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An unusual cause of a discharging sinus

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Q1: What is the diagnosis?

Calcinosis cutis.

Calcinosis cutis is characterised by the deposition of calcium salts in the subcutaneous tissues of the body. Metastatic calcifications can occur in the body in hyperparathyroidism and end stage renal disease.1 Calcifications can also occur in a variety of other clinical settings. The lesion can present as a mass and is amenable to FNAC.2 In cytological preparations, deposits of calcium salts can be both amorphous and refractile on Diff-Quik and Papanicolaou stain. However, the material may not be birefringent with these stains. Alizarin red S stain for calcium permits demonstration of the characteristic birefringence.2

A group of extremely small bacteria capable of precipitating calcium salts implicated in the pathogenesis of urinary calculi and calcific atherosclerosis have been identified as the nanobacteria. The pathogenesis of calcinosis cutis and its significance in conjunction with a variety of unrelated scarring and pre-existing cutaneous entities are incompletely understood. In a series of cases, including basal cell carcinoma with dystrophic calcification, subepidermal calcified nodule, pilomatricoma, and tumoral calcinosis, Morgan ultrastructurally examined the presence of Nanobacteria sp.3 All cases were negative for nanobacteria. Dystrophic calcification that occurs in conjunction with these entities does not likely involve a bacterial-induced aetiology. The cause of these entities remains unknown.

Subepidermal calcified nodule is a form of calcinosis cutis that most commonly occurs in children. The typical clinical presentation is of a solitary verrucous nodule on the face, but occasionally multiple lesions may be seen.4

Smears usually show amorphous granular material consistent with calcium, and occasional histiocytes. The presence of amorphous calcium salts along with histiocytes in the appropriate clinical setting is diagnostic of calcinosis cutis.1 The diagnosis can be confirmed on histology.

Although this benign lesion can be suspected on radiological and clinical examination, FNAC and biopsy should always be done to rule out calcification in other potentially tumorous conditions. Metastasis of this disorder has also been reported, though it is still benign.

Localised lesions can be injected with intralesional corticosteroids that may be beneficial due to the anti-inflammatory effect and inhibitory effect on fibroblast activity. Probenecid and colchicine have been beneficial in some individuals. In patients with hyperphosphataemia, magnesium or aluminium antacids may be effective due to phosphate binding ability. However, use in patients with renal insufficiency may result in magnesium or aluminum toxicity. Sodium etidronate and diphosphonates may reduce bone turnover and inhibit the growth of ectopic hydroxyapatite crystals. However, prolonged treatment is necessary, and paradoxical hyperphosphataemia may result. There have been variably beneficial effects with the use of the calcium channel blocker diltiazem.5,6 The therapeutic effect of this is believed to be the antagonism of the calcium-sodium ion pump. Surgical excision can be undertaken when there is pain, recurrent infection, ulceration, or functional impairment, though surgical trauma can stimulate calcification and recurrence is not uncommon.

Learning points

  • Not every discharging sinus is due to infection or malignancy.

  • Not all that appears radio-opaque on radiographs is solid.

  • Examination of hands can provide crucial diagnostic clues even for the lesions in the lower extremity.

  • Calcinosis cutis, although more commonly associated with the CREST syndrome, can present as an isolated lesion.

  • As in this case, calcinosis can be present without any renal or other systemic disease.

Q2: What other features can be associated with the present clinicoradiological picture?

Raynaud’s phenomenon, oesophageal dysmotility, sclerodactyly, and telangiectasia combine with calcinosis to form the CREST syndrome.

Q3: Which immunological test is positive in a majority of patients with this clinical condition?

Anticentromere antibodies are seen in a very high proportion of patients with CREST syndrome.

Final diagnosis

Calcinosis cutis.

References

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