Reifenstein syndrome is a type of androgen insufficiency. Reifenstein syndrome occurs in men when their body is unable to appropriately respond to androgens and testosterone. It is characterized by ambiguous external genitalia, gynecomastia, and infertility due to sclerosis of the seminal tubules.
Males with Reifenstein syndrome have partial androgen insensitivity; they are born with external male sex features. Affected men often present for clinical workup at the time of puberty, with the following physical characteristics and/or complaints  :
It is important to note a contrast of presenting symptoms between men with Reifenstein syndrome (partial androgen insensitivity) to those with complete androgen insensitivity. Men with complete androgen insensitivity often present with external female sex characteristics (without a uterus), internal male sex characteristics (e.g., undescended testes), and absent or very little pubic or axillary hair.
Diagnosis of Reifenstein syndrome consists of a history, physical findings, blood tests, genetic tests, sperm count, and less often a testicular biopsy. Physical findings include varying degrees of ambiguous external genitalia, small penis and scrotum, undescended testes, space facial hair, and gynecomastia. Affected individuals may also have partially developed female sex organs, a small or missing vas deferens.
Blood tests for various sex hormones (testosterone and its derivatives, anti-müllerian hormone, sex hormone-binding globulin, luteinizing hormone) are often performed. Prior to puberty, laboratory tests will reflect normal levels of testosterone, dihydrotestosterone, and luteinizing hormone. Following puberty, there may be normal or elevated testosterone with elevated levels of luteinizing hormone. Additionally, either during the first year of life or the following puberty, men will often have elevated levels of anti-müllerian hormone .
An abdomen/pelvic ultrasound is the most useful radiological test. Findings commonly demonstrate the absence of a uterus, impaired development of prostate and Wolffian duct derivatives, and undescended testes   . In rare instances where there is a palpable mass or otherwise clinically indicated, a magnetic resonance imaging may be used to visualize the pelvic anatomy.
Genetic analysis will show a normal 46 XY chromosomal pattern. Genetic defects in the androgen receptor (AR) gene cause androgen insensitivity syndrome by preventing the androgen receptors from functioning correctly. A mutation of the AR gene causes cells to be less responsive or refractory to androgens. Androgens and androgen receptors also play a role in hair growth and libido. Depending on the degree of mutation of the AR gene, an affected individual's sex characteristics can vary from mostly female to mostly male    . A DNA analysis of the androgen receptor gene will detect any mutations in the AR gene. The number of CAG repeats in exon 1 of the AR gene have been shown to be inversely proportional to the transcriptional activity of the androgen target gene; in other words, the greater the number of trinucleotide CAG repeats, the greater the degree of androgen insensitivity.