A Comparative Phenotypic Study of Kallmann Syndrome Patients Carrying Monoallelic and Biallelic Mutations in the Prokineticin 2 or Prokineticin Receptor 2 Genes

Context: Both biallelic and monoallelic mutations in PROK2 or PROKR2 have been found in Kallmann syndrome (KS). Objective: The objective of the study was to compare the phenotypes of KS patients harboring monoallelic and biallelic mutations in these genes. Design and Patients: We studied clinical and endocrine features that reflect the functioning of the pituitary-gonadal axis, and the nonreproductive phenotype, in 55 adult KS patients (42 men and 13 women), of whom 41 had monoallelic mutations and 14 biallelic mutations in PROK2 or PROKR2. Results: Biallelic mutations were associated with more frequent cryptorchidism (70% vs. 34%, P < 0.05) and microphallus (90% vs. 28%, P < 0.001) and lower mean testicular volume (1.2 ± 0.4 vs. 4.5 ± 6.0 ml; P < 0.01) in male patients. Likewise, the testosterone level as well as the basal FSH level and peak LH level under GnRH-stimulation were lower in males with biallelic mutations (0.2 ± 0.1 vs. 0.7 ± 0.8 ng/ml; P = 0.05, 0.3 ± 0.1 vs. 1.8 ± 3.0 IU/liter; P < 0.05, an...