What is Hypertrophic Osteoarthropathy?
Hypertrophic osteoarthropathy (HOA) is a condition that includes symptoms like thickening of your fingers or toes (known as “digital clubbing”), changes in your long bones, joint pain, and swelling. It involves abnormal growth in the skin, tissues, and bones at the ends of your limbs. There are two types of this disease, primary and secondary. Primary HOA is also known as pachydermoperiostosis, and includes symptoms like digital clubbing, changes in the outer layer of your bones (known as periostosis), and thickened skin. It’s a rare disease that is passed down in families through genes. On the other hand, secondary HOA occurs due to certain lung, heart, or other conditions.
Clubbing is a sign that doctors have recognized for a very long time, first noted in a man with curved fingernails and a type of pus-filled infection in the lungs by Hippocrates, a famous Greek physician, around 2,500 years ago. In 1868, Friedreich was the first to scientifically describe primary HOA, referring to it as “hyperostosis of the entire skeleton” in reference to two brothers who had the disease. Later, in 1935, a team of three doctors, named Touraine, Solente, and Gole, established the term Primary HOA to separate the disease that occurs on its own from the one that occurs as a result of an underlying illness like lung or heart disease.
What Causes Hypertrophic Osteoarthropathy?
Hypertrophic osteoarthropathy (HOA), a type of joint disorder, can be connected to many internal diseases, particularly those affecting the lungs and heart. It has also been found as a related condition to problems in the digestive system and hormone disorders. When it’s connected to these other diseases, it’s called secondary hypertrophic osteoarthropathy. Lung cancer, especially a type called non-small cell lung cancer, is most frequently related to HOA. When this happens, it’s considered a paraneoplastic rheumatic syndrome, which is a condition that occurs as an indirect result of cancer in the body. In contrast, primary hypertrophic osteoarthropathy (PHO) is a genetic disorder and its direct cause isn’t known.
Risk Factors and Frequency for Hypertrophic Osteoarthropathy
The exact number of cases and the commonality of PHO, a type of disease, is not currently known. This disease seems to show up in two main age groups – initially in the first year of a person’s life, and then again during puberty. It appears that males are primarily the ones affected. Studies have shown that the disease can be passed down through families in two ways: either by autosomal dominant or autosomal recessive inheritance.
Signs and Symptoms of Hypertrophic Osteoarthropathy
Primary Hypertrophic Osteoarthropathy (PHO) is a medical condition where most patients could show symptoms of digital clubbing, a distinct change in the shape of your fingertips. In mild or early cases, clubbing might be the only symptom. During a physical examination, a doctor might notice a particular bulb-like or “drumstick” change to the tips of your fingers or even your toes.
The nails of affected individuals will start curving out more and the skin at the base of the nail becomes shiny and thin. The fingertips may also lose their normal creases. You might feel a certain rocking or instability of the nail bed due to increased swelling and soft tissue.
The Lovibond profile sign is a clinical technique used to diagnose clubbing and to differentiate it from similar conditions. A Lovibond sign is considered positive for clubbing if there’s an increase in the angle between the base of the nail and the nail itself which is more than 180 degrees. This could result in a condition known as Schamroth sign, where the diamond-shaped window formed by the adjoining tops of two fingers diminishes. It’s also helpful to measure the phalangeal depth ratio, where the ratio of the thickness of the end of the finger to the middle part of the finger plays a decisive role.
In addition to digital clubbing, other possible changes related to PHO include changes in your skin and bones. Skin changes often involve the thickening of the skin (dermal hypertrophy), leading to thicker features on your face and increased creasing of your scalp skin; a condition known as cutis verticis gyrata. You may also experience non-pitting, round swellings on both legs, resembling “elephant legs”. Areas where muscles do not adequately cover, such as ankles and wrists, may show a noticeable thickening.
Excessive growth of the skin glands may result in conditions like seborrhoea, a type of skin rash, exaggerated sagging of the eyelid (blepharoptosis), acne, and excessive sweating (hyperhidrosis).
Periostosis (excessive bone growth) may either have no symptoms, or may be recognized by tenderness when touching the affected area. Joint effusions (fluid build-up in the joints) can be noticed in larger joints like the knees and wrists. It may be more difficult to ascertain this in smaller joints due to the surrounding tissue swelling.
Testing for Hypertrophic Osteoarthropathy
There aren’t any blood tests that can conclusively diagnose Primary Hypertrophic Osteoarthropathy (PHO). However, several physical signs might suggest this condition. These can include changes to the fingers like thickening or a bulbous shape at the tips of the fingers, known as clubbing. Other signs are changes in facial features and swelling of the legs. These symptoms alongside the enlargement and thickening of tubular bones, such as the long bones in your arms and legs, might lead a doctor to suspect PHO.
However, doctors also need to check for other conditions that might cause similar symptoms. Particularly, lung cancer is crucial to rule out, as PHO is often indirectly caused by this cancer. A chest X-ray can be done to check for abnormalities inside the chest, particularly if clubbing only appears in one hand. If clubbing only appears on one side, the cause might be related to blood vessels or nerves; in that case, a test called angiography can potentially reveal the root cause.
Fluid from joint spaces in these cases is known to be thick and tends to clot, with no signs of inflammation when viewed under a microscope. X-rays of arms and legs often show unusual tissue and bone structures, even if the person doesn’t feel any symptoms. Long-standing cases of clubbing can lead to ‘acro-osteolysis’, a condition where bones of the fingers dissolve, or the formation of additional bone at the fingertip. Another common occurrence is the formation of new layers of bone beneath the outer lining of bone and in the long bones of the forearms and legs. Sometimes, new bone formation can also involve ligaments and the fibrous tissue in between bones.
