Mandibuloacral dysplasia

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Mandibuloacral dysplasia is a condition that causes a variety of abnormalities involving bone development, skin coloring (pigmentation), and fat distribution. People with this condition may grow slowly after birth. Most affected individuals are born with an underdeveloped lower jaw bone (mandible) and small collar bones (clavicles), leading to the characteristic features of a small chin and sloped shoulders. Other bone problems include loss of bone from the tips of the fingers (acroosteolysis), which causes bulbous finger tips; delayed closure of certain skull bones; and joint deformities (contractures).

People with mandibuloacral dysplasia can have mottled or patchy skin pigmentation or other skin abnormalities. Some people with this condition have features of premature aging (a condition called progeria), such as thin skin, loss of teeth, loss of hair, and a beaked nose. Some individuals with mandibuloacral dysplasia have metabolic problems, such as diabetes.

A common feature of mandibuloacral dysplasia is a lack of fatty tissue under the skin (lipodystrophy) in certain regions of the body. The two types of this disorder, mandibuloacral dysplasia with type A lipodystrophy (MADA) and mandibuloacral dysplasia with type B lipodystrophy (MADB) are distinguished by the pattern of fat distribution throughout the body. Type A is described as partial lipodystrophy; affected individuals have a loss of fatty tissue from the torso and limbs, but it may build up around the neck and shoulders. Type B is a generalized lipodystrophy, with loss of fatty tissue in the face, torso, and limbs.

MADA usually begins in adulthood, although children can be affected. MADB begins earlier, often just after birth. Many babies with MADB are born prematurely.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

The two forms of mandibuloacral dysplasia are caused by mutations in different genes. Mutations in the LMNA gene cause MADA, and mutations in the ZMPSTE24 gene cause MADB. Within cells, these genes are involved in maintaining the structure of the nucleus and may play a role in many cellular processes.

The LMNA gene provides instructions for making two related proteins, lamin A and lamin C. These proteins act as scaffolding (supporting) components of the nuclear envelope, which is the membrane that surrounds the nucleus in cells. The nuclear envelope regulates the movement of molecules into and out of the nucleus and may help regulate the activity of certain genes. Mutations in this gene likely change the structure of lamin A and lamin C.

The lamin A protein (but not lamin C) must be processed within the cell before becoming part of the nuclear envelope. The protein produced from the ZMPSTE24 gene is involved in this processing; it cuts the immature lamin A protein (prelamin A) at a particular location, forming mature lamin A. Mutations in the ZMPSTE24 gene lead to a buildup of prelamin A and a shortage of the mature protein.

Mutations in the LMNA or ZMPSTE24 gene likely disrupt the structure of the nuclear envelope. Researchers are working to understand how these genetic changes result in the signs and symptoms of mandibuloacral dysplasia.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Mandibuloacral dysplasia is a rare condition; its prevalence is unknown.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Abnormality of skin pigmentation · Very frequent (99-80%)

An abnormality of the pigmentation of the skin.

Full cheeks · Very frequent (99-80%)

Increased prominence or roundness of soft tissues between zygomata and mandible.

High palate · Very frequent (99-80%)

Height of the palate more than 2 SD above the mean (objective) or palatal height at the level of the first permanent molar more than twice the height of the teeth (subjective).

Hyperinsulinemia · Very frequent (99-80%)

An increased concentration of insulin in the blood.

Increased adipose tissue around the neck · Very frequent (99-80%)

An increased amount of subcutaneous fat tissue around the neck.

Insulin resistance · Very frequent (99-80%)

Increased resistance towards insulin, that is, diminished effectiveness of insulin in reducing blood glucose levels.

Lipoatrophy · Very frequent (99-80%)

Localized loss of fat tissue.

Loss of subcutaneous adipose tissue in limbs · Very frequent (99-80%)

Loss (disappearance) of previously present subcutaneous fat tissue in arm or leg.

Other findings in the same source

From: Orphanet

Additional reported features include Micrognathia (Very frequent (99-80%)); Narrow nose (Very frequent (99-80%)); Thin skin (Very frequent (99-80%)); Contractures of the large joints (Very frequent (99-80%)); Abnormal tongue morphology (Frequent (79-30%)); Abnormally large globe (Frequent (79-30%)); Acanthosis nigricans (Frequent (79-30%)); Alopecia (Frequent (79-30%)); Delayed cranial suture closure (Frequent (79-30%)); Dental crowding (Frequent (79-30%)). This is a selected summary, not a complete description of the condition.

Which doctor should you see?

The suggested department for discussing Mandibuloacral dysplasia is Orthopaedics, with a orthopaedic specialist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• What explains the change in pain, movement or function?
• Which activities need adjustment while the diagnosis is being clarified?
• What are the roles of rehabilitation, observation and surgery in this situation?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Mandibuloacral dysplasia. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.