Unique Variant of Cerebrotendinous Xanthomatosis Presenting With Eyelid Involvement Due to Heterozygous CYP7A1 and SLC10A1 Gene Mutations

Abstract

We report a case of a novel phenotypic variant of cerebrotendinous xanthomatosis (CTX) with an adult onset, caused by 2 coexisting mutations involving the CYP7A1 and SLC10A1 genes. A 49-year-old male patient presented with eyelid xanthomatosis associated with dermatochalasis, nystagmus, right-sided paresis with hyperreflexia and atypical parkinsonism. Bilateral xanthomatous plaques involving both Achilles tendons were subsequently detected. Histopathology of the eyelids demonstrated marked diffuse stromal infiltrates of prominent foamy histiocytes. His lipid profile showed only a slightly elevated non-high density lipoprotein cholesterol level but with normal cholesterol and cholestanol levels. By contrast, classic CTX characteristically demonstrates a markedly elevated cholestanol and a mutation involving the CYP27A1 gene for enzyme cholesterol 27-hydroxylase. Unexpectedly, molecular studies on this patient revealed a heterozygous mutation involving 2 different genes, namely, CYP7A1 and SLC10A1 genes. The CYP7A1 gene encodes for the enzyme cholesterol 7a-hydroxylase, which is a ratelimiting enzyme in the cholesterol degradation. The SLC10A1 Na + / taurocholate cotransporter gene is involved in the enterohepatic circulation of bile acids and for the hepatocyte uptake of cholesterol. We are the first to report an unusual case of an adult-onset CTX manifesting with eyelid xanthomas associated with an uncharacteristic lipid profile and a detection of novel heterozygous mutations of CYP7A1 and SLC10A1 genes in this neurocutaneous syndrome.