Congenital calcinosis cutis of the foot.

Calcinosis cutis is a rare disease characterized by deposition of insoluble calcium salts in the skin. Subepidermal calcified nodule is a form of idiopathic calcinosis cutis that commonly affects children but rarely presents at birth. Herein we describe a healthy 10-month-old boy who had a solitary hard nodule on the left foot since birth. Surgical excision of the nodule was done and histopathology confirmed the diagnosis of subepidermal calcified nodule.

Introduction

Calcinosis cutis is a group of disorders characterized by the presence of calcium deposits in the skin. There are four forms of calcinosis cutis: metastatic, dystrophic, iatrogenic, and idiopathic.[1] Metastatic calcification occurs in normal tissues secondary to abnormal calcium and phosphate metabolism. The dystrophic type of calcinosis cutis, the commonest form, manifests secondary to tissue damage. The iatrogenic type occurs following treatment. In the idiopathic type, calcinosis presents in the absence of either tissue damage or abnormal mineral metabolism. Idiopathic scrotal calcinosis, tumoral calcinosis, and subepidermal calcified nodule are grouped under idiopathic calcinosis. We present a case of congenital subepidermal nodule.

Case Report

A 10-month-old boy was brought to our department for an asymptomatic solitary, 3-mm size, firm white nodule over the heel of the left foot that had been present since birth [Figure 1]. The nodule had slowly grown in size during the first few months of life and then remained static. There was no discharge from the nodule. The infant had been delivered normally. The family history and medical history were unremarkable. General and systemic examination was normal. The infant had normal serum mineral values and renal function tests.

Figure 1

Photograph showing a single white nodule over heel of left foot

The nodule was excised and sent for histopathological study. Microscopic examination revealed massive compact hyperkeratosis and acanthosis of the epidermis. Dark basophilic-stained granular calcium deposits were found within cystic spaces in the dermis [Figure 2]. Von Kossa stain confirmed the presence of calcium [Figure 3]. Based on the clinical features and histopathology, we arrived at a diagnosis of subepidermal calcified nodule. On follow-up there has been no recurrence.

Figure 2

Photomicrograph shows massive compact hyperkeratosis, acanthosis and basophilic calcium granules within cystic spaces (H & E × 200).

Figure 3

Photomicrograph showing calcium granules that have taken up black color (vonKossa × 200).

Discussion

Solitary congenital nodular calcification was first described by Winer in 1952.[2] There are only a few case reports of subepidermal calcified nodule from India. Subepidermal calcified nodule, also called cutaneous calculi, predominantly affects children, and in some cases it is present at birth.[2-4] It is extremely rare in adults. Males are more commonly affected than females.[1] The majority of cases of subepidermal calcified nodule present as an asymptomatic small solitary nodule. Occasionally, there may be a few to numerous nodules.[3] Congenital calcinosis may also occur in a bilateral distribution. There may be a surrounding erythematous halo. Lesions are often present over the ears, eyelids, nose, fingers, and feet.[245] Occasionally, there may be involvement of the mucosa of lip, gingiva, hard palate, and tongue.[6] The surface can be smooth or warty. Younger lesions may have surface ulceration, whereas older lesions can be warty.[7] These nodules are not associated with systemic or cutaneous disorders. Subepidermal nodule can be considered as one of the differential diagnosis for wart or molluscum contagiosum in children.

The etiology remains uncertain. These lesions do not appear to arise from sweat glands or a preexisting nevus. It is hypothesized that subepidermal calcified nodule represents dystrophic calcification following needle stick injury during the neonatal period.[8] Some authors speculate that congenital calcinosis could be induced by trauma during gestation.[4]

Histopathological examination shows calcium deposits predominantly in the upper dermis, though in large nodules they may be seen in deeper dermis.[2] Calcium is present as closely aggregated globules. Occasionally, there are few foreign body giant cells around the deposits. Calcium granules may be found within the epidermis, indicating transepidermal elimination.

The treatment of choice is surgical excision. If small and multiple, electrodessication or CO2 laser ablation may be done.[9] Recurrence following surgical excision is uncommon.[10]

This case is reported because of the rarity of congenital calcinosis cutis, especially that involving the foot.