Acromesomelic dysplasia | |
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Other names | Acromesomelic dwarfism [1] |
Specialty | Orthopedic |
Acromesomelic dysplasia is a rare skeletal disorder that causes abnormal bone and cartilage development, leading to shortening of the forearms, lower legs, hands, feet, fingers, and toes. [2] Five different genetic mutations have been implicated in the disorder. Treatment is individualized but is generally aimed at palliating symptoms, for example, treatment of kyphosis and lumbar hyperlordosis. [3]
Acromesomelic dysplasia (AMD) is characterized by the inhibition of growth of certain long bones such as the forearms and lower legs. [3] This disease typically becomes apparent during the first years of life. [3] Forearms, lower legs, hands and feet do not grow proportionally with the rest of the body. [4] Over time, individuals can have a hard time fully extending their arms, rotating the arms inwards towards the body with palms facing down and rotating the arms outward with the palms facing upward. [4] Abnormalities of cartilage and bone development may also cause the bones within the fingers, toes, hands and feet to become sufficiently shorter and broader. [4] During early childhood, individuals may experience progressive, abnormal curvature of the spine. [4] Common symptoms include:
Infants with AMD typically have a normal birth weight, but can have other characteristic facial abnormalities. [3]
AMD is extremely rare and is inherited as an autosomal recessive genetic trait. [3] Autosomal recessive means that two copies of an abnormal gene must be present in order for the disease to develop. [5] This can be inherited from the parents or the gene can mutate in the person who has AMD. [3]
Genetic studies indicate that the mutation at chromosome 9p13-12, for AMD Maroteaux, is a gene that codes for a protein that affects bone development, natriuretic peptide receptor B (Npr2). [3] [6] This is a receptor for the hormone C-type natriuretic peptide which is a hormone that is essential for bone growth. [3] [6] AMD Grebe dysplasia has a gene located at chromosome 20q11.2 [3] [7] This chromosome codes for a protein known as growth and development factor-5 (GDF5). [3] [6] AMD with genital anomalies has a gene located at chromosome 4q23-24; this codes for a protein known as a bone morphogenetic protein receptor, type 1B. [3] [8] Genetic diseases are determined by the combination of genes for a certain trait that is on the chromosomes received from the mother and father. [3]
Dominant genetic disorders happen when a single copy of an abnormal gene is needed to cause a certain disease. [3] The abnormal gene can be inherited from either parent or result from a gene mutation. [3]
The diagnosis is based on a clinical presentation, molecular analysis, electropherogram and radiograph. [9] [3] This disease is diagnosed within the first few years of life. [3] Identification of the main characteristics is the key factor in diagnosis. Molecular analysis is used to examine the DNA of the affected person and their parents. [9] For this, a blood sample is needed and the DNA will be extracted with an automatic DNA extractor. [9] The results will show the mutated chromosome and identify if this chromosome was passed on from a parent. [9] A radiograph will show abnormal growth plates and misshapen bones in the limbs. [6] [3] [9] This can confirm the abnormal development and premature fusion of the regions where the diaphyses, of certain long bones, meet their epiphyses. [3] Electropherogram is used to identify genotyping.[ citation needed ] These results can be used to compare to a normal sequence and relatives sequences. [10]
It is important to have a detailed patient history, including the parents or other relatives. [3] Typically, the parent that carries the chromosome for AMD, seems to be shorter than average. [6] [11] Monitoring the weight and height of the person affected with AMD is important. [10] Based on the person's age, they should be meeting a certain percentile to identify any issues that may be causing a stunt in growth. [3]
There are five types of AMD: [3]
Osebold-Remondini causes shortness of limbs and hypoplasia of the second phalanges with fusion to the remaining phalanges, carpal and tarsal coalitions. [12] Maroteaux type causes severe dwarfism with a height below 120 cm. [6] This type also causes shortening of the middle and distal segments of the limbs. [6] Grebe dysplasia causes extreme abnormalities of the limb joints and limbs. [7] In this type of AMD, the hands and feet are affected the most. [7] This type primarily affects the joints in the hands and feet causing a lack of articulation. [7] Grebe dysplasia does not have any major effects on the stature. [7] Du Pan syndrome causes underdevelopment of the tissues in the fibulae, feet and hands. [13] Acromesomelic dysplasia with genital anomalies causes shortness of limbs and stature with congenital malformations of the female genital tract and male reproductive system. [8]
All five types of AMD are caused by a gene mutation or receiving it from their parents. [3] The differences between the types are the different genes that are affected. The mutated gene for each type is listed in the pathophysiology section.[ citation needed ]
There are a few treatment plans for AMD and each person's results vary. Depending on the type of AMD and the symptoms the person has, their therapy may differ. [3] Physical therapy is aimed to help specific symptoms. [3] For example, abnormal curvature of the spine may be treated by exercises, braces, casts and in severe cases, corrective surgery. [3] It is important to start physical therapy as early as possible to ensure that people with AMD can reach their full potential. [3]
