A homozygous mutation in a Chinese man with Crigler-Najjar syndrome type II and a family genetic analysis

OBJECTIVE: To investigate the family genetic background of a 22-year-old man with Crigler-Najjar syndrome type II (CN-II). METHODS: After the proband (patient) with CN-II was diagnosed by liver function tests, a low calorie intake test and an oral phenobarbital enzyme-induction trial, blood samples were collected from 11 family members for identifying DNA gene groups. Exons 1-5 of the UGT1A1 gene were amplified by polymerase chain reaction (PCR) and mutations of the UGT1A1 gene were screened by a direct DNA sequencing. RESULTS: The serum unconjugated bilirubin increased in the proband from 156.4 micromol/L to 243.5 micromol/L after he started a low calorie intake, and it decreased to 51.8 micromol/L within a month of taking oral phenobarbital daily. Both functional tests and ultrasonographic images of the liver were normal except for the unconjugated hyperbilirubinemia. A missense mutation of Tyr486Asp at exon 5 in the UGT1A1 gene and a homozygous mutation were confirmed in the proband. Heterozygous mutations were found in his parents, his younger sister and three great-uncles, while no mutation of the UGT1A1 gene was detected in the remaining four family members. CONCLUSION: A missense mutation of Tyr486Asp is considered to be the cause of the CN-II in this patient. It is a recessive trait that is autosomally inherited in this family. No influence of the mutation was found on the response elements for phenobarbital in the promoter region.     

The presence of a microsomal UDP-glucuronyl transferase for bilirubin in homozygous jaundiced Gunn rats and in the Crigler-Najjar syndrome

The infusion of a closely related derivative of bilirubin, its dimethyl diester (DME), into jaundiced (jj) Gunn rats were associated with biliary excretion of mono- and diglucuronides of bilirubin. In vitro incubation of DME with liver microsomes from jj rats demonstrated sequential demethylation and glucuronidation of DME. Liver microsomes from a patient with the Crigler-Najjar syndrome were unable to form glucuronides of bilirubin in vitro unless DME was used as substrate. The results suggest that the deficiency in Gunn rats and in the Crigler-Najjar syndrome may be due to a structural defect in the microsomal matrix which contains glucuronyl transferase. This interpretation envisions a microenvironment of the transferase enzyme which is either impermeable to bilirubin or induces conformational changes which interfere with glucuronidation.     

Characteristic cardiovascular manifestation in homozygous and heterozygous familial hypercholesterolemia

BACKGROUND: The aortic valve dysfunction of patients with homozygous familial hypercholesterolemia (FH) suggests that hypercholesterolemia affects not only coronary arteries but also the aortic valve. We studied the aortic root of patients with homozygous FH and those of patients with heterozygous FH to characterize the premature atherosclerotic lesions by using histopathologic specimens. METHODS AND RESULTS: The aortic roots of 10 patients with homozygous FH, age 9 to 58 years, were studied by cardiac catheterization with several angiographies. The aortic roots of 39 patients with heterozygous FH under age 60 years were also examined for aortic and mitral valvular functions by color Doppler echocardiography, and 30 normocholesterolemic patients with coronary artery disease were examined as control subjects. In addition, in 22 patients with FH and 20 control subjects, the internal diameter of the aortic annulus and the aortic ridge in cardiac cycles were measured. Of the 10 homozygotes with FH, 8 patients had aortic regurgitation demonstrated by aortography; 3 of them showed significant transvalvular pressure gradients. Stenotic changes of coronary ostia were observed in 8 of the 10 homozygotes with moderate coronary atherosclerosis. Of the 39 heterozygotes with FH, 10 patients had aortic regurgitation shown by Doppler echocardiography, as did only 1 of the 30 control subjects (P <.05). The average diameter and distensibility of the ascending aorta were significantly reduced in the heterozygotes compared with the control subjects. The surgically resected cusp specimens of aortic valves obtained from 1 homozygous and 1 heterozygous patient showed significant thickening of the cusp with foam cell infiltration. CONCLUSIONS: Premature atherosclerosis in FH had a characteristic distribution, affecting the aortic root dominantly. The involvement of the aortic valve indicating "hypercholesterolemic valvulopathy" was a peculiar feature of FH, especially its homozygous form, but was reminiscent of ubiquitous processes caused by hypercholesterolemia.     

