Multicentric osteolysis, nodulosis, and arthropathy

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Multicentric osteolysis, nodulosis, and arthropathy (MONA) describes a rare inherited disease characterized by a loss of bone tissue (osteolysis), particularly in the hands and feet. MONA includes a condition formerly called nodulosis-arthropathy-osteolysis (NAO) syndrome. It may also include a similar disorder called Torg syndrome, although it is unknown whether Torg syndrome is actually part of MONA or a separate disorder caused by a mutation in a different gene.

In most cases of MONA, bone loss begins in the hands and feet, causing pain and limiting movement. Bone abnormalities can later spread to other areas of the body, with joint problems (arthropathy) occurring in the elbows, shoulders, knees, hips, and spine. Most people with MONA develop low bone mineral density (osteopenia) and thinning of the bones (osteoporosis) throughout the skeleton. These abnormalities make bones brittle and more prone to fracture. The bone abnormalities also lead to short stature.

Many affected individuals develop subcutaneous nodules, which are firm lumps of noncancerous tissue underneath the skin, especially on the soles of the feet. Some affected individuals also have skin abnormalities including patches of dark, thick, and leathery skin. Other features of MONA can include clouding of the clear front covering of the eye (corneal opacity), excess hair growth (hypertrichosis), overgrowth of the gums, heart abnormalities, and distinctive facial features that are described as "coarse."

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

MONA results from mutations in the MMP2 gene. This gene provides instructions for making an enzyme called matrix metallopeptidase 2, whose primary function is to cut (cleave) a protein called type IV collagen. Type IV collagen is a major structural component of basement membranes, which are thin, sheet-like structures that separate and support cells in many tissues. The activity of matrix metallopeptidase 2 appears to be important for a variety of body functions, including bone remodeling, which is a normal process in which old bone is broken down and new bone is created to replace it.

The MMP2 gene mutations that cause MONA completely eliminate the activity of the matrix metallopeptidase 2 enzyme, preventing the normal cleavage of type IV collagen. It is unclear how a loss of enzyme activity leads to the specific features of MONA. Researchers suspect that it somehow disrupts the balance of new bone creation and the breakdown of existing bone during bone remodeling, resulting in a progressive loss of bone tissue. How a shortage of matrix metallopeptidase 2 leads to the other features of MONA, such as subcutaneous nodules and skin abnormalities, is unknown.

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

MONA is rare; its prevalence is unknown. This condition has been reported in multiple populations worldwide.

Understanding terms used in the source

These definitions explain medical words used above. A definition is not evidence that another condition is present, and it does not predict how a symptom will develop. Ask the clinician which terms apply to the actual examination or test result.

Hypertrichosis

Hypertrichosis is increased hair growth that is abnormal in quantity or location.

Short stature

A height below that which is expected according to age and gender norms. Although there is no universally accepted definition of short stature, many refer to "short stature" as height more than 2 standard deviations below the mean for age and gender (or below the 3rd percentile for age and gender dependent norms).

Osteoporosis

Osteoporosis is a systemic skeletal disease characterized by low bone density and microarchitectural deterioration of bone tissue with a consequent increase in bone fragility. According to the WHO criteria, osteoporosis is defined as a BMD that lies 2.5 standard deviations or more below the average value for young healthy adults (a T-score below -2.5 SD).

Progressive

Applies to a disease manifestation that increases in scope or severity over the course of time, i.e., that worsens with age.

Osteolysis

Osteolysis refers to the destruction of bone through bone resorption with removal or loss of calcium.

Which doctor should you see?

The suggested department for discussing Multicentric osteolysis, nodulosis, and arthropathy is Clinical Genetics, with a clinical geneticist as the relevant type of clinician. Paediatrician (children) or physician (adults), with clinical geneticist referral.

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.

• Does the exact genetic or chromosome finding explain the observed features?
• Would a genetic counsellor help the family understand the result?
• Which organ-specific assessments are appropriate for this particular diagnosis?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Multicentric osteolysis, nodulosis, and arthropathy. 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.