Brain-lung-thyroid syndrome

Also known as: BLT syndrome; brain-thyroid-lung syndrome; CAHTP; choreoathetosis, hypothyroidism, and neonatal respiratory distress; chreoathetosis and congenital hypothyroidism with or without pulmonary dysfunction

Definition

Genetics Home Reference

Brain-lung-thyroid syndrome is a group of conditions that affect the brain, lungs, and thyroid gland (a butterfly-shaped gland in the lower neck). Brain-lung-thyroid syndrome historically included problems with all three organs, although the designation now encompasses a combination of brain, lung, and thyroid problems. About 50 percent of affected individuals have problems with all three organs, about 30 percent have brain and thyroid problems, and about 10 percent have brain and lung problems. The brain alone is affected in 10 to 20 percent of people with the condition. Such cases are sometimes called isolated benign hereditary chorea.

Nearly everyone with brain-lung-thyroid syndrome has brain-related movement abnormalities. Benign hereditary chorea is the most common feature of the syndrome. This feature is associated with involuntary jerking movements (chorea) of the face, torso, and limbs; writhing movements (athetosis) of the limbs; and other movement problems. Individuals with brain-lung-thyroid syndrome can have other abnormalities, such as difficulty coordinating movements (ataxia), muscle twitches (myoclonus), and involuntary muscle contractions that result in twisting and repetitive movements (dystonia). The movement problems typically begin around age 1, although they can begin in early infancy or later in life, and are often preceded by weak muscle tone (hypotonia). They can delay the development of walking. The movement problems usually remain stable and can improve over time. Some affected individuals also have learning difficulties or intellectual disability.

Thyroid problems are the next most common feature of brain-lung-thyroid syndrome. The thyroid gland makes hormones that help regulate a wide variety of critical body functions, including growth, brain development, and the rate of chemical reactions in the body (metabolism). Many affected individuals have reduced thyroid function from birth (congenital hypothyroidism), resulting in lower-than-normal levels of thyroid hormones. Others have a milder condition called compensated or subclinical hypothyroidism, in which thyroid hormone levels are within the normal range, even though the thyroid is not functioning properly. While most people with brain-lung-thyroid syndrome have a normal-sized thyroid, the gland is reduced in size (hypoplastic) or absent (aplastic) in some affected individuals. Although a shortage of thyroid hormones can cause intellectual disability and other neurological problems, it is unclear whether such issues in individuals with brain-lung-thyroid syndrome are due to hypothyroidism or to the brain abnormalities related to the condition.

Lung problems are common in brain-lung-thyroid syndrome. Some affected newborns have respiratory distress syndrome, which causes extreme difficulty breathing and can be life-threatening. Other affected individuals develop widespread lung damage (interstitial lung disease) or scarring in the lungs (pulmonary fibrosis), both of which can also lead to breathing problems. Recurrent lung infections, which can be life-threatening, also occur in people with brain-lung-thyroid syndrome. People with brain-lung-thyroid syndrome have a higher risk of developing lung cancer than do people in the general population.

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Orphanet

Brain-lung-thyroid syndrome is a rare disorder characterized by congenital hypothyroidism (CH), infant respiratory distress syndrome (IRDS) and benign hereditary chorea (BHC; see these terms).

