Amastia refers to a rare clinical anomaly in which both internal breast tissue and the visible nipple are absent on one or both sides. It affects both men and women. Amastia can be either isolated (the only medical condition) or comorbid with other syndromes, such as ectodermal dysplasia, Syndactyly (Poland's syndrome) and lipoatrophic diabetes. [1] This abnormality can be classified into various types, and each could result from different pathologies. [2] Amastia differs from amazia and athelia. Amazia is the absence of one or both mammary glands but the nipples remain present, and athelia is the absence of one or both nipples, but the mammary gland remains. [3]
Amastia is presumably due to failure of embryologic (before birth) mammary ridge development or incomplete involution. People with amastia often suffer from ectodermal defects, which include various syndromes such as cleft palate, isolated pectoral muscle and abnormal formation of the arms. [4]
Treatment for female amastia particularly includes psychological guidance and breast reconstruction. [1] Because there is no breast tissue, breastfeeding is not possible. If amastia only appears on one side, then it is possible to breastfeed on the other side. Often, people with amastia decide against treatment.
Amastia can be either iatrogenic or congenital. [1] The congenital amastia are further divided into syndromic type and non-syndromic type respectively.
As the definition suggests, syndromic amastia is often associated with obvious symptoms. The common case is hypoplasia of ectodermal tissue, such as hair and skin defects.
On the other hand, non-syndromic amastia, shows no defects in body parts other than breast. This type of amastia can be further classified into unilateral and bilateral amastia. Unilateral amastia can be defined as amastia involving only one side of breast, while bilateral type refers to amastia on both sides of breast. [5] Unilateral amastia is less common than bilateral amastia. Almost all the non-syndromic amastia patients are female. [6]
Typically, amastia patients have both their nipple and areola missing, and the nipple may be absent on one or both sides of the breasts. Abnormalities are not often associated with the breasts. However, symptoms such as hypertelorism, saddle nose, cleft palate, urologic disorders and dysfunction of muscle, upper and lower limb have been observed. Sometimes several members of a family can be diagnosed as amastia simultaneously, all of them are carriers of mutations in TBX3 gene. This mutation could cause various abnormalities, not only amastia, but also deformation of limb and teeth. [4] [6]
Cases of unilateral amastia are uncommon, and they are often associated with hypoplasia of pectoral major muscle and/or the thorax. Bilateral amastia is more common because it is often associated with other different syndromes. Therefore, the symptoms of bilateral amastia are easier to be diagnosed. [5] Various associated syndromes are listed below.
Amastia, particularly if it is bilateral, often related to various syndromes, including ectodermal dysplasia and Poland's syndrome, which is characterised by anomalies of underlying mesoderm and abnormal pectoral muscle respectively. [7] Other syndromes, such as FIG4 associated Yunis Varon syndrome (MIM 216340), acro-der-mato-ungual-lacrimal-tooth (ADULT) syndrome, TP63 associated limb mammary syndrome (MIM 603543), TBX3 associated ulnar syndrome (MIM 181450) and KCTD1 associated scalp-ear-nipple syndrome (MIM 181270) have also been clinically observed. [3]
Ectodermal dysplasia is commonly associated with syndromic amastia. The symptoms of ectodermal dysplasia can be referred to abnormal development of several ectodermal-derived structure such as hair, teeth, nails and sweat glands. Other symptoms may include the inability to sweat, vision or hearing loss, missing or underdeveloped fingers or toes and maldevelopment of breast tissue. Genetic mutations may cause ectodermal dysplasia, and these genes can pass from parents to children. The most common case is the mutation of EDA1 gene which is in X chromosome, and this mutation results in X-linked form hypohidrotic ectodermal dysplasia (XLHED). There is strong association between amastia and XLHED. Over 30% male patients with XLHED have absent nipples. 79% female carriers decrease the ability of breastfeeding. This suggests people with amastia should have a comprehensive skin test to exclude this syndrome. [7]
