CASE REPORTS

Two brothers, aged 36 and 35 years respectively, were examined in 1998 and 2000. The first had azoospermia, shown by repeated semen analyses, while the second had oligozoospermia (sperm count 200 000/ml, with reduced motility and abnormal morphology in 96% of sperm). In both patients, hormone values, ultrasound analysis, and karyotype were normal. Screening for microdeletions was performed in the two brothers and in their 69 year old father using PCR amplification of 20 loci on the Y chromosome (table 1). FISH analysis was performed on fixed metaphase chromosomes from the two sons and the father with specific probes for the DAZ and VCY2 genes.

In both patients, PCR analysis disclosed an identical deletion encompassing loci sY152 to sY158 (AZFc), with loss of the DAZ, VCY2, and CDY1 genes (fig 1, table 1). The Y chromosome was then tested in their father and the same AZFc deletion was detected. Paternity was confirmed using a panel of STR markers. PCR results were confirmed by FISH with probes for DAZ and VCY2,⁷ which showed loss of both genes in the father and in his sons in 30 metaphases each, while in healthy controls at least 90% of metaphases showed positive signals on the Y chromosome (fig 2). This deletion falls within the region recently identified by Kuroda-Kawaguchi et al⁸ as involved in the majority of AZFc deletions. Thus, the size of the deletion can be estimated to be 3.5 Mb.

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Figure 1

Duplex PCR reaction using primers for the SRY gene and for STSs sY152 (lanes 1-4) and sY254 (lanes 5-8). Lanes 1 and 5 = normal male control; lanes 2 and 6 = first son; lanes 3 and 7 = second son; lanes 4 and 8 = father.

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Figure 2

FISH analysis with SRY (pink) and DAZ (yellow) specific probes. (A) Normal control male showing signals of both probes on the Y chromosome. (B) First son showing only SRY signal on the Y chromosome, owing to AZFc deletion with loss of the DAZ gene.

DISCUSSION

Like the other two reported cases, in our family the father and sons had an identical deletion involving AZFc with loss of the genes DAZ, VCY2, and CDY1, but showed different phenotypes.^5,6 This confirms that AZFc microdeletions can be associated with features ranging from normal fertility, to mild oligozoospermia,⁹ to infertility, characterised by severe oligozoospermia or azoospermia. These differences are not age related, since the father was fertile until the age of 34 years, while the sons were already infertile at that age. Other genetic or environmental factors affecting the phenotype of patients with AZFc deletions must be present. Since one in six couples requires assisted reproduction for a pregnancy, knowledge of the phenotype resulting from the transmission of a Yq microdeletion is crucial. While these factors remain unknown, care should be taken in the counselling of patients with AZFc deletions undergoing ICSI, since data from these families suggest that the son will not invariably inherit the same pattern of spermatogenesis. Further studies on families with multiple carriers of the same deletion, but showing different phenotypes will be of help for the identification of these factors.