Idiopathic calcinosis cutis of the penis.

Calcification of the skin occurs in four main forms namely dystrophic, metastatic, iatrogenic and idiopathic. Idiopathic calcinosis cutis of the penis is exceedingly rare as only five cases have been reported till date to the best of our knowledge. Herein, we present another case of this rare entity in a 29-year old man and discuss its probable pathogenic origin.

INTRODUCTION

The term ′calcinosis cutis′ refers to the deposits of calcium in the skin. Two main forms, with different pathogenic mechanisms, are usually identified.[1] In the metastatic form, the patient has abnormal serum levels of calcium, phosphorus or both. In the dystrophic form, calcium and phosphorus levels are normal, and there is a local condition that predisposes to calcinosis. The term ‘idiopathic calcinosis’ is used when neither local tissue injury nor systemic metabolic disorder can be demonstrated. We present a case of idiopathic calcinosis cutis of the penis.

CASE REPORT

A 29-year old man presented with an 11-month history of a solitary asymptomatic firm mass on the penile skin. He had no systemic symptoms. There was no history of either trauma to the penis, or of any inflammatory process/growth in the penile skin. Clinical examination showed a flat, hard plaque, 1 cm in diameter, covered by normal skin on the shaft of the penis [Figure 1]. The rest of the physical examination revealed no abnormality. Renal function tests, serum calcium and phosphorus, and parathyroid hormone level, were within normal limits. The lesion was excised under local anesthesia [Figure 2]. On histological examination, the epidermis was normal and no cysts were present. The dermis was widely infiltrated by deposits of calcific material, which stained black with von Kossa's stain [Figure 3]. Surrounding these deposits fibrous tissue and foreign body giant cells were visualised [Figure 4]. Immunohistochemical study for cytokeratin did not show any keratin around the calcium deposits. There were no adnexal structures in any of the examined sections. Healing was satisfactory and, 3 months later, no new calcified deposits could be detected.

Figure 1

Flat, hard nodule, 1 cm in diameter, covered by normal skin on the shaft of the penis

Figure 2

Flat nodular lesion excised under local anesthesia

Figure 3

Dermal deposits stained black with von Kossa's stain

Figure 4

Histology of excised nodule shows deposits of calcific material, surrounded by fibrous tissue (H&E)

DISCUSSION

Calcinosis cutis is a term used to describe a group of disorders in which calcium deposits form in the skin. Firm, multiple, whitish dermal papules, nodules or subcutaneous nodules are commonly found. Of the various classifications, the commonly used classification divides calcinosis cutis into four groups: dystrophic (commonest), metastatic, iatrogenic and idiopathic (rarest). A few rare types have been variably classified as dystrophic or idiopathic. These include calcinosis cutis circumscripta, calcinosis cutis universalis, tumoral calcinosis and transplant-associated calcinosis cutis. Dystrophic calcinosis includes those conditions in which calcification occur in the damaged tissue. Various conditions including connective tissue disease, infection, inflammatory processes, chronic venous stasis, cutaneous neoplasms and trauma can cause dystrophic calcinosis which may be localized (calcinosis circumscripta) or widespread (calcinosis universalis).[1] Metastatic calcification due to deposition of calcium resulting from elevated serum levels of calcium or phosphorus is most commonly associated with renal failure.[1] Metastatic calcinosis of the penis has been observed in a series of patients with end-stage renal failure and secondary hyperparathyroidism.[2] Iatrogenic and traumatic calcinosis is associated with medical procedures or occupational exposures that may involve both tissue damage and local elevated calcium concentrations. Idiopathic forms of calcification like idiopathic scrotal calcinosis, subepidermal calcified nodule and tumoral calcinosis are forms of cutaneous calcification of unknown cause with normal serum calcium.[1]

The pathogenesis of calcinosis cutis is not completely understood. Metabolic and physical factors are pivotal in their development. Ectopic calcification can occur in the setting of hypercalcemia and/or hyperphosphatemia without preceding tissue damage by calcium-phosphate nucleation, and crystalline precipitation. Alternatively, damaged tissue may allow an influx of calcium ions leading to subsequent crystalline precipitation. Tissue damage also may result in denatured proteins that preferentially bind phosphate. Calcium then reacts with bound phosphate ions leading to precipitation of calcium phosphate

In our case, no pre-existing lesion or predisposing cause of calcification could be identified. To our knowledge, similar clinical and histological aspects have been observed in only a few cases.[3-5] All these cases presented with one or two nodules on the skin of the penis, with almost similar average duration (mean 9.8 months; range 6-10 months), between 4 and 20 mm in diameter (mean: 12.25 mm), in young people (mean and median ages were 18.8 and 16 years, respectively; range 13-25 years), with no history of local or systemic favouring factors, and without evidence of epithelial cyst lining or an adnexal tumor even with immunohistochemical studies.[4] The pathogenesis of idiopathic penile calcification may be similar to that proposed for idiopathic scrotal calcinosis, a more common disease characterized by multiple calcific deposits within scrotal skin.[6] The principal debate concerning the cause of this condition is whether the calcium is deposited at the site of epidermal cysts or whether the calcified nodules are truly idiopathic. Several authors have suggested that scrotal calcinosis is the result of changes in pre-existing epidermal cysts. The keratinous contents of such cysts become inspissated and undergo dystrophic calcification that results in attenuation and resorption of the cyst walls.[6] However, Wright et al.[7] failed to show positive staining with antikeratin antibodies in multiple sections of 63 lesions in nine patients with scrotal calcinosis, which makes the proposal that all traces of keratin could have been removed from the site of the lesion, in all the slides that were examined, quite untenable. In our case also, microscopic studies and immunohistochemical staining for keratin have shown no evidence of keratin in the dermal tissue immediately adjacent to the calcium deposits.