What Is Calcinosis Cutis?
Calcinosis cutis is a condition in which abnormal deposits of calcium salts form within the skin. It is not a primary skin disease but rather a consequence of underlying metabolic disturbance — most commonly, chronically elevated cortisol levels. In dogs, this most often occurs either as a result of hyperadrenocorticism (Cushing's disease) or, significantly, as a side effect of prolonged or high-dose corticosteroid therapy. The skin becomes firm, gritty, chalky, and frequently inflamed as the body attempts to deal with insoluble mineral deposits where they should not exist.
Whilst calcinosis cutis can resolve with appropriate management of the underlying cause, it is a slow process that demands patience from both owners and clinicians. In some cases, the deposits cause chronic discomfort, secondary infection, and considerable disfigurement before resolution is achieved.
Why Steroid Use Causes This Problem
Glucocorticoids — whether produced endogenously in Cushing's disease or administered therapeutically — affect tissue calcification through several mechanisms. Elevated cortisol impairs the skin's ability to regulate cellular calcium metabolism. It induces structural changes in collagen, creating an abnormal matrix that is prone to mineralisation. It also affects kidney handling of phosphate and influences vitamin D metabolism, further disrupting the balance of calcium in tissues.
The risk is greatest with long-acting injectable corticosteroids, high-dose oral preparations used over extended periods, and potent topical steroids applied to large body surface areas. Dogs receiving steroids for the management of atopic dermatitis, immune-mediated diseases, or inflammatory conditions are the most commonly affected population. Not every dog on steroids will develop calcinosis cutis, and individual susceptibility appears to vary, but the risk increases substantially with duration and cumulative dose.
Where Lesions Appear
Calcinosis cutis in dogs has characteristic distribution patterns. The dorsal midline — running from the neck down the back — is the most commonly affected area, presenting as firm, raised plaques that may be white or yellowish in colour and feel almost sandy or chalky when palpated. The ventral abdomen, groin, and axillae (armpits) are also frequently involved. Lesions in the groin area can be particularly uncomfortable, causing dogs to scoot or show signs of pain on movement.
The skin overlying the deposits is often inflamed, and ulceration is not uncommon as the calcium deposits erode through the surface. Secondary bacterial and yeast infection frequently complicates the picture, as the disrupted skin barrier provides easy entry for opportunistic organisms. The associated odour and discharge can be distressing for owners and uncomfortable for the dog.
Recognising the Signs
Early calcinosis cutis may be subtle — mild scaling, slight thickening of the skin, or small firm nodules that owners may initially attribute to other causes. As deposits enlarge, the characteristic chalky, gritty texture becomes more apparent to the touch. Affected skin may crack, ooze, or bleed. Dogs often lick at lesions, and pruritus can be significant, particularly when secondary infection develops.
In dogs with underlying Cushing's disease, calcinosis cutis is almost always accompanied by other signs: a pot-bellied appearance, increased thirst and urination, muscle wasting, alopecia, and thin, fragile skin. Dogs receiving exogenous steroids may show similar signs collectively referred to as iatrogenic Cushing's syndrome. Recognising this constellation of signs helps direct the diagnostic workup.
Diagnosis
Physical examination often raises strong suspicion, and histopathology of a biopsy sample confirms the diagnosis by demonstrating calcium deposits within the dermis. Von Kossa staining or Alizarin Red staining are used to visualise the mineral deposits in tissue sections. Radiographs may reveal the calcification in severe cases, though this is typically not required for diagnosis.
Confirming or excluding underlying hyperadrenocorticism is essential. A low-dose dexamethasone suppression test or ACTH stimulation test is used to diagnose Cushing's disease. Blood biochemistry often shows elevated alkaline phosphatase in affected dogs, though this finding is not specific. Abdominal ultrasound to assess adrenal gland size and morphology forms part of the workup for suspected Cushing's disease.
Treatment and Management
Addressing the Underlying Cause
Where calcinosis cutis has developed due to steroid administration, gradual tapering and discontinuation of the corticosteroid is the primary intervention where the underlying disease allows this. Alternative immunosuppressive agents such as ciclosporin, oclacitinib, or other targeted therapies may be substituted to manage the original condition without the same mineralisation risk. The deposits often begin to resolve over months once cortisol excess is corrected, though resolution is rarely rapid.
In dogs with Cushing's disease, treatment with trilostane or mitotane to lower cortisol production is the mainstay of management. Successful control of Cushing's disease typically leads to gradual resorption of calcinosis cutis deposits over a period of months to years.
Local Wound Care
Secondary infection management is important for dog comfort and to prevent worsening of the primary lesion. Antimicrobial shampoos with chlorhexidine help reduce bacterial and yeast colonisation. Where ulceration or discharge is present, gentle cleansing and appropriate antimicrobial therapy — topical or systemic depending on severity — are indicated. Soaking affected areas in dilute aluminium acetate solution may help manage seropurulent discharge.
Some clinicians have explored the use of dimethyl sulphoxide (DMSO) gels applied topically to facilitate calcium resorption, though evidence for this approach remains limited. Chelating agents have been used experimentally but are not part of routine practice.
Prognosis and Timeframe
Calcinosis cutis is slow to resolve even under ideal treatment conditions. Owners should be counselled to expect a timeline of six months to two years for significant improvement, and some dogs retain evidence of previous deposits indefinitely. The prognosis is best in dogs where a clear inciting cause is identified and successfully managed, particularly those in whom steroid therapy can be discontinued or substantially reduced.
Lesions that persist despite adequate management of the underlying cause, or those causing unacceptable discomfort, may occasionally be considered for surgical debridement — though surgery in areas of mineralised, fragile skin carries its own risks and is generally approached cautiously. Most clinicians prefer patience and conservative management as the first approach.