Klaus Kruse

Phenotypic classification of male pseudohermaphroditism due to steroid 5α‐reductase 2 deficiency

Conversion of testosterone (T) to dihydrotestosterone (DHT) in genital tissue is catalysed by the enzyme 5 alpha-reductase 2, which is encoded by the SRD5A2 gene. The potent androgen DHT is required for full masculinization of the external genitalia. Mutations of the SRD5A2 gene inhibit enzyme activity, diminish DHT formation, and hence cause masculinization defects of varying degree. The classical syndrome, formerly described as pseudovaginal perineoscrotal hypospadias, is characterized by a predominantly female phenotype at birth and significant virilization without gynecomastia at puberty. We investigated nine patients with steroid 5 alpha-reductase 2 deficiency (SRD). Phenotypes, which were classified according to the severity of the masculinization defect, varied between completely female (SRD type 5), predominantly female (SRD type 4), ambiguous (SRD type 3), predominantly male with micropenis and hypospadias (SRD type 2), and completely male without overt signs of undermasculinization (SRD type 1). T/DHT-ratios were highly increased ( > 50) in the classical syndrome (SRD type 5), but variable in the less severe affected patients (SRD types 1-4) (14-35). Mutations in the SRD5A2 gene had been characterized using PCR-SSCP analysis and direct DNA sequencing. A small deletion was encountered in two patients, while all other patients had single base mutations which result in amino acid substitutions. We conclude that phenotypes may vary widely in patients with SRD5A2 gene mutations spanning the whole range from completely female to normal male without distinctive clinical signs of the disease. Hence, steroid 5 alpha-reductase deficiency should be considered not only in sex reversed patients with female or ambiguous phenotypes, but also in those with mild symptoms of undermasculinization as encountered in patients with hypospadias and/or micropenis. A classification based on the severity of the masculinization defect may be used for correlation of phenotypes with enzyme activities and genotypes, and for comparisons of phenotypes between different patients as the basis for clinical decisions to be made in patients with pseudohermaphroditism due to steroid 5 alpha-reductase 2 deficiency.

The clinical and molecular spectrum of androgen insensitivity syndromes

Androgen insensitivity syndromes (AIS) are due to end-organ resistance to androgenic steroids in males leading to defective virilization of the external genitalia. The phenotype encompasses a wide array of genital ambiguity and may range from completely female to undervirilized but unequivocally male with infertility. This disorder is caused by mutations of the androgen receptor and is an X-linked recessive trait. We have studied 47 patients with AIS and have characterized the underlying molecular abnormality in the androgen receptor gene. Twenty patients had complete AIS and twenty-seven had partial AIS. Of the latter, 11 were of predominantly female phenotypic appearance and gender was assigned accordingly, while 16 were raised as males. Within the group of complete AIS, two patients had gross deletions within the gene, one had a small deletion, and one had an insertion. In the other patients with complete AIS, as well as all individuals with partial AIS, single nucleotide substitutions within the coding region were detected, each leading to an amino acid alteration. Seven codons were involved in more than one mutation in different cases. In addition, in one patient with spinal and bulbar muscular atrophy, an elongation of a glutamine-repeat was characterized. We conclude that mutations in the androgen receptor gene may be present throughout the whole coding region. However, our study provides evidence that several mutational hot spots exist.

Functional assessment and clinical classification of androgen sensitivity in patients with mutations of the androgen receptor gene

