Current Diagnosis and Management of Tangier Disease

Abstract

Tangier disease is a genetic disorder characterized by an absence or extremely low level of high-density lipoprotein (HDL)-cholesterol (HDL-C). It is caused by a dysfunctional mutation of the ATP-binding cassette transporter A1 (ABCA1) gene, the mandatory gene for generation of HDL particles from cellular cholesterol and phospholipids, and it appears in an autosomal recessive hereditary profile. To date, 35 cases have been reported in Japan and 109 cases outside Japan. With dysfunctional mutations in both alleles (homozygotes or compound heterozygotes), the HDL-C level is mostly less than 5 mg/dL and there is 10 mg/dL or less of apolipoprotein A-I (apoA-I), the major protein component of HDL. In patients with Tangier disease, major physical findings are orange-colored pharyngeal tonsils, hepatosplenomegaly, corneal opacity, lymphadenopathy, and peripheral neuropathy. Although patients tend to have decreased low-density lipoprotein (LDL)-cholesterol (LDL-C) levels, premature coronary artery disease is frequently observed. No specific curative treatment is currently available, so early identification of patients and preventing atherosclerosis development are crucial. Management of risk factors other than low HDL-C is also important, such as LDL-C levels, hypertension and smoking. Additionally, treatment for glucose intolerance might be required because impaired insulin secretion from pancreatic beta cells has occasionally been reported.

Keywords: ABCA1; Atherosclerosis; Cholesterol efflux; HDL; Orange tonsil; Reverse cholesterol transport; Tangier disease.

Fig.1.Roles of ABCA1 in formation of HDL particles, reverse cholesterol transport and pathogenesis of Tangier disease

Fig.2. Orange-colored tonsils observed in male patient with Tangier disease in his 50s

Arrow heads indicate palatine tonsil (left panel) and lingual tonsil (right panel). Reproduced from reference [8].

Fig.3. Abdominal CT scan of splenomegaly in female patient with Tangier disease in her 40s

The photo was kindly provided by one of the co-authors, Prof. Yasushi Ishigaki (Iwate Medical University).

Fig.4. Advanced systemic atherosclerotic lesions in male patient with Tangier disease in his 50s

Arrows indicate stenosis or occlusion of the artery. A: left coronary artery, B: right coronary artery, C: brachiocephalic artery, D: left iliac artery, E: right external iliac artery [8].

Fig.5. Differential diagnosis flow chart for hypo-HDL-cholesterolemia