Kallmann Syndrome associated with a large deletion of KAL1 gene

Introduction: The Kallmann Syndrome is a clinically and genetically heterogeneous disease, frequently characterized by an association between hypogonadotropic hypogonodism and anosmia or hyposmia. The X-linked form of this syndrome is caused by mutations affecting the KAL1 gene that encodes the extracellular glycoprotein anosmin-1 responsible for the migration of GnRH neurons and olfactory nerves to the hypothalamus. Methods: Molecular diagnosis was performed in a patient with a phenotype of micropenis and strabismus, diagnosed as Kallmann Syndrome. Molecular analysis was performed by PCR and DNA sequencing of the amplified KAL1 exons. Absence of amplification of specific exons was validated by MLPA(Multiplex Ligation-dependent Probe Amplification) in order to confirm a gross gene deletion. Results: The propositus and his mother are carriers of a deletion that comprises exons 4 to 14 detected by PCR and MLPA. Discussion/Conclusion: The patient has a normal male karyotype. Molecular analysis allowed the identification of a large deletion covering exons 4 to 14 of the KAL1 gene. In turn, is mother is heterozygous for this deletion, allowing us to conclude that the patient’s KAL1 gene deletion was inherited, and as expected, is of maternal origin. The patient has a gross deletion of KAL1 that, up to date, is not reported in the scientific literature. Several other KAL1 whole or partial gene deletions have been identified as the cause of this syndrome. In this specific case, the absence of almost the whole KAL1 gene is the molecular basis of the patient phenotype. The identified molecular defect, allowed a better genetic counselling to the nuclear family as well as to other family members