Investigation of the molecular basis of the genetic deficiency of UDP-glucuronosyl-transferase in Crigler-Najjar syndrome

Summary Liver biopsy samples were obtained from eight Crigler-Najjar patients. Bilirubin UDPGT activity, assayed by a microassay with HPLC analysis, was not detectable in type I livers, and low levels (9–26% of controls) of monoglucuronide conjugates only were observed in type II livers. 1-Naphthol UDPGT activity was normal in most patients, where membrane integrity was maintained by correct sample procurement and preparation. Our data on type II livers suggest that a defect in UDPGA transport is an unlikely cause of the hyperbilirubinaemia, but reduced affinity for UDPGA was observed in one sample. Analysis of four patient liver samples by immunoblot analysis revealed the heterogeneous nature of this inherited disease within the patient population, and one sample where 1-naphthol UDPGT activity was considerably reduced appeared to correlate with the non-detection of a phenol UDPGT protein. Progress towards a molecular genetic diagnosis of Crigler-Najjar syndromes is discussed.     

Disturbed homeostasis in sodium-restricted mice heterozygous and homozygous for aldosterone synthase gene disruption

We have determined that differences in expression of aldosterone synthase (AS) affect responses to a low-salt diet. In AS-null mice (AS(-/-)), but not in wild-type, low salt significantly decreased plasma sodium and increased potassium. The increased urine volume (1.5xwild-type) and decreased urine osmolality (0.7xwild-type), present in AS(-/-) mice on normal salt, became more severe (2.3xwild-type and 0.5xwild-type) on low salt, but neither changed in wild-type. In both genotypes, plasma vasopressin was similar on normal and low salt, and desmopressin injection significantly increased urine osmolality. Renal mRNA levels for aquaporin 1 and 3 were unchanged by genotype or diet and epithelial sodium channel and Na(+)-K(+)-2Cl(-)-cotransporter by genotype. In AS(-/-) mice, aquaporin 2 mRNA increased on normal salt, whereas Na(+)Cl(-)-cotransporter and cortex K(+) channel mRNAs decreased on both diets. The low blood pressure of AS(-/-) mice was decreased further by low salt, despite additional increases in renin, intrarenal arterial wall thickness, and macula densa cyclogenase-2 mRNA. In AS(+/-) mice on normal salt, adrenal AS mRNA was slightly decreased (0.7xwild-type), but blood pressure was normal. On low salt, their blood pressure was less than wild-type (101+/-2 mm Hg versus 106+/-2 mm Hg), even though renin mRNA increased to 2xwild-type. We conclude that aldosterone is critical for urine concentration and maintenance of blood pressure and even a mild reduction of AS expression makes blood pressure sensitive to low salt, suggesting that genetic differences of AS levels in humans may influence how blood pressure responds to dietary salt.     

Prostate visualization studies in males homozygous and heterozygous for 5 alpha-reductase deficiency.