Poland's syndrome is a genetic disorder associated with abnormal breast development. The prevalence rate of this syndrome is approximately 1 in 20000 to 30000. Both chest wall and upper limb lost normal function, and this syndrome usually occurs unilaterally. Mild and partial forms of Poland's syndrome are common, which often been undiagnosed because the clinical feature is only breast asymmetry and a horizontal anterior axillary fold, without severe symptoms. Other abnormalities include deformation of ribs, absence of pectoralis muscle, hypoplasia or abnormalities of breast and subcutaneous tissue. Patients may also have webbed fingers on one hand, short bones in the forearm or sparse underarm hair. [2] [8]
Al Awadi/Raas-Rothschild syndrome is a rare genetic disorder. Symptoms are often associated with absence or maldevelopment of skeletal part of limbs. [9]
As the name suggests, Scalp-ear-nipple syndrome is characterized by congenital absence of skin, abnormalities of scalp, malformation of ear structures, and undeveloped nipples. [9]
Mammary glands are arranged in breasts of the primates to produce milk for feeding offspring. They are enlarged and modified sweat glands. In the embryological development, mammary glands firstly appear after six weeks of pregnancy in the form of ectodermal ridges. The ectodermal ridge grows thicker and compresses to form mesoderm. As the proliferation persists, mesodermal layer continues to form clusters. The clusters grow and become lobules. At the same time, the clusters also form a pit, which protrudes to generate the nipples. Impairment in some of these processes may cause aplasia of the breast tissue, which may result in amastia. [5]
For example, in normal condition, mammary ridge (milk line) would extend from the bilateral axillary tail to the inguinal region. If this extension does not occur in normal way, the breast would not develop successfully. [4] [7]
Amastia may also be caused by the inability of producing parathyroid hormone related protein. The absence of this protein will disrupt the normal development of mammary gland. Therefore, when amastia patients receive medical ultrasound examination, asymmetry or disproportioned mammary tissue may be found. [9]
Unilateral amastia is usually caused by Poland's syndrome, which is characterized by one side absence of breast. The absence or dysfunction of pectoralis muscle and ribs are common case. It can also be part of other syndromes as described in the previous contents.
Other causes may include intrauterine exposure to teratogenic drugs such as Dehydroepiandrosterone and methimazole / carbimazole treatment during first trimester. [1]
For bilateral amastia, the cause has not been well understood so far. It may be related to gene mutation since often patients with bilateral amastia are diagnosed as autosomal dominant and recessive inheritance. Decreasing blood flow in the subclavian artery may also be a cause of amastia. [1]
Amastia can also be caused by injuries. These injuries may happen when patients receive surgery, such as thoracotomy, chest tube placement, or when they are treated by radiotherapy. Improper biopsy or severe burns of breast tissue may also result in amastia. [10]
Congenital amastia can be associated with both autosomal dominant and recessive inheritance. However, in clinical research, autosomal recessive heritage amastia is uncommon. [3]
Mutation of genes may disrupt the normal process and results in abnormity of breast. The protein tyrosine receptor type F gene (PTPRF) is particularly important in nipple-areola region development. PTPRF encodes protein phosphatase which can localize at adherent junction. This phosphatase may also regulate epithelial cell to enable cell- cell interaction. PTPRF is also responsible for growth factor signalling and Wnt pathway. Homozygous frameshift mutation in PTPRF may cause amastia, which suggests the causative relationship between PTPRF defect and syndromic amastia. [3]
Since bilateral and unilateral amastia may be attributed to different pathologies, appropriate managements should be adopted accordingly. Bilateral amastia can occur in isolation or associated with other disorders. This case is less understood and difficult to treat. On the other hand, Poland's syndrome is the most common cause of unilateral amastia. Managements such as muscle/breast reconstruction and nipple areola relocation should be provided to these patients. [2]
Surgical treatment for breast defects such as mastectomy is also applicable to treat patients with amastia. Tissue expansion is the most common technique and can be done by using either autologous or prosthetic tissue. For autologous reconstruction, different tissues may be chosen according to patients’ physical condition or their preferences. Prosthetic reconstruction may follow the same principles. [2] Flap reconstruction is another method to rebuild the breast surgically. There are various kinds of flaps to choose depending on different situation. [5]
