A Descriptive study of lesions following the lines of Blaschko

Sheerja, Bali (2012) A Descriptive study of lesions following the lines of Blaschko. Masters thesis, Madurai Medical College, Madurai.


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INTRODUCTION : The concept of Blaschko’s lines was first put forth by Alfred Blaschko, a private practioner in dermatology, when he presented his findings on the distribution patterns of linear skin at the German Dermatological Society meeting in Breslau in 1901. In his original description he referred to Blaschko’s lines as ‘a system of lines on the human skin which the linear nevi and dermatosis follow.’1 The pattern of Blaschko’s lines does not correlate with the distribution of cutaneous nerves, blood vessels, or lymphatics and is distinct from pigmentary demarcation lines. Two mechanisms have been proposed to explain Blaschko’s lines: mosaicism and chimerism. A number of congenital and acquired conditions follow these special lines. Almost all epidermal nevi follow Blaschko’s lines. Lesions in various X-linked disorder’s like incontinentia pigmenti, Goltz syndrome and chromosomal disorders like hypomelanosis of Ito also respect these lines. This pattern followed by these congenital diseases helps in their diagnosis not only in the newborn and infant, but also in adults. Other nevoid epidermal disorders like linear lichen planus, nevoid psoriasis, Darier’s disease and Hailey- Hailey disease, linear porokeratosis and blaschkitis are some of the acquired diseases that occur along the Blaschko’s lines. The occurrence of these acquired lesions has been known to have special significance with regards to the epidemiology, clinical presentation, treatment and prognosis. There have been many studies with respect to individual diseases following the lines of Blaschko. However, no studies with Blaschko’s lines as the central focus could be found in the literature. This study is an attempt in that direction. AIM OF THE STUDY : 1) To study and describe the patterns of Blaschko’s lines encountered in various dermatoses. 2) To study the clinico-epidemiological features of various diseases related to the lines of Blaschko. MATERIALS AND METHODS : This study was conducted in the Out Patient Department of Government Rajaji Hospital, Madurai during the period October 2009 to September 2011 (24 months). INCLUSION CRITERIA: All consenting patients with - 1. Lesions related to Blaschko’s lines whose diagnosis could be confirmed on clinical basis alone. 2. Lesions related to Blaschko’s lines that were confirmed by histopathology where clinically there was a diagnostic dilemma. EXCLUSION CRITERIA: 1. Patients not willing to give consent. 2. Patients with lesions related to Blaschko’s lines, but where the diagnosis could not be confirmed on clinical basis and histological and other relevant investigations could not be performed due to various reasons. After applying the criteria mentioned above, cases were enrolled. After their informed consent thorough dermatological and systemic examination was conducted. The parameters studied were the age of onset, sex, side of involvement, site, type of Blaschko pattern followed, symptoms, extension/ regression of the lesions and direction of extension of the lesions, associations, family history and birth history. No literature clearly defining the width of narrow and broad – band types of Blaschko’s lines could be found. Hence, in this study we have arbitrarily categorized Blaschko’s lines in the type 1 pattern with width less than 3 centimeters to be narrow – band and those with a width more than 3 centimeters to be broad- band. Skin biopsy was done in cases where there was doubt in diagnosis. Relevant investigations like Chest X Ray, EEG, CT -Brain were carried out wherever necessary. SUMMARY : 1. A total of 218 cases of lesions following Blaschko’s lines were encountered in the two year study period. 2. Lesions following the lines of Blaschko constituted about 2 in 1000 cases visiting the Dermatology OPD. 3. Various dermatoses occurred along the lines of Blaschko, of which the most common was lichen striatus. 4. Overall, the lesions following Blaschko’s lines were more common in females. 5. The most common dermatoses following Blaschko’s lines in infancy were nevus achromicus and epidermal nevi; in toddlers and young children was lichen striatus; and in adults was linear lichen planus. 6. The overall side distribution of these lesions in various dermatoses was equal. 7. The most common pattern of Blaschko’s lines occurring in various dermatoses was the narrow- band pattern followed by the broad- band pattern and a combination of the two. Phylloid pattern and lateralization were most commonly encountered in nevus achromicus. 