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NORD gratefully acknowledges Gioconda Alyea, MD (FMG), MS, National Organization for Rare Disorders, for assistance in the preparation of this report.
Summary
Congenital megaprepuce (CMP) is a rare type of buried penis, a condition where a normal sized penis is hidden by excessive foreskin. Foreskin (prepuce) is a fold of skin the covers the top of the penis. CMP is characterized by a tight preputial ring (opening of the foreskin) and extreme ballooning of the inner foreskin due to urine buildup. This happens because the narrow opening traps urine, creating pressure that causes the inner foreskin to swell into a formation described as a “preputial bladder.”
The exact cause remains unclear, but research suggests it may come from a combination of genetic factors, having underdeveloped penile shaft skin and severe phimosis (a condition where the foreskin cannot be pulled back). In some people, CMP appears with other abnormalities like hypospadias (where the urethra opens on the underside of the penis) or penile curvature, though more research is needed to understand these connections.
CMP is typically diagnosed in infancy, often after parents notice that their baby boy has difficulty with urination or an unusual appearance to the penis. Most infants have only minor urinary issues, but untreated CMP can cause psychological distress in older children and adolescents due to appearance and potential difficulties with sexual function. CMP isn’t present at birth, but it becomes noticeable a few months later as severe phimosis (a tight foreskin) causes urine to collect, leading to the ballooning and other symptoms.² The condition seems to progress after birth, likely because of worsening phimosis, which increases the urine buildup and foreskin stretching.
Surgery is the recommended treatment, ideally performed soon after diagnosis.
Introduction
Congenital megaprepuce is a subtype of buried penis. Buried penis refers to a penis of normal size hidden by preputial skin (foreskin). Various terms such as buried penis, trapped penis, webbed, concealed, or entrapped were all seemingly used in the past to describe the same condition. Causes of buried penis include trapped penis associated with scarring after circumcision, concealed penis because of excessive suprapubic fat, and megaprepuce and webbed penis happening because of abnormal penoscrotal fusion. 1,2 CMP was first described in 1994.
Children with congenital megaprepuce (CMP) usually show signs and symptoms within the first few months of life. Common symptoms include:
Doctors may notice the characteristic swelling, especially after the child urinates. The swelling usually disappears after the trapped urine is pressed out. The penis and glans (head of the penis) are typically normal in size, though they may feel hidden under the surrounding tissue. The penoscrotal angle (where the scrotum meets the base of the penis) may appear abnormal, and in some boys, part of the scrotum seems to extend higher onto the penis (penoscrotal transposition). 1.2
CMP is usually isolated (not associated with other birth defects) but some studies have reported a link to hypospadias and chordee (a downward curve of the penis).
The exact cause of congenital megaprepuce (CMP) is not fully understood but it’s thought to happen because of abnormal development during the formation of the external male genitalia. The cause is likely multifactorial, involving a combination of genetics, tissue development issues and phimosis.3,4,5
Normally, during early pregnancy (around 6 weeks), the scrotal tissue moves from the groin to its final position below the penis and the penile shaft and foreskin form from tissue that stretches and fuses around the urethra. 1,2 In CMP, that process doesn’t happen correctly. The tissue that is supposed to separate and form the penis and scrotum stay stick together. This leads to a high-riding scrotum (higher than normal position of the testes) and tethering of the penile tissue. This causes a shortage of ventral (underside) penile skin, abnormal dartos fascia (a layer of connective tissue that helps hold everything in place) and improper anchoring of the skin at the base of the penis.1.2
Congenital megaprepuce (CMP) is rare and its true prevalence is unknown. As of 2011, only 868 cases had been reported in the medical literature. However, these cases were described using different criteria, which makes it hard to know how common the condition really is.⁵
A study published in 2012 detailed a 12-year experience with 52 cases of CMP, covering the period from 1999 to 2011. A 2020 study discussed the early surgical repair of congenital completely buried penis in children, reporting on 103 cases. 6,7 However, it did not specify how many of these were specifically CMP.
Congenital megaprepuce (CMP) is usually diagnosed based on physical examination and the child’s symptoms. Doctors look for key signs like severe ballooning (swelling) of the inner foreskin, poor urinary stream, and the need for someone to manually remove the urine (manual urine expression). The penis is normal but hidden beneath the excessive, swollen foreskin.1
The timing of diagnosis can vary. While the malformation is there from birth, it may not become obvious until a few months later when urine starts collecting inside the foreskin because of the narrow opening.1,4,5
Treatment
Surgical correction is considered necessary to relieve symptoms, improve appearance and prevent long-term issues like urinary infections or emotional distress.
Circumcision is not recommended because the extra foreskin is needed to reconstruct the penile shaft.¹ The goals of surgery are to improve both function and appearance. Parents often choose surgery because of concerns about the appearance of the hidden penis and the child’s difficulty urinating.
Common reasons for surgery include:2
There are several surgical techniques used by the surgeons to fix this problem. While each method follows similar principles, the main difference is how the surgeon covers the penile shaft after fixing the problem.
Surgical approaches can be broadly categorized into: 2,5
The goal of all surgical methods is to create a functional, cosmetically acceptable penis, ensure the child can urinate normally without swelling or manual expression and prevent long-term complications like infections or psychological distress.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222
TTY: (866) 411-1010
Email: [email protected]
Some current clinical trials also are posted on the following page on the NORD website:
https://rarediseases.org/living-with-a-rare-disease/find-clinical-trials/
For information about clinical trials sponsored by private sources, contact: www.centerwatch.com
For information about clinical trials conducted in Europe, contact: https://www.clinicaltrialsregister.eu/
NORD strives to open new assistance programs as funding allows. If we don’t have a program for you now, please continue to check back with us.
NORD and MedicAlert Foundation have teamed up on a new program to provide protection to rare disease patients in emergency situations.
Learn more https://rarediseases.org/patient-assistance-programs/medicalert-assistance-program/Ensuring that patients and caregivers are armed with the tools they need to live their best lives while managing their rare condition is a vital part of NORD’s mission.
Learn more https://rarediseases.org/patient-assistance-programs/rare-disease-educational-support/This first-of-its-kind assistance program is designed for caregivers of a child or adult diagnosed with a rare disorder.
Learn more https://rarediseases.org/patient-assistance-programs/caregiver-respite/No patient organizations found related to this disease state.