Acalvaria usually occurs in less than 1 of every 100,000 births. By way of epidemiological data, it is thought that females are more prone to have this defect. Currently, acalvaria is not thought to have much of a risk of recurrence.

Prognosis is poor. Previous research suggested a 100% mortality rate for those with acrania. This disease is rare, occurring in 1 in 20,000 live births.

In order to better manage an acrania diagnosis, early detection is of extreme importance so that actions may be taken to help the mother and child. Families may choose either to terminate the pregnancy, or to carry the child to term. Acrania may cause a fetus to spontaneously abort before reaching term.

Usually babies with this malformation do not survive past birth. However, there have been cases of survival. As of 2004, there were only two reported living cases. Of these two, one was severely cognitively impaired and physically disabled. The status of the other was unreported. If the fetus progresses to full term, there is the risk that it will have head trauma from the pressure applied to the head while being delivered. A few other cases of acalvaria have been reported, which did not progress to birth. In addition to the lack skull cap, there were brain malformations present in each case, and all of the pregnancies were terminated either electively or the fetuses were spontaneously aborted.

Osteogenesis imperfecta is a rare condition in which bones break easily. There are multiple genetic mutations in different genes for collagen that may result in this condition. It can be treated with some drugs to promote bone growth, by surgically implanting metal rods in long bones to strengthen them, and through physical therapy and medical devices to improve mobility.

Congenital causes include:

- Klippel Trenaunay Weber syndrome

- Maffucci syndrome

- macrodystrophia lipomatosa

- neurofibromatosis,

- lipoatrophic diabetes.

- Proteus syndrome, which by one theory accounts for the deformities of the Elephant Man

There are a number of acquired causes of local gigantism. A body part can attain bigger size from causes as common as the following:

- inflammation, due to trauma or infection

- tumors like osteoid osteoma, melorheostosis, and lipofibromatous hamartoma

- Arteriovenous malformations occurring on a limb, before the closure of epiphyses in long bones

- Elephantiasis, which is quite common in south-east asia due to prevalence of filariasis.

- Still's disease

- amyloidosis

- acromegaly

Little genetic counseling can be offered for acrania because the genetic origins are not fully understood. In order to make genetic counseling for families easier this disease is often differentially diagnosed with other diseases that can occur at the same time such as anencephaly and acalvaria, though these diseases may not always occur simultaneously. While this disease is tragic, reoccurrence rates are extremely low so genetic counseling is not always necessary.

The autosomal dominant form is caused by a mutation in ANKH on chromosome 5 (5p15.2-p14.1). The autosomal recessive form is caused by a mutation in a mutation in GJA1 on chromosome 6 (6q21-q22). The recessive form tends to be more severe than the dominant form.

The only treatment for this disorder is surgery to reduce the compression of cranial nerves and spinal cord. However, bone regrowth is common since the surgical procedure can be technically difficult. Genetic counseling is offered to the families of the people with this disorder.

Katz Syndrome is a rare congenital disorder, presenting as a polymalformative syndrome characterized by enlarged viscera, hepatomegaly, diabetes, and skeletal anomalies that result in a short stature, cranial hyperostosis, and typical facial features. It is probably a variant of the autosomal recessive type of Craniometaphyseal Dysplasia.

Incidence of Crouzon syndrome is currently estimated to occur in 1.6 out of every 100,000 people. There is a greater frequency in families with a history of the disorder, but that doesn't mean that everyone in the family is affected (as referred to above).

Environmental factors refer for example to maternal smoking and the maternal exposure to amine-containing drugs. Several research groups have found evidence that these environmental factors are responsible for an increase in the risk of craniosynostosis, likely through effects on fibroblast growth factor receptor genes.

On the other hand, a recent evaluation of valproic acid (an anti-epilepticum), which has been implicated as a causative agent, has shown no association with craniosynostosis.

Certain medication (like amine-containing drugs) can increase the risk of craniosynostosis when taken during pregnancy, these are so-called teratogenic factors.

Macrocephaly may be pathological, but many people with abnormally large heads or large skulls are healthy. Pathologic macrocephaly may be due to megalencephaly (enlarged brain), hydrocephalus (water on the brain), cranial hyperostosis (bone overgrowth), and other conditions. Pathologic macrocephaly is called "syndromic" when it is associated with any other noteworthy condition, and "nonsyndromic" otherwise. Pathologic macrocephaly can be caused by congenital anatomic abnormalities, genetic conditions, or by environmental events.

Many genetic conditions are associated with macrocephaly, including familial macrocephaly related to the holgate gene, autism, "PTEN" mutations such as Cowden disease, neurofibromatosis type 1, and tuberous sclerosis; overgrowth syndromes such as Sotos syndrome (cerebral gigantism), Weaver syndrome, Simpson-Golabi-Behmel syndrome (bulldog syndrome), and macrocephaly-capillary malformation (M-CMTC) syndrome; neurocardiofacial-cutaneous syndromes such as Noonan syndrome, Costello syndrome, Gorlin Syndrome, (also known as Basal Cell Nevus Syndrome) and cardiofaciocutaneous syndrome; Fragile X syndrome; leukodystrophies (brain white matter degeneration) such as Alexander disease, Canavan disease, and megalencephalic leukoencephalopathy with subcortical cysts; and glutaric aciduria type 1 and D-2-hydroxyglutaric aciduria.

