and symptoms may be nonspecific with significant overlap with other more common conditions. There is marked variability in signs and symptoms, severity, and age of onset between patients. The disease course is progressive and potentially debilitating or fatal, particularly with respect to neurologic presentations that can include intellectual disability, autism, behavioral and psychiatric problems, and dementia, among others. Treatment with chenodeoxycholic acid (CDCA; chenodiol) is the current standard of care. CDCA can help restore normal sterol, bile acid, bile alcohol, and cholestanol levels. CDCA also appears to be generally effective in preventing adverse clinical manifestations of the disease from occurring or progressing if administered early enough. Improved screening and awareness of the condition may help facilitate early diagnosis and treatment.