Amastia is often associated with Poland's syndrome, which requires appropriate reconstructive procedure to stabilize chest wall, transfer dynamic muscle and reposition nipple areola region. The treatment of nipple areola relocation provides space for secondary breast enlargement. In this treatment, the tissue expander can be inserted either beforehand or delayed. It can be placed in different parts of body depending on how many overlying soft tissues the patient has. In order to guide the dissection and make sure the correct location of these tissues, marking of the inframammary crease is required before operation. [2]
Septo-optic dysplasia (SOD), known also as de Morsier syndrome, is a rare congenital malformation syndrome that features a combination of the underdevelopment of the optic nerve, pituitary gland dysfunction, and absence of the septum pellucidum . Two or more of these features need to be present for a clinical diagnosis—only 30% of patients have all three. French-Swiss doctor Georges de Morsier first recognized the relation of a rudimentary or absent septum pellucidum with hypoplasia of the optic nerves and chiasm in 1956.
Arthrogryposis (AMC) describes congenital joint contracture in two or more areas of the body. It derives its name from Greek, literally meaning 'curving of joints'.
Ectodermal dysplasia (ED) is a group of genetic syndromes all deriving from abnormalities of the ectodermal structures. More than 150 different syndromes have been identified.
Van der Woude syndrome (VDWS) is a genetic disorder characterized by the combination of lower lip pits, cleft lip with or without cleft palate (CL/P), and cleft palate only (CPO). The frequency of orofacial clefts ranges from 1:1000 to 1:500 births worldwide, and there are more than 400 syndromes that involve CL/P. VWS is distinct from other clefting syndromes due to the combination of cleft lip and palate (CLP) and CPO within the same family. Other features frequently associated with VWS include hypodontia in 10-81% of cases, narrow arched palate, congenital heart disease, heart murmur and cerebral abnormalities, syndactyly of the hands, polythelia, ankyloglossia, and adhesions between the upper and lower gum pads.
An inverted nipple is a condition where the nipple, instead of pointing outward, is retracted into the breast. In some cases, the nipple will be temporarily protruded if stimulated. Both women and men can have inverted nipples.
Sturge–Weber syndrome, sometimes referred to as encephalotrigeminal angiomatosis, is a rare congenital neurological and skin disorder. It is one of the phakomatoses and is often associated with port-wine stains of the face, glaucoma, seizures, intellectual disability, and ipsilateral leptomeningeal angioma. Sturge–Weber syndrome can be classified into three different types. Type 1 includes facial and leptomeningeal angiomas as well as the possibility of glaucoma or choroidal lesions. Normally, only one side of the brain is affected. This type is the most common. Type 2 involvement includes a facial angioma with a possibility of glaucoma developing. There is no evidence of brain involvement. Symptoms can show at any time beyond the initial diagnosis of the facial angioma. The symptoms can include glaucoma, cerebral blood flow abnormalities and headaches. More research is needed on this type of Sturge–Weber syndrome. Type 3 has leptomeningeal angioma involvement exclusively. The facial angioma is absent and glaucoma rarely occurs. This type is only diagnosed via brain scan.
Poland syndrome is a birth defect characterized by an underdeveloped chest muscle and short webbed fingers on one side of the body. There may also be short ribs, less fat, and breast and nipple abnormalities on the same side of the body. Typically, the right side is involved. Those affected generally have normal movement and health.
Micromastia is a medical term describing the postpubertal underdevelopment of a woman's breast tissue. Just as it is impossible to define 'normal' breast size, there is no objective definition of micromastia. Breast development is commonly asymmetric and one or both breasts may be small. This condition may be a congenital defect associated with underlying abnormalities of the pectoral muscle, related to trauma or it may be a more subjective aesthetic description.
