Clinico epidemiological study of pityriasis alba

Introduction

Pityriasis alba is a relatively common skin disorder characterized by the presence of asymptomatic superficial hypopigmented macules with slight overlying scaling, located usually on the face, neck and shoulders. Although this condition is frequently encountered in dermatological practice, only a few studies are available on the subject. In view of this, a study was carried out to analyse the clinical spectrum and epidemiologic characteristics of pityriasis alba and to elucidate the role of various suggested aetiologic factors in pityriasis alba.

Materials and Methods

Two hundred patients with pityriasis alba, attending the outpatient department of Command Hospital, Bangalore within the period of February ′96 to March ′97 were included in the study. Diagnosis of pityriasis alba was made according to Francisco Vargas-Ocampo clinical description of the condition. [1] A detailed history was taken with particular stress to personal and family history of atopy, climatic variations, nutritional status and any topical application. Clinical examination was made and findings were recorded.

Routine haematological and urine examination were carried out in all cases. Stool was examined for the presence of ova or cyst. Scarping for fungus and gram stain from the lesions were done in most of the cases. Scraping material was sent for the culture of fungus and bacteria, whenever necessary. Biopsy and histopothological examination were carried out in a few patients with long standing lesions.

Results

The age group of the patients studied, ranged from 8 months to 32 years, with majority of the patients below 15 years [Table - 1]. The study group comprised of 115 (57.5%) males and 85 (42.5%) females. The male to female ratio was 1.35:1.

The duration of the lesions, at the rime of presentation varied from less than 1 month to more than 1 year, with majority of the patients having complaints of less than 6 months duration (84.5%). Only a few patients had lesions of more than 1 year.

A history of increased itching on exposure to sunlight was obtained from 17 (8.5%) patients. Exacerbation of the lesions during winter was observed in 78 (39%) patients, whereas 5 had summer exacerbation. No seasonal exacerbation was observed in the remaining 127 (63.5%) patients.

A personal history of atopy in the form of allergic rhinitis, asthma or atopic dermatitis was present in 34 (17%) patients and family history of atopy was elicitable from 68. 5% of patients. Past history of worm infestation was present in 91 (45.5%) patients.

Dermatological examination revealed hypopigmented macules in 193 (96.5%) cases and

hypopigmented macules with central hyperpig-mentation in 7 cases. No history of any topical application was present in these cases. Number of lesions varied greatly among patients, with majority of patients having 1-5 lesions [Table - 2].

Majority of the patients presented with lesions only over the face. Lesions over trunk, upper limb, lower limb, knee and elbow joints were observed in few patients. [3] patients had generalized lesions, all of them being infants.

Investigation revealed anaemia in 33 (16.5%) cases with microcytic, hypochromic picture in most of the cases. Microscopic examination of the stool revealed the presence of ova/cyst in 31 (15.5%) samples. Results of fungal scraping and gram staining of scraped material for bacteria were negative in all cases. Culture for fungus and bacteria from the lesions, did not show any significant growth.

Biopsy of the lesion and histopathological examination were carried out in 15 cases and the features included hyperkeratosis (33.33%), parakeratosis (40%), acanthosis (53.33%), spongiosis (80%) ad perivascular infiltrate (100%). Presence of dense periappendageal and perineural infiltrate was present in 2 patients, suggestive of indeterminate leprosy.

Discussion

Pityriasis alba is found almost entirely in preadolescent children. In most instances, the lesions clear at puberty, however persistence into adulthood has been reported. [2] The exact aetiology of the condition is not known. Various factors like infection, nutritional factors, atopy and dryness of the skin have been implicated.

Pityriasis alba is documented to be more common and more apparent in cold weather, when the skin is dry. [3] In the present study also, exacerbation of the lesions were seen during the beginning of winter. Atopic background has been reported as a predisposting factor for pityriasis aiba. [4] In our study an atopic background was present in 85.5% of patients. Nutritional deficiency, anaemia and parasitic infestations were proposed as contributing factors by Bassaly et al. In the present study only 2% of patients were seen with low growth profile and signs of nutritional deficiencies. However, anaemia was seen in 16.5% of individuals, with a microcytic hypochromic picture in most of them. Bacterial and fungal culture studies failed to reveal any infective aetiology in the present study.

Clinical presentation of the lesions were similar to those described by the previous authors. They usually present as well defined or ill-defined, hypopigmented macules with fine superficial scaling. 7 patients had presented with hypopig mented macules with central hyperpigmentation. Similar type of pigmenting pityriasis alba had been reported earlier also. [5] Generalised pityriasis alba, with widespread involvement of the lesions, usually seen in young adults has been reported by Zaynoun et al. [6] In the present study also, 3 patients with generalized pityriasis alba were encountered, but all of them were infants.

Histopathological findings in the present study is in accordance with the previous studies[7] and it included hyperkeratosis (33.33%), parakeratosis (40%), acanthosis (53.33%), spongiosis (80%) and perivascular infiltrate (100%). Histopathological features of indeterminate leprosy observed in 2 long-standing cases was an interesting observation in the present study.