8. Lichen striatus was more common in females, and the most common age group affected was that of 1-5 years. Narrow- band was the predominant type of Blaschko’s lines followed by lichen striatus. The most common site involved was the thigh. 9. Linear lichen planus was more common in females, the average age of onset being 31 years. The predominant type of Blaschko’s lines followed was the narrow- band pattern. The most common site of involvement was the legs. Oral mucosal and nail involvement were less common in linear LP. 10. Nevus achromicus was more common in males, the lesions being present at birth in most cases. The predominant side involved was the left side. The most common type of Blaschko’s lines followed was the narrow- band type, followed by the phylloid pattern. The most common site involved was the chest. One patient had nail involvement. 11. Most epidermal nevi presented within the first 2 weeks of life and were more common in males. The left side was more frequently affected. Most epidermal nevi occurred along the narrow band pattern, the head and neck being the most common site of involvement. Epidermal nevi were not associated with developmental defects in this study. 12. The less common disorders of pigmentation that followed Blaschko’s lines included linear whorled nevoid hypermelanosis, hypomelanosis of Ito and linear vitiligo. 13. Developmental abnormalities in hypomelanosis of Ito and LWNH were not found to be as common as given in the literature. 14. Linear morphea followed the lines of Blaschko, despite the controversies stated earlier. 15. Sebaceous nevi occurred along Blaschko’s lines, and were also noted to develop in older age. 16. Certain diseases like Darier’s disease, lichen nitidus, lichen planus pigmentosus, LSA infrequently occurred along the Blaschko’s lines. 17. Interesting findings included were three cases of nevoid psoriasis, reflecting that this condition is probably not as rare as thought to be. 18. A unique observation made was the presence of revertant mosaicism in dyschromatosesis universalis hereditaria wherein sparing of areas of normal skin along the lines of Blaschko occurred. 19. A rare finding encountered of was soft fibroma occurring along the Blaschko’s lines. 20. Conditions like nevoid psoriasis and nevus achromicus were found to be associated with developmental and neurological abnormalities. Hence, it may be prudent to evaluate and follow such cases regularly. 21. Only a few cases required biopsy for the confirmation of diagnosis, which was done in the study. CONCLUSION : The incidence of lesions following the lines of Blaschko is 2 per 1000 dermatological cases, the most common disease being lichen striatus followed by linear lichen planus, nevus achromicus and epidermal nevus. The infrequently encountered diseases are linear whorled nevoid hypermelanosis, hypomelanosis of Ito, nevoid psoriasis, sebaceous nevi, linear morphea, linear vitiligo, Darier’s disease, lichen nitidus, lichen sclerosus, lichen planus pigmentosus and incontinentia pigmenti. Lesions following Blaschko’s lines are more common in females. The most common type of Blaschko’s lines followed is the narrow- band. The age of onset distribution shows two peaks constituted by nevus achromicus and epidermal nevi in the first 1 year of life and by lichen striatus in the toddler age group. Disorders like nevus achromicus and nevoid psoriasis can also be associated with congenital defects. Rarely, soft fibroma can follow the lines of Blaschko and sparing of the skin along the Blaschko’s lines can occur in dyschromatosis universalis hereditaria. To the best of our knowledge, this is the first study of its kind. More similar studies are needed for further comparisons and validation. The obstacle faced in this study was the lack of a clear distinction between narrow and broad – band patterns of Blaschko’s lines. Thus there is a need to reach a clear and universal definition of the various types of Blaschko’s lines. The differences in the course, prognosis and treatment aspects of various dermatoses following the Blaschko’s lines as compared to the generalized forms of the diseases are not yet completely elucidated. Hence, further studies in this direction will be of profound help in the management of such cases.

Item Type: Thesis (Masters)
Uncontrolled Keywords: Blaschko ; lesions ; Descriptive study.
Subjects: MEDICAL > Dermatology Venereology and Leprosy
Depositing User: Subramani R
Date Deposited: 02 Mar 2018 03:57
Last Modified: 03 Mar 2018 03:05
URI: http://repository-tnmgrmu.ac.in/id/eprint/5976

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