At one end of the genetic spectrum, duplications of chromosomes have been found to be related to autism and macrocephaly; at the other end, deletions of chromosomes have been found to be related to schizophrenia and microcephaly.

Environmental events associated with macrocephaly include infection, neonatal intraventricular hemorrhage (bleeding within the infant brain), subdural hematoma (bleeding beneath the outer lining of the brain), subdural effusion (collection of fluid beneath the outer lining of the brain), and arachnoid cysts (cysts on the brain surface).

Macrocephaly is a condition in which the head is abnormally large; this includes the scalp, the cranial bone, and the contents of the cranium.

"Achondroplasia" is a type of autosomal dominant genetic disorder that is the most common cause of dwarfism. Achondroplastic dwarfs have short stature, with an average adult height of 131 cm (4 feet, 3 inches) for males and 123 cm (4 feet, 0 inches) for females.

The prevalence is approximately 1 in 25,000 births.

Manifestations include enlarged viscera, hepatomegaly, diabetes, short stature and cranial hyperostosis.

Porotic hyperostosis, also known as osteoporosis symmetrica, cribra crani, hyperostosis spongiosa, and symmetrical osteoporosis is a pathological condition that affects bones of the cranial vault, and is characterized by localized areas of spongy or porous bone tissue. The diploë, or spongy tissue within the bones of the cranium, swells and the tissue of the outer surface becomes thinner and more porous in appearance.

This condition was widely accepted as a result of anemia, which is typically due to an iron deficient diet, but several lines of evidence suggest that the accelerated loss and compensatory over-production of red blood cells seen in hemolytic and megaloblastic anemia are the most likely proximate causes of porotic hyperostosis.

In anthropology, the presence of the condition has been considered evidence that a past population suffered chronic or episodic malnutrition. Anthropologists examine bones of past populations to learn about their lifestyles. A sub-discipline known as paleonutrition has focused on the presence of porotic hyperostosis, among other nutritional disorders. A high incidence of the disease indicates the population adapted poorly to its environment or was under nutritional stress. A low level of iron in the blood is also a defense against pathogens, so a high incidence of the disease in a population could also indicate an attempt to fight off an infectious disease. From this perspective, porotic hyperostosis could be viewed as a biological attempt to adapt to the environment, rather than an indicator of malnutrition.

An osteoma (plural: "osteomata") is a new piece of bone usually growing on another piece of bone, typically the skull. It is a benign tumor.

When the bone tumor grows on other bone it is known as "homoplastic osteoma"; when it grows on other tissue it is called "heteroplastic osteoma".

Osteoma represents the most common benign neoplasm of the nose and paranasal sinuses. The cause of osteomata is uncertain, but commonly accepted theories propose embryologic, traumatic, or infectious causes. Osteomata are also found in Gardner's syndrome. Larger craniofacial osteomata may cause facial pain, headache, and infection due to obstructed nasofrontal ducts. Often, craniofacial osteoma presents itself through ocular signs and symptoms (such as proptosis).

Biomechanical factors include fetal head constraint during pregnancy. It has been found by Jacob et al. that constraint inside the womb is associated with decreased expression of Indian Hedgehog protein and noggin. These last two are both important factors influencing bone development.

Calcinosis may result from a variety of causes such as:

- Trauma to the region

- Inflammation (bug bites, acne)

- Varicose veins

- Infections

- Tumors (malignant or benign)

- Diseases of connective tissue

- Hypercalcemia

- Hyperphosphatemia

Calicinosis cutis is associated with systemic sclerosis.

Paget's disease may be caused by a slow virus infection (i.e., paramyxoviridae) present for many years before symptoms appear. Associated viral infections include respiratory syncytial virus, canine distemper virus, and the measles virus. However, recent evidence has cast some doubt upon the measles association. Laboratory contamination may have played a role in past studies linking paramyxovirus (e.g. measles) to Paget's disease.

A male with pseudohypoparathyroidism has a 50% chance of passing on the defective GNAS gene to his children, although in an imprinted, inactive form. Any of his children receiving this gene will have pseudopseudohypoparathyroidism. Any of his daughters that have pseudopseudohypoparathyroidism may in turn pass along pseudohypoparathyroidism 1A to her children as the imprinting pattern on the inherited paternal gene will be changed to the maternal pattern in the mother's ovum during meiosis. The gene will be reactivated in any children who inherit it.

Pseudopseudohypoparathyroidism and pseudohypoparathyroidism both involve the same GNAS gene, but pseudopseudohypoparathyroidism has normal calcium homeostasis because of the normal maternal allele in the kidney.

Treatments focuses on symptoms, with genetic counseling recommended.

The disease is progressive and slowly worsens with time, although people may remain minimally symptomatic. Treatment is aimed at controlling symptoms, but there is no cure. Any bone or bones can be affected, but Paget's disease occurs most frequently in the spine, skull, pelvis, femur, and lower legs.

Osteogenic sarcoma, a form of bone cancer, is a rare complication of Paget's disease occurring in less than one percent of those affected. The development of osteosarcoma may be suggested by the sudden onset or worsening pain.

Calcinosis cutis may be divided into the following types:

- Dystrophic calcinosis cutis

- Metastatic calcinosis cutis

- Iatrogenic calcinosis cutis

- Traumatic calcinosis cutis

- Idiopathic calcinosis cutis

- Idiopathic scrotal calcinosis

- Subepidermal calcified nodule

- Tumoral calcinosis

- Osteoma cutis