One treatment that can help a person who is affected with AMD is recombinant human growth hormone (rhGH). [3] [14] [15] [10] Recombinant human growth hormones are produced in the pituitary gland and can help spur growth in children and adolescents. [16] It is used in AMD patients to help muscle and bone growth. [14] [15] [10] [16] This treatment is long-term and will not cure this disease, it will only help the patient grow a couple of centimeters. [15] [14] [10] A case study showed a growth velocity of 3.6-4.2 cm/year during this first year of treatment. [14] As well as height improving from 1.2 to 1.8 SD over 5 years of treatment. [14] Another case study was conducted that showed within a year, a patient had an increase of 7.0 cm/year. [15] With this treatment, it is important to start it during the puberty stage. [15] [10] Some patients that have received this treatment, have seen no difference or increase in height. [10] There is no prevention with AMD and not many options for managing the symptoms.[ citation needed ]
Kyphosis is an excessive outward curvature of the spine resulting in a hunch back. [17] Treatment for this disease includes taking pain relievers and osteoporosis medications. [17] Medication for osteoporosis helps strengthen the bones to help prevent any spinal fractures. [17] Lumbar hyperlordosis is a condition that occurs when the lower back region experiences stress or extra weight.[ citation needed ] This causes the lower back to become arched and creates muscle spasms or pain.[ citation needed ] Treatment focuses on stretching the lower back, quads, hip flexors and strengthening the hamstrings, glutes and abdominal muscles.[ citation needed ] Braces may be used to help relieve some stress or pressure on the lower back.[ citation needed ]
Risk factors from taking rhGH include: [16]
Other risk factors that increase the risk of having AMD include a family history of having this condition or a child born from parents who are close blood relatives. [18]
A person diagnosed with AMD will have a normal life expectancy. [19] With this disease, there are no chances of full recovery; it is something that the person will have for their entire life. [4] Abnormal cartilage and bone development can affect many bones in the body. [4] Long term effects include joint pain, arthritis, abnormal curvature of the spine and short stature of limbs and height. [3] [4]
The prevalence of AMD is <1/1000000. [20] Nearly ten million people in the world carry the NPR2 mutated gene (Maroteaux type); only 3500 people in the entire world are affected with AMD. [19] AMD is rare and there are less than 100 reported cases. [18] AMD can be classified as skeletal dysplasia, which approximately occurs in 1 out of 5000 births. [21] This disease affects both males and females as well as any racial or ethnic group. [18] The majority of the case studies involve patients that live in Pakistan, Morocco, or Karnataka. [10] [9] [22] [23] AMD does primarily begin in the first few years of life or as early as the neonatal phase, but it can affect anyone at any age. [3] [18]
The earliest known case of AMD occurred in the late Upper Paleolithic. [24] [25] While AMD would have significantly interfered with the ability to live a hunter-gatherer lifestyle, the individual in question lived until late adolescence, suggesting that they were cared for by the group. [24]
A research study was published in 2022 that established a new type of AMD. In the case study, an exome sequence was performed on two girls that had short stature due to acromesomelic limb shortening. [26] The researchers wanted to determine if protein kinase cGMP-dependent type II gene (PRKG2) had any effect on longitudinal growth in bones. [26] The results showed two homozygous PRKG2 variants: nonsense and a frameshift. [26] These variants alter the downstream mitogen activated protein kinase signaling pathway by failing to phosphorylate c-Raf 1 at Ser43 and reduce activation in response to fibroblast growth factor receptor 2. [26]
Another research study was conducted on mice to find a new treatment for people with AMD (Maroteaux type). [21] The results showed that Npr2 is expressed in osteoblasts and chondrocytes; leading to the conclusion that the disruptions in the growth plate from Npr2, can be a leading cause for AMD. [21] They also found that Npr2 stops the activation of a signaling pathway for MEK/ERK, which is a pathway in the growth plates. [21] The data showed that treatment of a pharmacological inhibitor of MEK/ERK pathway might improve bone growth. [21] The data for this treatment produced promising results. It showed that the drug effectively inhibited MEK/ERK activation. [21] This study was only conducted on mice, but it could potentially be a treatment to help people diagnosed with AMD.[ citation needed ]
There are research studies being conducted to see the effect of rhGH. As stated in the treatment section, results may vary per person. Some patients seem to have an overall positive effect of these hormones and it helps them grow a few more centimeters each year. No other clinical trials are going on for AMD. There is a lack of knowledge or medication that can treat or reverse this disease.[ citation needed ]
Achondroplasia is a genetic disorder with an autosomal dominant pattern of inheritance whose primary feature is dwarfism. It is the most common cause of dwarfism and affects about 1 in 27,500 people. In those with the condition, the arms and legs are short, while the torso is typically of normal length. Those affected have an average adult height of 131 centimetres for males and 123 centimetres (4 ft) for females. Other features can include an enlarged head with prominent forehead and underdevelopment of the midface. Complications can include sleep apnea or recurrent ear infections. Achondroplasia includes the extremely rare short-limb skeletal dysplasia with severe combined immunodeficiency.
