Tuberous xanthomas in sitosterolemia

Sitosterolemia: Four Cases of an Uncommon Cause of Hemolytic Anemia (Mediterranean Stomatocytosis with Macrothrombocytopenia)

Sitosterolemia is a rare autosomal recessively inherited lipid metabolic disorder that is characterized by hyper absorption of plant sterols from the intestinal mucosa leading to toxic levels in the blood. Four patients of age ranging from 11 to 29 years presented to the outpatient department with clinical features of hemolytic anemia. There were no features of hypercholesterolemia in any of the patients. Peripheral smear examination of all four patients showed stomatocytes and macrothrombocytopenia. Qualitative testing for plant sterols was performed in one case. Next generation sequencing revealed a compound heterozygous mutation in ABCG5 gene (c.1222C>T and c.1255C>T) in one case and homozygous mutations in ABCG5 gene (c.727C>T), (c.332G>A (p.G111E)), (c.1222C>T) in the other three cases. Ezetimibe (10 mg/day) was administered in one case, with complete resolution of symptoms. All patients were advised a low plant sterol diet and regular monitoring of hemoglobin and lipid profile. Our cases highlight a rare but important cause of hemolytic anemia that can be suspected from careful peripheral blood examination but only conclusively established by molecular genetic diagnosis.

Numerous intertriginous xanthomas in infant: A diagnostic clue for sitosterolemia

Sitosterolemia is a very rare autosomal recessive lipoprotein metabolic disorder caused by homozygous or compound heterozygous mutations in one of the two adenosine triphosphate-binding cassette transporter genes, ABCG5 and ABCG8. Sitosterolemia is clinically characterized by xanthomas and atherosclerosis, arthritis, fever, hemolysis and macrothrombocytopenia even in early childhood. We described a 16-month-old girl, who had numerous yellowish-brown intertriginous xanthomas along the skin creases on the extremities with severe hypercholesterolemia and elevated plant sterol levels. Histopathologically, xanthoma showed aggregation of foam cells in the dermis with a zone of mucin deposits in the dermal papilla. Electron microscopy showed numerous membrane-bound lipid droplets and multivesicular lipid bodies in the foam cells, a round cell containing lipid droplets in the basal cell layer and abundant mucin deposits just beneath the basal lamina. Diagnosis of sitosterolemia was confirmed by DNA sequencing showing compound heterozygosity for previously reported missense mutations in exon 9 of ABCG5. Infants presenting with multiple xanthomas should be investigated for sitosterolemia, if there is no family history of dyslipidemia.

Sitosterolemia: a new mutation in a Mediterranean patient

Sitosterolemia is a rare autosomal recessive disorder characterised by a high plasma level of sterols. A homozygous mutation or the compound heterozygous mutation in the ABCG5 gene or the ABCG8 gene leads to a complete loss of function of the ATP-binding cassette (ABC) heterodimer transporter G5-G8, which is localised to the apical membrane of enterocytes and hepatocytes. In enterocytes, this complex rejects plant sterols, whereas it promotes their excretion into the bile in the liver. The loss of function of the transporter ABCG5-G8 leads to a high concentration of plasma plant sterols and to its accumulation in tissues. We report here a new mutation of sitosterolemia in a 59-year-old woman with xanthelasma, precocious atherosclerosis, haemolytic anemia and macrothrombocytopenia. She was treated before the availability of Ezetimibe wich is now the gold standard treatment of this disease.

Xanthomas: clinical and pathophysiological relations

BACKGROUND

Xanthomas are well circumscribed lesions in the connective tissue of the skin, tendons or fasciae that predominantly consist of foam cells; these specific cells are formed from macrophages as a result of an excessive uptake of low density lipoprotein (LDL) particles and their oxidative modification.

RESULTS

Until recently, xanthelasma was considered to be only a cosmetic lesion; however, according to the results of recent prospective studies it is connected with an increased cardiovascular risk and reduced average lifespan. Pathogenetic mechanisms involved in the development of xanthomas resemble early stages of atherogenesis. In clinical practice, xanthomas can signalise various congenital or acquired dyslipidemias. The most prevalent form of xanthomas is xanthelasma palpebrarum. Tendinous and tuberous xanthomas are typical for autosomal dominant hypercholesterolemia, as well as for some rare conditions, such as cerebrotendinous xanthomatosis and familial β-sitosterolemia. In patients with familial hypercholesterolemia, the presence of tendinous xanthomas has been shown to be associated with a two to four times higher risk for cardiovascular disease. Eruptive xanthomas are skin manifestations of a severe hypertriglyceridemia and implicate an elevated risk for acute pancreatitis or type 2 diabetes mellitus. Xanthoma striatum palmare is pathognomic for primary dysbetalipoproteinemia, whereas diffuse plane xanthomas are frequently associated with paraproteinemia and lymphoproliferative disorders.

