Molecular cytogenetic characterization of a mosaic small supernumerary marker chromosome derived from chromosome Y in an azoospermic male: A case report

RATIONALE: Small supernumerary marker chromosomes (sSMCs) can be usually discovered in the patients with mental retardation, infertile couples, and prenatal fetus. We aim to characterize the sSMC and explore the correlation between with sSMC and male infertility. PATIENT CONCERNS: A 26-year-old Chinese male was referred for infertility consultation in our center after 1 year of regular unprotected coitus and no pregnancy. DIAGNOSIS: Cytogenetic G-banding analysis initially described a mosaic karyotype 47,X,Yqh-,+mar[28]/46,X,Yqh-[22] for the proband, while his father showed a normal karyotype. The chromosome microarray (CMA) analysis showed there existed a duplication of Yp11.32q11.221, a deletion of Yq11.222q12, a duplication of 20p11.1 for the patient. Azoospermia factor (AZF) microdeletion analysis for the patient showed that he presented a de novo AZFb+c deletion. Fluorescence in situ hybridization further confirmed the sSMC was an sSMC(Y) with SRY signal, Y centromere, and Yq deletion. INTERVENTIONS: The patient would choose artificial reproductive technology to get his offspring according to the genetic counseling. OUTCOMES: The sSMC in our patient was proved to be an sSMC(Y), derived from Yq deletion. The spermatogenesis failure of the proband might be due to the synthetic action of sSMC(Y) mosaicism and AZFb+c microdeletion. LESSONS: It is nearly impossible to detect the chromosomal origin of sSMC through traditional banding techniques. The molecular cytogenetic characterization could be performed for identification of sSMC so that comprehensive genetic counseling would be offered.