Male pseudohermaphrodites with 5 alpha-reductase deficiency have ambiguous genitalia and nonpalpable prostates on rectal examination, suggesting the dihydrotestosterone dependency of these structures. To clearly delineate the status of the prostate, male pseudohermaphrodites with 5 alpha-reductase deficiency had transrectal sonography of the prostate performed, and the results were compared to that of age-matched male controls. In six male pseudohermaphrodites, magnetic resonance imaging studies of the prostate were also performed. Heterozygote fathers also had transrectal sonography of the prostate performed and the results compared to age-matched controls. The prostates of the male pseudohermaphrodites appeared as platelike soft tissue structures posterior to the urethra on both prostatic ultrasound and magnetic resonance imaging. Prostatic volume, as determined on prostatic ultrasound by two different methods, was significantly smaller (approximately one-tenth) than the volume of age-matched controls. Transurethral ultrasound guided biopsy of the prostate in two affected subjects revealed stromal tissue. These results correlate with undetectable prostate-specific antigen in affected subjects, suggesting atrophic epithelium or lack of epithelial differentiation. This study demonstrates the dihydrotestosterone dependence of the prostate for normal differentiation and growth. The presence of some prostatic tissue in the male pseudohermaphrodites may be due to the fact that there is a decrease and not an absence of 5 alpha-reductase activity, and/or that the increased level of testosterone in subjects with this condition partially compensates for the decreased level of dihydrotestosterone. There was no difference, however, in prostate size between heterozygous fathers and age-matched control males. The heterozygote fathers had dihydrotestosterone production sufficient for normal prostate growth and development.     

Responsiveness to phenobarbital in an adult with Crigler-Najjar disease associated with neurological involvement and skin hyperextensibility

We present the case of a 23-yr-old man who had had since birth marked and sustained unconjugated non-hemolytic hyperbilirubinemia and who had had several attacks of grand mal seizures. Analysis of serum bilirubin by diazoreactive methods showed serum levels of unconjugated bilirubin as high as 445 mumol/L that were not affected by phenobarbital administration. However, analysis of serum bile pigments by high-pressure liquid chromatography demonstrated marked decrease of unconjugated bilirubin after phenobarbital treatment (from 432.4 mumol/L to 291.0 mumol/L) associated with slight increase of bilirubin monoconjugates and disconjugates (from 0.25 mumol/L to 0.42 mumol/L). Furthermore, in the past few years the patient had exhibited striking skin hyperextensibility and diaphragm eventration. This case confirms that alkaline methanolysis-high-pressure liquid chromatography is the most reliable method for assessment of serum fraction bilirubin levels; that clinical parameters such as neurological signs do not unequivocally discriminate between type I and II Crigler-Najjar disease and that response to phenobarbital treatment remains the main diagnostic tool.     

Persistent splenomegaly in an adult female with homozygous sickle cell anemia

Sickle cell anemia (SCA) is associated with repeated episodes of erythrostasis in the spleen, which lead to thrombosis and infarction of the spleen resulting in "autosplenectomy" which is usually complete by 8 years of age.

We present a case of a 22-year-old female who presented with complaints of fever, bone pain and joint swelling. On examination she had pallor, icterus and moderate splenomegaly. Her hemoglobin was 7.5 g/dl. Peripheral smear showed many sickled red cells. Slide test for sickling was positive with 2% sodium metabisulphite. Hemoglobin electrophoresis revealed a single band in the hemoglobin S, D, and G region. No band was seen in the HbA & HbA₂ region. HbF level was 0%. USG showed an enlarged spleen with few defined hypoechoeic lesion.

We present this case because of rarity of association of homozygous SCA with splenomegaly in this age group, the confusion that echogenic lesions in spleen can create and to emphasize the risk of sequestration crises, which remains in such cases.     

Persistent splenomegaly in an adult female with homozygous sickle cell anemia

Sickle cell anemia (SCA) is associated with repeated episodes of erythrostasis in the spleen, which lead to thrombosis and infarction of the spleen resulting in "autosplenectomy" which is usually complete by 8 years of age.We present a case of a 22-year-old female who presented with complaints of fever, bone pain and joint swelling. On examination she had pallor, icterus and moderate splenomegaly. Her hemoglobin was 7.5 g/dl. Peripheral smear showed many sickled red cells. Slide test for sickling was positive with 2% sodium metabisulphite. Hemoglobin electrophoresis revealed a single band in the hemoglobin S, D, and G region. No band was seen in the HbA & HbA(2) region. HbF level was 0%. USG showed an enlarged spleen with few defined hypoechoeic lesion.We present this case because of rarity of association of homozygous SCA with splenomegaly in this age group, the confusion that echogenic lesions in spleen can create and to emphasize the risk of sequestration crises, which remains in such cases.