Answer

Tuberous xanthoma of scalp.

Discussion

Xanthomas occur as a result of tumor-like deposits of lipids in different tissues, most notably skin, tendon and eyes. These disorders may occur as a result of inherited genetic defects of lipid homeostasis (most common cause), systemic diseases (such as hypothyroidism and renal failure) and certain medications (e.g., systemic retinoids). There are several varieties of xanthomas viz. tendon xanthoma, xanthelasma palpebrarum (most common), tuberous xanthoma, palmar xanthoma, eruptive xanthoma, planar xanthoma, tubo-eruptive xanthoma, verruciform xanthoma, nodular xanthoma and diffuse plane xanthoma. ^[1] Tuberous xanthoma (our case) is characterized by the occurrence of small to exuberant exophytic, yellowish or orange papulo-nodular lesions, located over the extensor aspect of elbows, knees and heels. ^[2] However, they may occasionally occur on the face, knuckles, toe joints, axillary and inguinal folds and buttocks. ^[1] Other uncommon sites have rarely been reported for other varieties of xanthomas viz. eyelids (xanthoma disseminatum), ^[3] earlobe (verruciform xanthoma) ^[4] and scalp (verruciform xanthoma). ^[5] In our case, tuberous xanthoma occurred on the scalp; this association has not yet been reported in the English literature.

Xanthomas are commonly associated with underlying primary or secondary dyslipidemia, thus often acting as risk factors for coronary artery heart disease or pancreatitis. However, verruciform xanthoma and xanthoma disseminatum may occur in normolipemic patients; the latter variety being often associated with other disorders such as paraproteinemias, systemic lupus erythematosus (SLE) and lymphoma. ^[2] Tuberous xanthomas are commonly associated with type III (mixed) Frederickson hyperlipoproteinemia, ^[2] and also with type IIa, type IIb and other secondary hyperlipoproteinemias (e.g., biliary cirrhosis, etc.). Rarely, it may occur in normolipemic patients; ^[6],[7],[8] however, there may be associated underlying systemic disorders or malignancy. ^[6] Association with pityriasis rubra pilaris has also been reported. ^[9] In our case, the patient showed normal lipid metabolism status and absence of any other systemic disorder or malignancy.

The diagnosis of xanthoma can be confirmed histologically; however, the type is suggested by the clinical appearance. The hallmark histopathological feature is the presence of vacuolated macrophages in the dermis, which actually contain lipid droplets (foam cells); Touton giant cells may also be present. Occasionally tuberous xanthoma may show fibrosis and sporadic cholesterol clefts. Similar HP features were found in our patient also. This condition responds effectively to the treatment of underlying dyslipidemia. As the lesions are localized in our case (scalp) and the patient is normolipemic, carbon dioxide laser ablation of the lesions has been planned.

In our case, tuberous xanthoma is localized to the scalp; this happens to be the first English report of such an unusual location. Also, the occurrence of this type of xanthoma in a normolipemic patient with no other systemic or neoplastic disorder has rarely been reported. The patient has been referred to the Department of Plastic Surgery for management of the lesions and we are also evaluating the role of carbon dioxide laser ablation of the large lesions.