Go To Source: Orphanet

Symptoms

Medical Term Other Names Description
Ataxia Cerebellar ataxia Cerebellar ataxia refers to ataxia due to dysfunction of the cerebellum. This causes a variety of elementary neurological deficits including asynergy (lack of coordination between muscles, limbs and joints), dysmetria (lack of ability to judge distances that can lead to under- oder overshoot in grasping movements), and dysdiadochokinesia (inability to perform rapid movements requiring antagonizing muscle groups to be switched on and off repeatedly).
Abnormal lung morphology Abnormality of the lungs, Abnormally shaped lung, Unusal lung shape, Abnormality of lung morphology, Lung disease [more] Any structural anomaly of the lung.
Scarring Scar tissue
Stereotypy Stereotyped behaviors, Stereotyped, repetitive behaviour, Stereotypic behavior, Repetitive or self-injurious behavior, Sterotyped behavior, Stereotypical motor behaviors, Repetitive movements [more] A stereotypy is a repetitive, simple movement that can be voluntarily suppressed. Stereotypies are typically simple back-and-forth movements such as waving of flapping the hands or arms, and they do not involve complex sequences or movement fragments. Movement is often but not always rhythmic and may involve fingers, wrists, or more proximal portions of the upper extremity. The lower extremity is not typically involved. Stereotypies are more commonly bilateral than unilateral.
Generalized hypotonia Generalized muscular hypotonia, Decreased muscle tone, Low muscle tone, Hypotonia [more] Generalized muscular hypotonia (abnormally low muscle tone).
Athetosis Involuntary writhing movements, Athetoid movements A slow, continuous, involuntary writhing movement that prevents maintenance of a stable posture. Athetosis involves continuous smooth movements that appear random and are not composed of recognizable sub-movements or movement fragments. In contrast to chorea, in athetosis, the same regions of the body are repeatedly involved. Athetosis may worsen with attempts at movement of posture, but athetosis can also occur at rest.
Dystonia Dystonic movements, Dystonic disease An abnormally increased muscular tone that causes fixed abnormal postures. There is a slow, intermittent twisting motion that leads to exaggerated turning and posture of the extremities and trunk.
Chorea Choreiform movements, Choreic movements, Choreatic disease [more] Chorea (Greek for 'dance') refers to widespread arrhythmic involuntary movements of a forcible, jerky and restless fashion. It is a random-appearing sequence of one or more discrete involuntary movements or movement fragments. Movements appear random because of variability in timing, duration or location. Each movement may have a distinct start and end. However, movements may be strung together and thus may appear to flow randomly from one muscle group to another. Chorea can involve the trunk, neck, face, tongue, and extremities.
Thyroiditis Thyroid gland inflammation Inflammation of the thyroid gland.
Muscle fibrillation Twitching Fine, rapid twitching of individual muscle fibers with little or no movement of the muscle as a whole. If a motor neuron or its axon is destroyed, the muscle fibers it innervates undergo denervation atrophy. This leads to hypersensitivity of individual muscle fibers to acetyl choline so that they may contract spontaneously. Isolated activity of individual muscle fibers is generally so fine it cannot be seen through the intact skin, although it can be recorded as a short-duration spike in the EMG.
Fasciculations Muscle fasciculation, Muscle twitch Fasciculations are observed as small, local, involuntary muscle contractions (twitching) visible under the skin. Fasciculations result from increased irritability of an axon (which in turn is often a manifestation of disease of a motor neuron). This leads to sporadic discharges of all the muscle fibers controlled by the axon in isolation from other motor units.
Involuntary movements Involuntary muscle contractions Involuntary contractions of muscle leading to involuntary movements of extremities, neck, trunk, or face.
Interstitial pulmonary abnormality Interstitial lung disease Abnormality of the lung parenchyma extending to the pulmonary interstitium and leading to diffuse pulmonary fibrosis.
Hypothyroidism Low T4, Underactive thyroid Deficiency of thyroid hormone.
Respiratory distress Respiratory difficulties, Shortness of breath, Short of breath, Difficulty breathing, Breathing difficulties [more] Difficulty in breathing. The physical presentation of respiratory distress is generally referred to as labored breathing, while the sensation of respiratory distress is called shortness of breath or dyspnea.
Myoclonus Jerking, Myoclonic jerks, Involuntary jerking movements [more] Very brief, involuntary random muscular contractions occurring at rest, in response to sensory stimuli, or accompanying voluntary movements.
Pulmonary fibrosis Replacement of normal lung tissues by fibroblasts and collagen.
Congenital hypothyroidism A type of hypothyroidism with congenital onset.
Intellectual disability Nonprogressive intellectual disability, Poor school performance, Mental-retardation, Dull intelligence, Nonprogressive mental retardation, Mental deficiency, Mental retardation, nonspecific, Low intelligence [more] Subnormal intellectual functioning which originates during the developmental period. Intellectual disability, previously referred to as mental retardation, has been defined as an IQ score below 70.

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