Cerebrotendinous xanthomatosis (CTX) is a rare disease attributed to partial or complete loss of the enzyme sterol-27-hydroxylase leading to chenodeoxycholic acid and cholic acid production deficiency, and accumulation of sterol intermediates, mainly cholestanol, in plasma and in several other tissues. The clinical phenotype of CTX greatly varies among patients and includes tendon xanthomas, gallbladder stones, diarrhea, cataracts, and neurological abnormalities.1 The diagnostic identification typically is characterized by an elevated level of plasma cholestanol and identification of CYP27A1 gene variants. However, there is a great diversity of phenotypes of this pathology so it is often difficult to identify the disease, and underdiagnosis is frequent, but the treatment with chenodeoxycholic acid can prevent the unfavorable evolution of the disease.2 In his regard, a case of brain damage with absent tendon xanthomas has been described.3 We report here two cases of alteration of the CYP27A1 gene characteristic of CTX, without elevation of cholestanol in plasma and tendon, with extremely large Achilles tendon lesions but absence of other clinical manifestations typical of the disease.