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1p36 Chromosome Deletion

written by: KM•edited by: Paul Arnold•updated: 2/28/2010

A look at one of the most familiar case of chromosome aberration - 1p36 chromosome deletion - its signs and symptoms and some of its major clinical findings.

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    Monosomy 1p36 or the deletion of the chromosome band 1p36 (on the outermost band on the short arm of chromosome 1), has been recognized as one of the most common case of chromosome deletion with incidence of 1 in 5,000 to 1 in 10,000. This monosomy can exist in association with other chromosomal imbalances or it can be found in its “pure” state. The condition was not discovered and ascertained earlier because of the difficulty to detect the deletion with the conventional chromosomal analyses. Since it was diagnosed in 1980s using the amniocentesis, high-resolution G-banding, chromosome-specific fluorescence in-situ hybridization (FISH) with probes for 1p and by subtelomeric probe screening, knowledge on this chromosomal aberration have greatly increased and clear clinical descriptions were consequently laid.

    Major Clinical Findings for Monosomy 1p36

    Mental Retardation and Central Nervous System Aberrations

    Almost 75% of those diagnosed with monosomy 1p36 were observed to have distinctive facial features, characterized with the condition’s hallmark such as mental retardation, poor or absent of speech, hypotonia, brachycamptodactyly, short feet, and some brain abnormalities. Central nervous system defects account for as high as 88% of those with 1p36 chromosomal deletion where there is the dilatation of the lateral ventricles of the brain that can go as deep as the subarachnoid spaces; diffuse brain and cortical atrophies are also common. Affected children aging two to seven years old are able to walk alone with a broad-based gait. The absence of expressive language is also a characteristic of those with this condition and that “language” is often limited to the level of first word associations only.

    Structural Heart Defects and Seizures

    It was also found out from recent studies that 50%-75% of those with 1p36 deletion are more prone to congenital heart diseases and observed to possess structural heart defects such as ventricular and atrial abnormalities and heart valvular defects to name a few. Moreover, the same percentage of children with this chromosomal deletion suffer from opthalmologic abnormalities such as refractive errors, strabismus and visual inattention. Another common characteristic of individuals with this chromosomal disorder are seizures. Onset ages are as early as four days to two years. Seizures can come in several forms such as the generalized types like tonic to tonic-clonic or to the partial types (simple or complex) seizures.

    Bones and Genitourinary Malformations

    A lesser bulk with monosomy 1p36 (25%-50%) have skeletal anomalies such as scoliosis, asymmetrical lower limbs and can go as delicate as delayed bone age further exposing the bones to fractures and other damages. The same portion of patients have genitourinary malformations which cane be readily observed with unilateral renal pelvis as well as unilateral pelvic ecstasia. For males, micropenises are often characterized while smaller labia minora and clitoris are the malformations observed in females. In behavioral context, children with 1p36 deletions have poor social mechanisms commonly observed as temper tantrums, biting of hands and even the wrists.

    What can be done?

    After initial diagnosis of the condition, thorough evaluation should follow in order to manage the signs and symptoms of the condition. Evaluation includes the measurement of several growth parameters, evaluation of the language, cognitive, motor and social skills development. Rehabilitation programs are also available to those mentally retarded patients that most often offer therapies for malfunctioned motor skills such as walking and self-feeding. Lastly, standard pharmacotherapy are also readily available for children with heart defects as well as to those with opthalmologic anomalies.

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