Abstract In the genetic male, mutations of the androgen receptor (AR) gene cause phenotypes ranging from female to subfertile male. Binding assays on genital skin fibroblasts and DNA analysis alone provide incomplete information about receptor function. We used the sex hormone-binding globulin (SHBG) response to stanozolol as a measure of AR function and correlated the results with phenotypes which were classified according to the degree of defective masculinization. Of the 34 patients investigated, 9 had complete, and 14 had partial androgen insensitivity syndrome (AIS) with predominantly female, ambiguous, or predominantly male phenotype. Eleven subjects served as controls. Mutations were characterized using polymerase chain reaction-single strand conformation polymorphism analysis and direct DNA sequencing. DNA analysis revealed two major deletions, two minor defects leading to premature stop codons in exon 1, and 19 point mutations in the DNA- and hormone-binding domains of the AR gene. After stanozolol, SHBG remained unchanged in patients with complete AIS (102.0 ± 3.8 [SE]%; range 92.4%–129% of the initial value). The SHBG decrease was diminished in partial AIS with predominantly female (83.8% ± 1.7%; range 81.3%–87.0%), ambiguous (80.4% ± 4.4%, range 68.4%–89.1%), and predominantly male (mean 65.9% ± 4.9%, range 48.6%– 80.8%) phenotypes, and normal in controls (51.4% ± 2.1%, range 35.6%–62.1%). Differences between controls and each AIS group were statistically significant (P< < 0.05 – < 0.0001). A close correlation was found between the degree of undermasculinization (AIS phenotype) and the SHBG response. Conclusions The SHBG test provides functional information about the severity of the receptor defect in vivo and hence adds to the structural information provided by DNA analysis. It detects receptor defects due to mutations within the entire gene, including the DNA-binding domain, and is a rapid, simple, and cost effective procedure. It may provide useful information for the diagnosis and management of affected children.

Inherited and de novo androgen receptor gene mutations : investigation of single-case families

OBJECTIVE The objective of this study was to assess somatic and inherited androgen receptor gene mutations in families with only one affected individual. METHODS Molecular genetic analysis of the androgen receptor gene in DNA derived from blood leukocytes from 30 families with single-strand conformation analysis, direct sequencing, and restriction fragment analysis was performed. RESULTS In 22 families the mothers and all investigated grandmothers were heterozygous carriers. However, within the sisters and aunts, both heterozygous carriers and noncarriers were present. In eight families a de novo mutation was characterized. In three of these patients indication for somatic mosaicism was found. CONCLUSIONS De novo mutations occur at a high rate within the androgen receptor gene (8 of 30 = 26.7%); a high proportion (3 of 8) arise after the zygote stage. Thus only direct analysis of the underlying mutation of the androgen receptor gene in the proband and his or her family can provide the basis for genetic counseling.

Elevated 1,25-dihydroxyvitamin D serum concentrations in infants with subcutaneous fat necrosis

Two infants with subcutaneous fat necrosis had hypercalcemia that normalized during glucocorticoid treatment. The combination of hypercalcemia, normal concentration of 25-hydroxyvitamin D, an elevated concentration of 1,25-dihydroxyvitamin D, a suppressed parathyroid hormone level, and low-normal bone turnover indicated abnormal 1,25-dihydroxyvitamin D production with increased intestinal absorption of calcium. Unregulated production of 1,25-dihydroxyvitamin D by the granulomatous cells of fat necrosis may cause hypercalcemia.

Clinical and Molecular Spectrum of Somatic Mosaicism in Androgen Insensitivity Syndrome

We recently found that postzygotic de novo mutations occur at the expected high rate of an X-linked recessive mutation in androgen insensitivity syndrome. The resulting somatic mosaicism can be an important molecular determinant of in vivo androgen action caused by expression of the wild-type androgen receptor (AR). However, the clinical relevance of this previously underestimated genetic condition in androgen insensitivity syndrome has not been investigated in detail as yet. Here, we present the clinical and molecular spectrum of somatic mosaicism considering all five patients with mosaic androgen insensitivity syndrome, whom we have identified since 1993: Patient 1 (predominantly female, clitoromegaly), 172 TTA(Leu)/TGA(Stop); patient 2 (ambiguous), 596 GCC(Ala)/ACC(Thr); patient 3 (ambiguous), 733 CAG(Gln)/CAT(His); patient 4 (completely female), 774 CGC(Arg)/TGC (Cys); and patient 5 (ambiguous), 866 GTG(Val)/ATG(Met). Serum sex hormone binding globulin response to stanozolol, usually correlating well with in vivo AR function, was inconclusive for assessment of the phenotypes in all tested mosaic individuals. An unexpectedly strong virilization occurred in patients 1, 3, and 5 compared with phenotypes as published with corresponding inherited mutations and compared with the markedly impaired transactivation caused by the mutant ARs in cotransfection experiments. Only the prepubertal virilization of patients 2 and 4 matched appropriately with transactivation studies (patient 4) or the literature (patients 2 and 4). However, partial pubertal virilization in patient 4 caused by increasing serum androgens and subsequent activation of the wild-type AR could not be excluded. We conclude that somatic mosaicism is of particular clinical relevance in androgen insensitivity syndrome. The possibility of functionally relevant expression of the wild-type AR needs to be considered in all mosaic individuals, and treatment should be adjusted accordingly.