Anodontia is a rare genetic disorder characterized by the congenital absence of all primary or permanent teeth. It is divided into two subsections, complete absence of teeth or only some absence of teeth. It is associated with the group of skin and nerve syndromes called the ectodermal dysplasias. Anodontia is usually part of a syndrome and seldom occurs as an isolated entity. There is usually no exact cause for anodontia. The defect results in the dental lamina obstruction during embryogenesis due to local, systemic and genetic factors.
Duane-radial ray syndrome, also known as Okihiro Syndrome, is a rare autosomal dominant disorder that primarily affects the eyes and causes abnormalities of bones in the arms and hands. This disorder is considered to be a SALL4-related disorder due to the SALL4 gene mutations leading to these abnormalities. It is diagnosed by clinical findings on a physical exam as well as genetic testing and imaging. After being diagnosed, there are other evaluations that one may go through in order to determine the extent of the disease. There are various treatments for the symptoms of this disorder.
Ectrodactyly–ectodermal dysplasia–cleft syndrome, or EEC, and also referred to as EEC syndrome and split hand–split foot–ectodermal dysplasia–cleft syndrome is a rare form of ectodermal dysplasia, an autosomal dominant disorder inherited as a genetic trait. EEC is characterized by the triad of ectrodactyly, ectodermal dysplasia, and facial clefts. Other features noted in association with EEC include vesicoureteral reflux, recurrent urinary tract infections, obstruction of the nasolacrimal duct, decreased pigmentation of the hair and skin, missing or abnormal teeth, enamel hypoplasia, absent punctae in the lower eyelids, photophobia, occasional cognitive impairment and kidney anomalies, and conductive hearing loss.
Hypohidrotic ectodermal dysplasia is one of about 150 types of ectodermal dysplasia in humans. Before birth, these disorders result in the abnormal development of structures including the skin, hair, nails, teeth, and sweat glands.
Papillorenal syndrome is an autosomal dominant genetic disorder marked by underdevelopment (hypoplasia) of the kidney and colobomas of the optic nerve.
Amazia refers to a condition where one or both of the mammary glands is absent. This may occur either congenitally or iatrogenically. Amazia can be treated with breast implants.
Hay–Wells syndrome is one of at least 150 known types of ectodermal dysplasia. These disorders affect tissues that arise from the ectodermal germ layer, such as skin, hair, and nails.
EEM syndrome is an autosomal recessive congenital malformation disorder affecting tissues associated with the ectoderm, and also the hands, feet and eyes.
Johanson–Blizzard syndrome is a rare, sometimes fatal autosomal recessive multisystem congenital disorder featuring abnormal development of the pancreas, nose and scalp, with intellectual disability, hearing loss and growth failure. It is sometimes described as a form of ectodermal dysplasia.
Supernumerary nipples–uropathies–Becker's nevus syndrome is a skin condition that may be associated with genitourinary tract abnormalities. Supernumerary nipples, also referred to as polythelia or accessory nipples, is a pigmented lesion of the skin that is present at birth. This pigmentation usually occurs along the milk lines, which are the precursors to breast and nipple development. Clinically, this congenital condition is generally considered benign, but some studies have suggested there may be an association with kidney diseases and cancers of the urogenital system.
Acro–dermato–ungual–lacrimal–tooth syndrome is a rare genetic disease. It is an autosomal dominant form of ectodermal dysplasia, a group of disorders that affects the hair, teeth, nails, sweat glands, and extremities. The syndrome arises from a mutation in the TP63 gene. This disease was previously thought to be a form of ectrodactyly–ectodermal dysplasia–cleft syndrome (EEC), but was classified as a different disease in 1993 by Propping and Zerres.
Odontoonychodermal dysplasia is a rare genetic disorder which is characterized by systemic abnormalities of the teeth, the nails of the fingers and toes, the skin, the hair cells, and the sweat glands. It is a type of syndromic ectodermal dysplasia.