2. Multiple Depigmented Macules on Trunk

Pawan Kumar¹

(1)

Kempegowda Institute of Medical Sciences, Bengaluru, India

Pawan Kumar

Keywords

Idiopathic guttate hypomelanosisBenign leukodermaGeriatricSenile degeneration

A 55 year old male presents with multiple hypopigmented macules over back and abdomen since 1 year. They are asymptomatic and there is no increase in size after onset but they are increasing in number. No other family member is affected. On examination he had multiple small round or angular hypo- and depigmented smooth surfaced macules of size ranging from 1 to 5 mm over abdomen and back (Fig. 2.1). Palm and sole are normal. Based on this clinical information and photograph what is the diagnosis?

(a)

Hyperkeratotic confetti leukoderma
(b)

Vitiligo
(c)

Idiopathic guttate hypomelanosis
(d)

Cole’s disease

../images/471276_1_En_2_Chapter/471276_1_En_2_Fig1_HTML.jpg — Figure 2.1

Multiple depigmented sharply demarcated macule on abdomen and back. (Courtesy: Dr. Piyush Kumar)

Dermoscopy of largest lesion revealed amoeboid pattern with pseudopod like projections (Fig. 2.2).

../images/471276_1_En_2_Chapter/471276_1_En_2_Fig2_HTML.jpg — Figure 2.2

Dermoscopy image showing amoeboid pattern with pseudopod like projections. (Courtesy: Dr. Piyush Kumar)

Diagnosis

Idiopathic guttate hypomelanosis

Discussion

Idiopathic guttate hypomelanosis (IGH) is a common, acquired and benign dermatosis. The incidence of IGH is associated with advancing age. Although it affects nearly 87% of the population aged more than 40 years, it may also be seen in young adults into the 20s and 30s. Some studies report a female predilection. It is more frequent in fair-skinned people.

Pathogenesis of IGH is not well known. Ageing, chronic sun exposure, genetics, trauma, autoimmunity, and local inhibition of melanogenesis have been proposed as causative factors [1]. Sunlight has been long incriminated in the pathogenesis of IGH because lesions are mainly located at sun exposed body areas, as evidenced by occurrence of IGH lesions in patients receiving PUVA/NB-UVB treatments. Repeated trauma plays a role. High incidence of lesions on the anterior surface of tibias, where subcutaneous tissue is less, and in persons using body scrubs clearly shows that the successional irritation of vulnerable body parts may essentially contribute to the formation of IGH lesions.

Clinically IGH is characterized by multiple, small, scattered, discrete, round or oval, porcelain-white macules ranging in size from 0.2 to 2 cm. They are smooth but occasionally scaling may be present. Skin markings are reduced within lesion. The macules are usually seen in upper and lower extremities, trunk and face. The number increases with time but size remains same. There is no spontaneous repigmentation. Usually they are asymptomatic even though some mention mild itching.

Diagnosis is usually made on clinical grounds. The main histopathological findings observed in IGH lesions are basket weave hyperkeratosis, patchy absence or decreased number of melanocytes and flat rete-ridges [2]. Melanocytes may have less melanosomes, dilatated endoplasmic reticulum, swelled mitochondria and attenuated dendrites. Melanosomes contained in the adjacent keratinocytes may be reduced or even absent. Dermoscopy shows normally pigmented specks scattered within the macules and perimetric pigmentary extensions. IGH may be developed according to four patterns, which are nebuloid, petaloid, amoeboid and feathery. Dermoscopy can be a valuable tool in the evaluation of lesions of IGH [3]. IGH can assume varying morphologies on dermoscopy:

Amoeboid: most common presentation, pseudopod-like extensions
Feathery: irregularly pigmented with feathery margins and whitish central area
Petaloid: polycyclic margins, resembling petals of a flower
Nebuloid: indistinct, smudged borders. More often in early lesions.