Langer–Giedion syndrome (LGS) is a very uncommon autosomal dominant genetic disorder caused by a deletion of a small section of material on chromosome 8. It is named after the two doctors who undertook the main research into the condition in the 1960s. Diagnosis is usually made at birth or in early childhood.
Spondyloperipheral dysplasia is an autosomal dominant disorder of bone growth. The condition is characterized by flattened bones of the spine (platyspondyly) and unusually short fingers and toes (brachydactyly). Some affected individuals also have other skeletal abnormalities, short stature, nearsightedness (myopia), hearing loss, and mental retardation. Spondyloperipheral dysplasia is a subtype of collagenopathy, types II and XI.
Kniest dysplasia is a rare form of dwarfism caused by a mutation in the COL2A1 gene on chromosome 12. The COL2A1 gene is responsible for producing type II collagen. The mutation of COL2A1 gene leads to abnormal skeletal growth and problems with hearing and vision. What characterizes Kniest dysplasia from other type II osteochondrodysplasia is the level of severity and the dumb-bell shape of shortened long tubular bones.
Metachondromatosis is an autosomal dominant, incompletely penetrant genetic disease affecting the growth of bones, leading to exostoses primarily in the hands and feet as well as enchondromas of long bone metaphyses and iliac crests. This syndrome affects mainly tubular bones, though it can also involve the vertebrae, small joints, and flat bones. The disease is thought to affect exon 4 of the PTPN11 gene. Metachondromatosis is believed to be caused by an 11 base pair deletion resulting in a frameshift and nonsense mutation. The disease was discovered and named in 1971 by Pierre Maroteaux, a French physician, when he observed two families with skeletal radiologic features with exostoses and Ollier disease. The observation of one family with five affected people led to the identification of the disease as autosomal dominant. There have been less than 40 cases of the disease reported to date.
Chondrodystrophy refers to a skeletal disorder caused by one of myriad genetic mutations that can affect the development of cartilage. As a very general term, it is only used in the medical literature when a more precise description of the condition is unavailable.
McCune–Albright syndrome is a complex genetic disorder affecting the bone, skin and endocrine systems. It is a mosaic disease arising from somatic activating mutations in GNAS, which encodes the alpha-subunit of the Gs heterotrimeric G protein.
Autosomal recessive multiple epiphyseal dysplasia (ARMED), also called epiphyseal dysplasia, multiple, 4 (EDM4), multiple epiphyseal dysplasia with clubfoot or –with bilayered patellae, is an autosomal recessive congenital disorder affecting cartilage and bone development. The disorder has relatively mild signs and symptoms, including joint pain, scoliosis, and malformations of the hands, feet, and knees.
Multiple epiphyseal dysplasia (MED), also known as Fairbank's disease, is a rare genetic disorder that affects the growing ends of bones. Long bones normally elongate by expansion of cartilage in the growth plate near their ends. As it expands outward from the growth plate, the cartilage mineralizes and hardens to become bone (ossification). In MED, this process is defective.