CONCLUSION

Thorough familiarity with the clinical presentation of xanthomas helps in the diagnosis and follow-up of different forms of dyslipidemia. Moreover, xanthelasma palpebrarum, the most prevalent form of xanthomas, is connected with increased risk of atherothrombotic disease independently of conventional cardiovascular risk factors. To fully understand the pathogenesis, further experimental and clinical research is required.

Non-cholesterol sterols and cholesterol metabolism in sitosterolemia

Sitosterolemia (STSL) is a rare autosomal recessive disease, manifested by extremely elevated plant sterols (PS) in plasma and tissue, leading to xanthoma and premature atherosclerotic disease. Therapeutic approaches include limiting PS intake, interrupting enterohepatic circulation of bile acid using bile acid binding resins such as cholestyramine, and/or ileal bypass, and inhibiting intestinal sterol absorption by ezetimibe (EZE). The objective of this review is to evaluate sterol metabolism in STSL and the impact of the currently available treatments on sterol trafficking in this disease. The role of PS in initiation of xanthomas and premature atherosclerosis is also discussed. Blocking sterols absorption with EZE has revolutionized STSL patient treatment as it reduces circulating levels of non-cholesterol sterols in STSL. However, none of the available treatments including EZE have normalized plasma PS concentrations. Future studies are needed to: (i) explore where cholesterol and non-cholesterol sterols accumulate, (ii) assess to what extent these sterols in tissues can be mobilized after blocking their absorption, and (iii) define the factors governing sterol flux.

Miscellaneous non-inflammatory musculoskeletal conditions. Rare thesaurismosis and xanthomatosis

The focus will be on xanthomatosis, a tissue danger signal which needs to be recognized by the clinician, and its relationship with monogenetic lipoprotein disorders (cholesterol, triglycerides), bile acid and sterol metabolism, particularly on metabolic pathways and genetics as well as on musculoskeletal and cardiovascular involvement, and their implications for clinical management. The critical question is to assess coronary heart disease risk, requiring correct identification of the pattern of lipoprotein disorders and of the causes (primary or secondary). Familial hypercholesterolemia must be suspected in adults and children with raised total cholesterol, especially when there is a personal or a family history of premature coronary heart disease, usually requiring potent statins to achieve adequate LDL-cholesterol lowering, even if we do not know safety of long-term therapy and whether treatments of dyslipidemia early in life prevent cardiovascular diseases in adulthood. Cerebrotendinous xanthomatosis is a treatable disease and must be suspected if there is a history of infantile chronic diarrhea and/or juvenile cataracts, even in the absence of tendon xanthomas. Current evidence for the prevention and screening, diagnosis, and treatment of dyslipidemia are available for the clinicians.

Liver disease associated with canalicular transport defects: current and future therapies

Bile formation at the canalicular membrane is a delicate process. This is illustrated by inherited liver diseases due to mutations in ATP8B1, ABCB11, ABCB4, ABCC2 and ABCG5/8, all encoding hepatocanalicular transporters. Effective treatment of these canalicular transport defects is a clinical and scientific challenge that is still ongoing. Current evidence indicates that ursodeoxycholic acid (UDCA) can be effective in selected patients with PFIC3 (ABCB4 deficiency), while rifampicin reduces pruritus in patients with PFIC1 (ATP8B1 deficiency) and PFIC2 (ABCB11 deficiency), and might abort cholestatic episodes in BRIC (mild ATP8B1 or ABCB11 deficiency). Cholestyramine is essential in the treatment of sitosterolemia (ABCG5/8 deficiency). Most patients with PFIC1 and PFIC2 will benefit from partial biliary drainage. Nevertheless liver transplantation is needed in a substantial proportion of these patients, as it is in PFIC3 patients. New developments in the treatment of canalicular transport defects by using nuclear receptors as a target, enhancing the expression of the mutated transporter protein by employing chaperones, or by mutation specific therapy show substantial promise. This review will focus on the therapy that is currently available as well as on those developments that are likely to influence clinical practice in the near future.

Sitosterol xanthomatosis

BACKGROUND

Sitosterolaemia is a lipid disorder in which plasma plant sterol levels are extremely elevated. Sitosterolaemia is clinically characterized by tuberous and tendon xanthomas, premature vascular disease and arthritis.

OBJECTIVE

To report a case of sitosterolaemia diagnosed by cutaneous manifestations and to review this rare disease.

METHODS

We report the case of a 60-year-old woman who presented with cutaneous xanthomas, arterial hypertension and polyarthralgias. The patient had had hypercholesterolaemia for many years without reduction of serum cholesterol, despite treatment with fenofibrate.

RESULTS

Ezetimibe therapy was started, decreasing sitosterol plasmatic levels and tuberous xanthomas after 3 months of treatment.

CONCLUSION

It is important to detect levels of sitosterol in plasma in patients with premature vascular disease, presence of xanthomas, and uncontrolled hypercholesterolaemia. Ezetimibe therapy is effective.

