[Children with idiopathic hypogonadotropic hypogonadism: clinical data analysis and mutations analysis of KAL1 and FGFR1 gene].

Objective: To summarize the clinical features of idiopathic hypogonadotropic hypogonadism (IHH) diagnosed during childhood, and detect mutations in KAL1 and FGFR1, acting as key clues for diagnoses.

Method: We collected and analyzed clinical data of 21 cases (including demographic data, chief complaint, history of present illness, family history, physical examination, laboratory tests and imaging studies, etc.) diagnosed with IHH from December 2008 to February 2013. Polymerase chain reaction and gene sequencing was applied to detect mutations on KAL1 and FGFR1. Fifty healthy unrelated individuals were choosen as controls.

Result: Of 21 patients with IHH, 19 were males and 2 females, they visited us initially from 8-17 years old, with an average of (13.58 ± 2.38) years old. Sixteen cases were KS patients (76%). One boy reported abnormal sense of smelling but having olfactory perfect picture on MRI; 2/19 male cases had no puberty when they were over 13-14 years old without abnormal external genitalia. 8/19 cases only had small penis, 8/19 had both of cryptorchidism and small penis, and the Case 2 also had hypospadias. One boy had cryptorchidism combined with a normal penis. Only 2 girls diagnosed as IHH who visited us because of no puberty signs when they were 13 and 16 years old, respectively. Other clinical manifestations included: one with gynecomastia, 2 had mental retardation, and one was deaf; one with high palatal arch; one with mirror-movement and one with left renal agenesis but normal renal function respectively. Laboratory tests showed that the basic testosterone (T) is low and with inappropriately low or normal gonadotropin hormones. The results of cases of standard human chorionic gonadotropin (HCG) test of 7 cases out of 19 male children's were normal (testosterone>1 100 ng/L), and another nine cases continued to complete the extended HCG test, and the testosterone levels of two of them (cases 6, 8) were still lower than 1 000 ng/L. Family history: the parents in 9/21 family had delayed puberty, involving only one parent in 6 families, involving both in 2 families and the other one was an uncle having micropenis with a child. Among these 21 cases, only one boy's father had hyposmia and his first emission age was 14-15 years. Eleven patients accompanied abnormal sense of smelling and the olfactory organ abnormalities on MRI, 4 had olfactory organ abnormalities on MRI while they had good smelling function self-reportedly. We got 15 samples (12 KS and 3 nIHH cases) to screen the mutation of KAL1 (14 exons) and FGFR1 (18 exons). A splicing mutation c.1062+1G>A in KAL1 is identified in case 17 with IHH. One novel heterozygous FGFR1 mutation, a single base deletion mutation on the exon 1 c.27delC is identified in case 14. This mutation causes the premature termination codons.

Conclusion: This pilot research showed that IHH/KS diagnosis in children depends on clinical manifestation rather than gene analysis. Small penis or cryptorchidism, smelling abnormality and positive familial history may contribute to the KS/HH diagnosis. MRI of olfactory bulb acts as important proof for diagnosis of KS. Mutations in KAL1 and FGFR1 gene are not main causes of Kallmann syndrome.