49,XXxxy syndrome

What is 49,XXxxy syndrome?

This rare disease is a chromosomal condition that affects only males.

It is sometimes referred to as a variant of Klinefelter syndrome, but it affects individuals much more severely and varies in many ways in terms of the possible symptoms.

The main features of this syndrome include intellectual disability, infertility, birth defects and unique facial features.

What gene change causes 49,XXxxy syndrome?

The condition is caused by the presence of 3 extra x chromosomes in affected males. It is not inherited.

It is believed to be the result of mosaicism.

Mosaicism occurs when an individual has cells in their body with more or less chromosomes than the usual 46. This can trigger issues that affect different systems and parts of the body.

what are the main symptoms of 49,XXxxy syndrome?

Symptoms may vary considerably between individuals with the syndrome.

Some of the main symptoms include intellectual disability and developmental delay.
Delayed growth is common and may present as early as in the uterus.

Birth defects are also common and may affect the heart, brain, bones and kidneys.

Unique facial characteristics of the syndrome include a short stature, short neck, folder ears, a protruding lower jaw, a large and flat nose with a turned up tip, and wide-set eyes.

Infertility is also a main symptom of the syndrome.

How does someone get tested for 49,XXxxy syndrome?

The initial testing for 49,XXxxy syndrome can begin with facial analysis screening, through the FDNA Telehealth telegenetics platform, which can identify the key markers of the syndrome and outline the need for further testing. A consultation with a genetic counselor and then a geneticist will follow. 

Based on this clinical consultation with a geneticist, the different options for genetic testing will be shared and consent will be sought for further testing.   

Medical information on 49,XXxxy syndrome

Follow up of a male patient treated with testosterone was made by Mazzilli et. al. (2016). Clinical characteristics included recurrent intellectual disability, lack of social interaction, respiratory infections, hypertelorism, divergent strabismus, cervicodorsal kyphosis, both bilateral planus feet and hallux valgus. Specific andrologic examination revealed testicular hypoplasia, non-palpable epididymis, micropenis, hypergonadotrophic hypogonadism, and vitamin D deficiency. Testosterone and cholecalciferol replacement resulted in an increase in pubic hair growth, testicular volume and size of the penis, as well as reduction of BMI, normalisation of vitamin D values, and improving of social interaction, posture, gait and postural autonomy in walking.
A male patient with 49, XXXXY was reported by Şahin et. al. (2017). Clinical characteristics included prenatal diagnosis of growth retardation, abnormal posture in lower extremities, and extensive edema. Later, intellectual disability, eunuchoid body structure with truncal obesity, slender fingers of both hands, big toes on both feet, inward patella, narrow nail beds, hypergonadotrophic hypogonadism and micropenis were noted. Dysmorphic features were broad forehead, slightly down-slanted palpebral fissures, large and prominent nasal root, small posteriorly rotated ears and micrognathia. Her older sister has 45,X0 (Turner) syndrome. Karyotype of both parents was normal.
Putra et. al. (2018) described a fetus with pentasomy 49, XXXXY diagnosed by microarray and fetal karyotype. Prenatal findings were bilateral clubfeet, clinodactyly of the left fifth digit, micropenis, echogenic bowel, and fetal growth restriction. Pregnancy was terminated at 36th week.

* This information is courtesy of the L M D.

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