Morris Syndrome: Causes, Symptoms and Cure

June 27, 2024

In today’s article, we discuss Morris syndrome, a condition in which the body does not respond to male hormones.

We’ll understand what it is, its causes, symptoms, how a diagnosis is made, if there are treatments and what they are, and if prevention is possible.

What is Morris Syndrome?

Morris Syndrome, also known as androgen insensitivity syndrome or testicular feminization, is a rare genetic condition that affects sexual development.

This syndrome occurs in genetically male individuals (with XY chromosomes), but whose body does not respond, or responds only partially, to male sex hormones called androgens, particularly testosterone.

This insensitivity to androgens can be complete or partial, giving rise to two main variants of the syndrome.

In the complete form, the individual develops typically female external physical characteristics, despite having a male chromosomal makeup. It is a condition different from that defined as intersex.

In the partial form, the appearance can vary from predominantly female to predominantly male, with various intermediate gradations.

It’s important to understand that Morris Syndrome is not a choice, but a congenital condition that develops during intrauterine life.

This biological peculiarity leads to a series of medical, psychological, and social challenges for affected individuals and their families.

morris syndrome

What are the causes?

The main cause of Morris Syndrome lies in a genetic mutation.

Specifically, the responsible gene is called AR (Androgen Receptor), located on the X chromosome.

This gene has the task of producing a protein that acts as a receptor for androgens, allowing these hormones to interact with body cells and perform their functions.

When the AR gene is mutated, the androgen receptor may be absent or present in reduced quantities, or it may not function correctly.

Consequently, even if the body normally produces testosterone, the cells are unable to respond adequately to this hormone.

The mutation can occur spontaneously during embryonic development or can be inherited from the mother.

In fact, about two-thirds of cases are due to hereditary transmission, while the remaining third is the result of spontaneous mutations.

It’s interesting to note that, being an X-linked condition, it’s generally genetically male individuals (XY) who manifest the syndrome.

Women with a mutated X chromosome are usually healthy carriers, as the second X chromosome compensates for the mutation.

How is the diagnosis made?

The diagnosis of Morris Syndrome can occur at different times in life, depending on the form and severity of the condition.

In the complete form, the diagnosis is often made during adolescence, when an apparently normal girl does not start menstruating.

In some cases, the diagnosis can be made earlier, for example during childhood, if an inguinal hernia occurs.

During surgery to repair the hernia, doctors may discover the presence of undescended testicles, which leads to further investigations.

To confirm the diagnosis, doctors may resort to various procedures:

  • Blood tests to measure testosterone levels, which are normal or elevated despite the female appearance.
  • Abdominal ultrasound to verify the absence of uterus and ovaries.
  • Genetic tests to confirm the presence of XY chromosomes and the AR gene mutation.
  • In some cases, a biopsy of gonadal tissues may be necessary.

It is also possible, although rare, to make a prenatal diagnosis through techniques such as chorionic villus sampling or amniocentesis, especially if there is a family history of Morris Syndrome.

What are the symptoms?

The symptoms of Morris Syndrome vary considerably depending on whether it’s the complete or partial form.

In the complete form, the individual appears externally as a typical female.

Symptoms may include:

  • Female external genitalia
  • Breast development during puberty
  • Absence of menstruation
  • Shorter than normal vagina
  • Absence of pubic and axillary hair or their very reduced presence
  • Absence of acne during adolescence
  • Slightly above average female height

In the partial form, symptoms can be very variable, ranging from a predominantly female appearance to a predominantly male one. They may include:

  • Ambiguous or partially masculinized genitals
  • Possible presence of both male and female structures
  • Variable breast development
  • Reduced body hair growth

In both forms, the presence of undescended testicles (cryptorchidism) and the absence of uterus, ovaries, and fallopian tubes are common.

What are the treatments?

There is no definitive cure for Morris Syndrome, as it’s not possible to correct the genetic mutation at the root of the condition.

However, several treatments are available to manage symptoms and improve patients’ quality of life.

Treatment depends on the form of the syndrome and individual patient preferences. It may include:

  • Hormone therapy: after puberty, especially if the testicles are removed, estrogen replacement therapy is necessary to maintain female secondary sexual characteristics and prevent osteoporosis.
  • Surgical interventions: removal of undescended testicles (gonadectomy) may be necessary to prevent the risk of tumors. In some cases, genital reconstruction surgeries may be opted for.
  • Psychological support: it’s fundamental to help the patient and family face the emotional and social challenges related to the condition.
  • Vaginal dilation: in complete forms, it may be necessary to lengthen the vagina to allow satisfying sexual intercourse.
  • Fertility management: since patients are sterile, options such as adoption or surrogacy can be discussed.

It’s important to emphasize that treatment must be personalized and thoroughly discussed with a multidisciplinary team of specialists, carefully considering the patient’s wishes and expectations.

Is it possible to prevent it?

Unfortunately, there are no known methods to prevent Morris Syndrome.

Being a genetic condition, it is not influenced by environmental or behavioral factors.

However, for families with a history of Morris Syndrome, genetic counseling is possible.

This can help understand transmission risks and available options in case of pregnancy.

In some cases, couples at risk might consider assisted reproduction techniques with embryo selection to avoid transmitting the mutation.

However, these are complex decisions that require careful ethical and personal evaluation.

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Singh S, Ilyayeva S. Androgen Insensitivity Syndrome. [Aggiornato 2023 Feb 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Gen-. Disponibile qui:

About the Author

Severino Cirillo

Health, Wellness and Education Expert. With a degree in Community Health, he is the CEO of Informed Parent and is responsible for validating the blog's scientific information and coordinating the editorial team of experts, consisting of gynecologists, midwives, psychotherapists, and others in pregnancy, perinatal, and parenting wellness and health.