What is the role of genetics in the etiology of microphallus?

Updated: Nov 30, 2020
  • Author: Karen S Vogt, MD; Chief Editor: Sasigarn A Bowden, MD  more...
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Features of this syndrome include hypergonadotropic hypogonadism, tall stature, gynecomastia, small firm testes, increased leg length in proportion to height, and increased risk for learning difficulties. [27]

Prader-Willi syndrome (PWS)

Hypogonadism is a feature of PWS and usually manifests in males as cryptorchidism and an underdeveloped scrotum. Some also have a micropenis. Characteristic features of PWS include hypotonia, weak suck, feeding difficulties and failure to thrive in infancy with later development of hypothalamic hyperphagia and often obesity. Motor and language developmental delay, short stature, small hands and feet, emotional instability (perseveration, obsessions and compulsions), almond-shaped eyes, and triangular mouth are additional features. PWS occurs in 1:20,000 live births. The underlying genetic abnormality is the lack of expression of genes on the Prader-Willi critical region, 15q11.2-13, of the paternally inherited chromosome 15, which may be due to deletion (70%), maternal uniparental disomy (25%), or a imprinting defect (5%). [28]

Bardet-Biedl syndrome

Features of this syndrome include hypogonadotropic hypogonadism, rod-cone dystrophy with progressive visual impairment, obesity, short stature, polydactyly, developmental delay, renal anomalies leading to end-stage renal disease, and hepatic fibrosis. Inheritance of this syndrome is in an autosomal recessive pattern and mutations in 14 genes have been implicated. [29]

Noonan syndrome

Features of this syndrome include short stature, webbed neck, hypertelorism, ptosis, low posterior hairline, low-set ears, pectus excavatum, cryptorchidism, valvular pulmonary stenosis, lymphedema, and bleeding abnormalities. Noonan syndrome is inherited in an autosomal dominant manner, although approximately half of all cases represent new mutations. Mutations in the PTPN11 gene are found in 50% and smaller percentages have mutations in KRAS, SOS1, and RAF1. [30]

CHARGE syndrome

The syndrome is defined by coloboma, heart disease, atresia choanae, retarded growth and development, genital anomalies and hypogonadism, and ear anomalies and deafness. Neuropathic bladder, hydronephrosis, vesicoureteral reflux, and ureteropelvic junction obstruction may also occur. Given these potential renal and urinary tract abnormalities, bladder and renal ultrasonography and voiding cystourethrography (VCUG) are indicated in those suspected of having this syndrome. Sixty to seventy percent have a mutation in the CHD7 gene. [31, 32]


More rare genetic syndromes associated with micropenis include Robinow syndrome, Rud syndrome, and IMAGe syndrome. [14]

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