Pseudoachondroplasia is an inherited disorder of bone growth. It is a genetic autosomal dominant disorder. It is generally not discovered until 2–3 years of age, since growth is normal at first. Pseudoachondroplasia is usually first detected by a drop of linear growth in contrast to peers, a waddling gait or arising lower limb deformities.
Acrodysostosis is a rare congenital malformation syndrome which involves shortening of the interphalangeal joints of the hands and feet, intellectual disability in approximately 90% of affected children, and peculiar facies. Other common abnormalities include short head, small broad upturned nose with flat nasal bridge, protruding jaw, increased bone age, intrauterine growth retardation, juvenile arthritis and short stature. Further abnormalities of the skin, genitals, teeth, and skeleton may occur.
Camurati–Engelmann disease (CED) is a very rare autosomal dominant genetic disorder that causes characteristic anomalies in the skeleton. It is also known as progressive diaphyseal dysplasia. It is a form of dysplasia. Patients typically have heavily thickened bones, especially along the shafts of the long bones. The skull bones may be thickened so that the passages through the skull that carry nerves and blood vessels become narrowed, possibly leading to sensory deficits, blindness, or deafness.
Parkes Weber syndrome (PWS) is a congenital disorder of the vascular system. It is an extremely rare condition, and its exact prevalence is unknown. It is named after British dermatologist Frederick Parkes Weber, who first described the syndrome in 1907.
Donohue syndrome is an extremely rare and severe genetic disorder. Leprechaunism derives its name from the hallmark elvish features exhibited by the affected individuals. The disease is caused by a mutation in the INSR gene, which contains the genetic information for the formation of insulin receptors. As a result, affected individuals have either a decreased number of insulin receptors, or insulin receptor with greatly impaired functionality. The lack and impairment of insulin receptor functionality leads to an inability to regulate blood glucose levels through severe insulin resistance. This will ultimately lead to affected development of tissues and organs throughout the body. In addition to the physical abnormalities, leprechaunism is also characterized by endocrine system abnormalities that can lead to conditions such as hyperglycemia, hypoglycemia, hyperinsulemia, and the enlargement of certain sex organs such as the penis in males, and the clitoris in females.
Parastremmatic dwarfism is a rare bone disease that features severe dwarfism, thoracic kyphosis, a distortion and twisting of the limbs, contractures of the large joints, malformations of the vertebrae and pelvis, and incontinence. The disease was first reported in 1970 by Leonard Langer and associates; they used the term parastremmatic from the Greek parastremma, or distorted limbs, to describe it. On X-rays, the disease is distinguished by a "flocky" or lace-like appearance to the bones. The disease is congenital, which means it is apparent at birth. It is caused by a mutation in the TRPV4 gene, located on chromosome 12 in humans. The disease is inherited in an autosomal dominant manner.
Kenny-Caffey syndrome type 2 (KCS2) is an extremely rare autosomal dominant genetic condition characterized by dwarfism, hypermetropia, microphthalmia, and skeletal abnormalities. This subtype of Kenny-Caffey syndrome is caused by a heterozygous mutation in the FAM111A gene (615292) on chromosome 11q12.
Dysosteosclerosis (DSS), also known as autosomal recessive dysosteosclerosis or X-linked recessive dysosteosclerosis, is a rare osteoclast-poor form of osteosclerosis that is presented during infancy and early childhood, characterized by progressive osteosclerosis and platyspondyly. Platyspondyly and other skeletal abnormalities are radiographic features of the disease which distinguish DSS from other osteosclerotic disorders. Patients usually experience neurological and psychological deterioration, therefore patients are commonly associated with delayed milestones.
Du Pan syndrome, also known as fibular aplasia-complex brachydactyly syndrome, is an extremely rare genetic condition. Unlike other rare genetic conditions, Du Pan syndrome does not affect brain function or the appearance of the head and trunk. This condition is associated with alterations to the GDF5 gene. The way that this condition is passed on from generation to generation varies, but it is most commonly inherited in an autosomal recessive manner, meaning two copies of the same version of the gene are required to show this condition. Rare cases exist where the mode of inheritance is autosomal dominant, which means only one version of the gene is necessary to have the condition.
Spondyloenchondrodysplasia is the medical term for a rare spectrum of symptoms that are inherited following an autosomal recessive inheritance pattern. Skeletal anomalies are the usual symptoms of the disorder, although its phenotypical nature is highly variable among patients with the condition, including symptoms such as muscle spasticity or thrombocytopenia purpura. It is a type of immunoosseous dysplasia.