Intestinal cholesterol absorption inhibitor ezetimibe added to cholestyramine for sitosterolemia and xanthomatosis

Sitosterolemia is a rare, recessively inherited disorder characterized by increased absorption and delayed removal of noncholesterol sterols, which is associated with accelerated atherosclerosis, premature coronary artery disease, hemolysis, and xanthomatosis. Treatments include low-sterol diet and bile salt-binding resins; however, these often do not reduce the xanthomatosis. We examined the effects of the intestinal cholesterol/phytosterol transporter inhibitor ezetimibe added to cholestyramine in a young female patient with sitosterolemia and associated xanthomatosis. The patient was an 11-year-old female with sitosterolemia presenting with prominent xanthomas in the subcutaneous tissue of both elbows who was receiving treatment with cholestyramine 2 g once daily. Bilateral carotid bruits were audible, and a grade II/VI systolic murmur was detected at the left upper sternal border. She also had a low platelet count of 111,000/microL. Ezetimibe 10 mg once daily was added to the patient's ongoing cholestyramine regimen, and she was evaluated for 1 year. The patient followed an unrestricted diet during the 1-year treatment period. After 1 year of treatment with ezetimibe added to ongoing cholestyramine therapy, the patient's plasma sitosterol and campesterol levels decreased by approximately 50%. Her carotid bruits completely resolved, her systolic murmur diminished, and her platelet count rose to 268,000/microL. More remarkably, the tuberous xanthomas on her elbows had completely regressed. Ezetimibe added to ongoing low-dose cholestyramine therapy led to a marked improvement in plasma sterol concentrations, complete regression of xanthomatosis, resolution of carotid bruits, and improvement in cardiac murmur in a young female patient with sitosterolemia.

Sitosterolemia: a gateway to new knowledge about cholesterol metabolism

Sitosterolemia (OMIM 210250) is a rare, autosomal recessive lipid disorder initially described almost 30 years ago. The disease is characterized by elevated plasma levels of plant sterols due to increased intestinal absorption and reduced biliary secretion of neutral sterols. Patients with sitosterolemia are frequently hypercholesterolemic, and develop xanthomas and premature coronary heart disease (CHD). Hemolysis, arthralgias and arthritis are also frequently associated with the disorder. Recently, sitosterolemia has been revealed to be due to mutations in either of the two ATP-binding cassette (ABC) half-transporters. ABCG5 or ABCG8. These two genes are expressed almost exclusively in the liver and intestine, and are co-regulated by the nuclear hormone receptor, liver X receptor (LXR). Genetically modified mice, which express either high levels or no ABCG5 and ABCG8 have been developed. Analyses of these mice confirm that these two transporters play key roles in regulating the absorption of dietary and biliary sterols, and in mediating the excretion of neutral sterols from the liver to the bile. The elucidation of the gene defects responsible for sitosterolemia provides potential therapeutic targets for the treatment of hyperlipidemias in the general population.

Plexiform xanthomatous tumor: a report of 20 cases in 12 patients

We present 12 patients with 20 plexiform xanthomatous tumors (PXTs). All patients were male. Patient ages ranged from 20 to 59 years (mean 45 years). Clinical information was available for 11 (92%) patients. Only one patient with markedly elevated cholesterol levels had a family history of hypercholesterolemia; none of the others had a family or personal history of diabetes mellitus, hypercholesterolemia, or hyperlipoproteinemia. Three patients had markedly elevated serum triglyceride levels. The tumors were solitary in seven patients and multiple in five patients: three patients had two tumors, one presented had three, and one had four. PXTs were located on the knee (n = 8), elbow (n = 5), foot or hand (n = 3), and one each on the Achilles tendon, buttock, toe, and back. PXT was white to yellow in color and ranged in size from 0.7 to 5 cm (mean 2.7 cm). The tumors were located in the dermis and subcutis, had a distinctive plexiform arrangement, and were composed of various admixtures of uniform epithelioid and xanthomatous cells. All tumors in patients with solitary or multiple lesions had a plexiform architecture. Most of the nodules of the plexiform pattern of PXTs measured 0.5-2 mm. Rarely cholesterol clefts, necrosis, sparse inflammation, and multinucleated Touton giant cells were present. In two patients with multiple tumors, the PXT completely lacked the xanthoma cells and thus resembled an epithelioid lesion. Immunohistochemically, all lesions were KP1 (CD68) and vimentin positive and lysozyme, S-100 protein, HMB-45, epithelial membrane antigen, cytokeratins, factor VIIIrag, CD34, muscle-specific actin, alpha-smooth muscle actin, desmin (D33), desmin (Der-11), chromogranin, synaptophysin, neurofilament protein, and glial fibrillary acidic protein negative. Two patients with multiple lesions noted recurrences over 10 years. With the exception of one patient who died of an unknown cause, all 10 patients with follow-up were alive, some with residual disease, over a mean of 9 years (range 1-25 years). Some PXTs may represent a morphologic variant of tuberous or tendinous xanthoma, yet its exclusive occurrence in men, absence of personal/familial hyperlipemia/hypercholesterolemia in some patients, and relative paucity of inflammation and cholesterol clefts may make this a distinctive entity.