Chondrodermatitis Nodularis

Synonyms: CDN, Chondrodermatitis nodularis helicis (CNH) (or antihelicis – depending on site of lesion), chondrodermatitis nodularis chronica helicis (CNCH), ear pressure sore, painful nodule of the ear.

The unambiguous term painful nodule of the ear is increasingly preferred to describe this benign but somewhat troublesome condition. It is thought to be due mainly to the effect of pressure on the blood supply of the cartilage and skin of the external auditory apparatus. Inflammation in the skin, associated oedema, trauma, cold, or sun-related injury are all thought to be possible contributory factors.¹ Damage and necrosis affects the cartilage and overlying skin; the lesion is slow to heal as vessels from the skin must penetrate through to serve the auricular perichondrium and are easily compromised. The right ear is most commonly affected, presumably as a majority of people sleep habitually on that side. It can cause significant discomfort and be a chronic problem that may need surgical intervention.

There are no reliable figures for its incidence or prevalence but it is undoubtedly a relatively common condition in ENT clinics (where one study found it to be the commonest condition affecting the external ear)¹, and in primary care.

Risk factors

It is commonest in older men with white, sun-damaged skin, but can affect people of all ages, gender and pigmentation. M:F ratio is roughly 2:1. The use of apparatus that puts pressure on the external ear such as headphones may precipitate the condition, as may a tendency to always sleep on the same side.

Symptoms

Classically the patient notices a sudden onset of a painful nodule on the external ear. The nodule usually sits on the helix (commonly at its apex), but may also affect the antihelix. Most patients recognise that they habitually sleep with the weight of their head resting on the affected ear. There may be recurrent bouts of pain in the nodule that can be precipitated by pressure, trauma or cold; these may be short-lived or persist for up to an hour. The nodule usually grows for a few months and then remains static in size.

Signs

The nodule is firm on palpation and tender to touch and usually from 0.5–2 cm in diameter. It is well circumscribed and round or oval with a raised, rolled edge and overlying actinic skin; there may be a central plug of necrotic skin and collagen. If the plug is removed then a small central channel may be found underneath. There can be slight redness at the edge of the lesion. The lesion is usually single but multiple and bilateral variants do exist. There should not be any associated regional lymphadenopathy unless there is superadded infection of the lesion; regional nodes should be checked as skin malignancy is one of the condition's major differential diagnoses.

• Basal cell carcinoma
• Keratoacanthoma
• Actinic keratosis
• Squamous cell carcinoma
• Malignant melanoma
• Idiopathic cystic chondromalacia
• Relapsing polychondritis
• Fibroxanthoma

If the diagnosis is clear from the history and examination then there may be no need to investigate further. Since its major differential diagnoses are potentially dangerous, it is prudent to biopsy the lesion if there is any doubt as to its nature. A shave-biopsy will show central necrotic epidermis with oedematous epidermis at the periphery with acanthosis. There is nodular degeneration of collagen surrounded by vascular granulation tissue that may be infiltrated by lymphocytes.

The condition is benign and traditionally not thought to be related to any systemic illness,¹ but a recent series shows an association with immune-mediated vascular compromise and necrobiotic collagenous disease such as granuloma annulare, especially in younger patients.²

The lesion rarely resolves spontaneously and so will usually need some form of treatment if it is causing discomfort or annoyance.

Conservative management

Reduction of sun or cold exposure may be beneficial, if they are thought to be relevant precipitating or maintaining factors. Home-made pressure-relieving devices that are worn whilst sleeping have been shown to be beneficial and curative in some cases.³ They are usually made of a small piece of foam or sponge held in place by a headband. Traditionally the response rate has been thought to be low and many have advocated immediate surgical excision. However, a recent study found that around 80% of conservatively treated patients were healed at one month, compared to a recurrence rate of about a third in those treated surgically. The authors of this study advocate a trial of conservative therapy in all patients.³

Surgical management

There are a range of surgical techniques used to achieve excision of the affected cartilage with reconstruction of the overlying skin. Cryotherapy and laser ablation have also been used. Excision of the damaged area of cartilage is usually successful but recurrence is known to occur at the edge of the excised area. A technique of narrow elliptical excision of the skin lesion with shaving of the underlying cartilage appears to be as effective, less invasive and to have similar recurrence rates (around 13.5% after 4 years or so).⁴ Lesions on the antihelix seem to be more likely to recur after excision than those on the helix.⁴

The prognosis is excellent with the lesion usually progressing no further, or responding to conservative or surgical treatment. In the minority of patients who have recurrence then further surgical or conservative treatment may be successful.