Loss of Renal Phosphate Wasting in a Child with Autosomal Dominant Hypophosphatemic Rickets Caused by a FGF23 Mutation

A girl with autosomal dominant hypophosphatemic rickets, presented with clinical, radiological and laboratory signs of rickets at the age of 11 months. She showed a good response to the treatment with low doses of oral phosphate and calcitriol. Surprisingly, she lost her renal phosphate wasting at the age of 8 years, indicating that the disturbed phosphate metabolism can be compensated by hormonal or other factors.

Hypoparathyroidism and deafness associated with pleioplasmic large scale rearrangements of the mitochondrial DNA : A clinical and molecular genetic study of four children with Kearns-Sayre syndrome

In four children with hypoparathyroidism and deafness as initial major manifestations of Kearns-Sayre syndrome, a unique pattern of mitochondrial DNA rearrangements was observed. Hypocalcemic tetany caused by PTH deficiency started between age of 6-13 y and was well controlled by small amounts of 1,25-(OH)2-cholecalciferol. Rearranged mitochondrial genomes were present in blood cells of all patients and consisted of partially duplicated and deleted molecules, created by the loss of 7813, 8348, 8587, and 9485 bp, respectively. The deletions were localized between the origins of replication of heavy and light strands and encompassed at least eight polypeptide-encoding genes and six tRNA genes. Sequence analysis revealed imperfect direct repeats present in all rearrangements flanking the break-points. The duplicated population accounted for 25-53% of the mitochondrial genome and was predominant to the deleted DNA (5-30%) in all cases. The proportions of the mutant population (30-75%) correlated with the age at onset of the disease. We conclude that, unlike heteroplasmic deletions, pleioplasmic rearrangements may escape selection in rapid-dividing cells, distribute widely over many tissues, and thus cause multisystem involvement. Hypoparathyroidism and deafness might be the result of altered signaling pathway caused by selective ATP deficiency.

Teratogenic effects in a case of maternal treatment for acute myelocytic leukaemia- neonatal and infantile course

Experience with the use of cytotoxic drugs in the first trimester of pregnancy is limited. We report on the clinical phenotype and infantile development of a girl born to a 36-year-old mother. Before recognition of pregnancy, the latter had been treated for acute myelocytic leukaemia receiving cytarabine, daunorubicin and doxorubicin at conception and cytarabine and thioguanine at about 35–37 days post conception. At delivery, there were severe brachycephaly, hypoplasia of the anterior cranial base and the midface as well as synostoses of both coronal and metopic sutures. Further findings included bilateral four-finger hands with hypoplastic thumbs and absent radii. This phenotype is reminiscent of the Baller-Gerold syndrome. The child, at present 15 months old, has had to undergo two operations for fronto-orbital advancement because of insufficient growth of the mid-face, nasal airway hypoplasia and increased intracranial pressure. Motor milestones are slightly retarded—neurodevelopment is otherwise normal. These findings are discussed in the context of the few previous reports and are particularly important for future genetic counselling.

Hyperphosphatasia with mental retardation

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