Novel (60%) and recurrent (40%) androgen receptor gene mutations in a series of 59 patients with a 46,XY disorder of sex development

BACKGROUND

Androgen receptor (AR) gene mutations are the most frequent cause of 46,XY disorders of sex development (DSD) and are associated with a variety of phenotypes, ranging from phenotypic women [complete androgen insensitivity syndrome (CAIS)] to milder degrees of undervirilization (partial form or PAIS) or men with only infertility (mild form or MAIS).

OBJECTIVE

The aim of the study was to characterize the contribution of the AR gene to the molecular cause of 46,XY DSD in a series of Spanish patients.

SETTING

We studied a series of 133 index patients with 46,XY DSD in whom gonads were differentiated as testes, with phenotypes including varying degrees of undervirilization, and in whom the AR gene was the first candidate for a molecular analysis.

METHODS

The AR gene was sequenced (exons 1 to 8 with intronic flanking regions) in all patients and in family members of 61% of AR-mutated gene patients.

RESULTS

AR gene mutations were found in 59 individuals (44.4% of index patients), of whom 46 (78%) were CAIS and 13 (22%) PAIS. Fifty-seven different mutations were found: 21.0% located in exon 1, 15.8% in exons 2 and 3, 57.9% in exons 4-8, and 5.3% intronic. Twenty-three mutations (40.4%) had been previously described and 34 (59.6%) were novel.

CONCLUSIONS

AR gene mutation is the most frequent cause of 46,XY DSD, with a clearly higher frequency in the complete phenotype. Mutations spread along the whole coding sequence, including exon 1. This series shows that 60% of mutations detected during the period 2002-2009 were novel.

[Hypohidrotic ectodermal dysplasia: A cause of fever of unknown origin]

The term ectodermal dysplasias includes many disorders that share some clinical features such as involvement of one or several ectodermal structures and congenital origin. Currently, 154 different types divided into 11 clinical subgroups (Freire Maia classification 1994) have been described. The most frequent entity is hypo- or anhidrotic ectodermal dysplasia (Christ-Siemens-Touraine syndrome). This is a rare hereditary disease whose main characteristic is the absence, or more often the reduction, of sweat glands, leading to an increase in body temperature together with anomalies of the epidermis and its appendages (hair and nails). We present a case of hypohidrotic ectodermal dysplasia in a premature 18-month-old boy who was referred to our department because of markedly dry skin since birth and recurrent eczematous and lichenification lesions that had been successfully treated with topical corticosteroids. Physical examination revealed mild alopecia with sparse and fine blonde hair and the absence of dental alveoli. The boy's mother had noticed slight sweating and episodes of fever without clinical symptoms, which were more frequent in summer. Hypohidrotic ectodermal dysplasia should be included in the differential diagnosis of fever of unknown origin.

[Permanent neonatal diabetes associated with other anomalies]

Neonatal diabetes mellitus is defined as hyperglycemia detected in the first month of life of more than 2 weeks' duration, requiring insulin treatment. It is extremely uncommon (1/500,000 neonates) and is permanent in only 30% of cases. Several hypotheses concerning its etiology have been postulated, such as pancreatic immaturity, paternal uniparental isidisomy of chromosome 6, and the existence of a gene located in the 6 q 22-23 chromosome region subjected to imprinting and exclusively of paternal expression. The management of these patients is usually difficult. These neonates are underweight for their gestational age, and neither anti-insulin antibodies nor anti-islets are detected. We studied a neonate hospitalized because of low weight for his gestational age with dimorphic features and hyperglycemia since the 17 th day of life. Clinical and anatomical follow-up has been periodically performed to the present date. The child presents permanent neonatal diabetes with negative antibodies. Although various insulin patterns have been used since the onset of the syndrome, management remains difficult. The child presents hypothyroidism, bilateral neurosensory deafness, bilateral congenital cataract, myopia, dimorphic features, congenital stridor and slow weight-stature curve. The results of muscle biopsy and metabolic studies were normal. Wolfram's syndrome and mitochondrial diabetes were ruled out. This is an exceptional case of permanent neonatal diabetes associated with other malformations corresponding to no known syndromic patterns.