In the early stages of the disease, a radionuclide bone scan may demonstrate changes in the bone that can suggest PHO. However, the changes seen in the bone scan are not only seen in PHO and could also indicate other conditions wherein such bone changes occur. A combination of CT scans and a special scan known as F-fluorodeoxyglucose positron emission tomography (FDG-PET) may show signs of bone and tissue inflammation and suspect areas of high metabolism in the body’s organs. This information could indicate potential causes if the PHO is secondary to another condition.
Treatment Options for Hypertrophic Osteoarthropathy
Secondary hypertrophic osteoarthropathy is a condition that results from an underlying disease. So, the best way to treat this condition is to address the root cause. For instance, people have seen improvements after removing lung tumors, fixing heart defects from birth, or treating heart infections. There also have been recoveries in patients with cystic fibrosis after receiving a lung transplant.
However, if doctors can’t find any underlying cause and determine that the clubbing (a symptom where fingers and toes become wider and rounder) is the primary condition, treatment can begin to control the symptoms. Cyclooxygenase-2 inhibitors, which are drugs that stop an enzyme involved in inflammation, are the first choice. These medications help because they block the overproduction of PGE2, a substance that leads to more VEGF, a type of protein that stimulates the formation of blood vessels.
In cases where the bone pain is hard to control, bisphosphonates, which help control the amount of calcium in the bone and reduce bone pain, can be particularly useful. For patients with hypertrophic osteoarthropathy (an enlargement of the fingers/toes or other bones) due to cyanotic congenital heart disease (a heart disease present from birth that leads to a lack of oxygen) or lung cancer, octreotide, a medication that copies a natural hormone in your body and can help with pain, has been useful.
What else can Hypertrophic Osteoarthropathy be?
The condition known as ‘clubbing’ usually suggests that a patient could have a disease called hypertrophic osteoarthropathy. It’s crucial to distinguish this from ‘pseudo-clubbing’, seen in conditions like secondary hyperparathyroidism (common in chronic kidney disease), scleroderma, and sarcoidosis. In pseudo-clubbing, the angle between the nail plate and the fold of skin at the base of the nail is less than 180 degrees, while in regular clubbing, this angle is more than 180 degrees. Also, pseudo-clubbing may not be symmetrical, but clubbing usually is. People with pseudo-clubbing usually show signs of acro-osteolysis in X-rays, while those with clubbing show overgrowth of the bones at the tips of the fingers. Although, there might be overlap in these observations between both conditions.
Notably, skin changes like coarse, thickened skin might hint at another condition called acromegaly. Other signs of acromegaly include teeth that project forward, changes in the size of the pituitary gland seen in X-rays, and increased growth hormone levels. Thyroid acropachy could also cause clubbing and swelling in the digits with bone overgrowth, and is often connected to skin changes caused by thyroid disease—this can be easily mistaken for hypertrophic osteoarthropathy.
Another condition, named POEMS syndrome, may display signs of clubbing, excessive sweating, and skin thickening. Intriguingly, those with POEMS syndrome and hypertrophic osteoarthropathy usually have high levels of a substance in the blood known as VEGF. Certain changes in the membrane covering the surface of bones may occur in cases of trauma, various types of bone infections, conditions resulting from too much vitamin A or fluoride, leukemia, types of juvenile arthritis, bone tumors, and sickle cell disease. There have also been reports of bumpy bone inflammation caused by a medicine called voriconazole in patients who have had kidney transplants. These conditions should all be thought of when considering the diagnosis of hypertrophic osteoarthropathy.
In short, diagnosing hypertrophic osteoarthropathy often involves eliminating other possible causes, especially lung cancer, in all patients showing signs of the disease.
What to expect with Hypertrophic Osteoarthropathy
PHO, a type of medical condition, generally resolves on its own during adolescence without any need for treatment. On the other hand, SHO, another related condition, depends on the underlying disease that’s causing it. It’s been found to have worse outcomes in people who are suffering from diseases like cystic fibrosis, tuberculosis, idiopathic pulmonary fibrosis (a type of lung disease with unknown causes), extrinsic allergic alveolitis (a lung disorder resulting from an allergic reaction to inhaled substances), and asbestosis (a lung disease caused by inhalation of asbestos particles).
When it comes to cancer, there hasn’t been any research into how SHO affects the prognosis, or expected course and outcome of the disease.
Possible Complications When Diagnosed with Hypertrophic Osteoarthropathy
The problems associated with hypertrophic osteoarthropathy, a bone disease, mainly include pain and a decreased ability to move the affected body part. This happens due to swelling and inflammation of the area around the bone.
Complications of Hypertrophic Osteoarthropathy:
- Pain
- Loss of motion range due to swelling
- Inflammation around the bone (periostitis)
Preventing Hypertrophic Osteoarthropathy
If you’re getting checked for a condition called hypertrophic osteoarthropathy, you should be ready to provide a lot of information about your past health and your family’s health history. Hypertrophic osteoarthropathy is a medical term for a condition that typically causes swelling of the skin and bones, mostly in the arms or legs.
While practicing a healthy lifestyle is always beneficial for overall health, there are currently no confirmed ways to specifically prevent this disease. Your doctors and nurses will help you understand more about your situation and answer any questions you have.
