Indian Journal of Dermatology
: 2007  |  Volume : 52  |  Issue : 3  |  Page : 141--144

Hyperpigmented keratotic plaques below the elbow and above the knee: An unexplored entity?

Sujata Sengupta, Jayanta Kumar Das, Asok Gangopadhyay 
 Department of Dermatology, RKM Seva Pratisthan and Vivekananda Institute of Medical Sciences, Kolkata, India

Correspondence Address:
Sujata Sengupta
UV-24/3C, Udayan, 1050/1, Survey Park, Kolkata - 700 075


Background: Hyperpigmented keratotic lesions below the elbow and above the knee are common, but not yet described in the literature. Aim: To clinicopathologically analyze the lesions to find out their etiology, aggravating factors, associated diseases and histopathological features. Materials and Methods: Thirty patients having such lesions were subjected to detailed history-taking and clinical examination. A biopsy from the local area was performed in all the cases. The data obtained was statistically analyzed. Results: The commonest age group affected comprised of middle-aged females. In 50% cases, friction played an important role, and in the rest, no cause was found. Majority of patients had no other dermatological or systemic disorders. Nonspecific histopathologic changes were observed in 60%. Conclusion: Our study points towards the existence of an idiopathic hyperpigmentation around the elbow and knee that is common and not associated with any other skin disorder and is histologically nonspecific.

How to cite this article:
Sengupta S, Das JK, Gangopadhyay A. Hyperpigmented keratotic plaques below the elbow and above the knee: An unexplored entity?.Indian J Dermatol 2007;52:141-144

How to cite this URL:
Sengupta S, Das JK, Gangopadhyay A. Hyperpigmented keratotic plaques below the elbow and above the knee: An unexplored entity?. Indian J Dermatol [serial online] 2007 [cited 2023 Dec 3 ];52:141-144
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Hyperpigmentation of the skin below the elbow and above the knee is a dermatological condition that is encountered frequently. However, patients are usually not bothered by this common condition and friction has often been accepted as the causative factor. However, surprisingly, this condition is not being described in textbooks to date. There are no instances in literature, and our thorough Medline search did not reveal this entity. The purpose of our study was to clinicopathologically analyze the hyperpigmented lesions below the elbow and above the knee to find out the etiology, incriminating factors, associated diseases and histopathological features.

 Materials and Methods

The study was undertaken in the outpatient Department of Dermatology in our hospital from January 2004 to July 2005. The 30 patients who were taken into consideration had either hyperpigmented keratotic lesions on the dorsal aspect of the forearm just below the elbow joint or similar lesions on the ventral aspect of legs above the knee joint or both. We included patients who sought medical advice for some other dermatological disorders also. The detailed history of all the patients were taken with special reference to age, mode of onset, duration of disease, family history, occupation, habits and tics, cosmetic usage and treatment received. The clinical examination of the local area was followed by thorough dermatological evaluation to detect hyperpigmentation at other sites as well the presence of other skin disorders.

In addition to routine investigations, biochemical tests such as blood sugar, thyroid profile and serum insulin were performed wherever relevant. In all cases, a biopsy was performed from a representative area over the elbow or knee and a clinicopathological correlation was attempted.


The age of the 30 patients ranged from 24 to 69 years with a mean age of 48.2 years and the sex ratio was 1:4 in favor of the females [Table 1]. The maximum number of patients (60%) was in the age group 40-50 years. The mean duration of the disease was 5 months (range: 1 month to 5 years) and six patients (20%) had a family member with similar pigmentation. A history of some form of friction in the local area was present in 14 patients (46.7%), which was related to occupation (e.g., desk jobs), habits (e.g., squatting on the floor) and tics (e.g., rubbing). In 13 patients (43.3%), the pigmentation was asymptomatic.

In more than half of the patients, only the upper limb (53.3%) was involved, followed by both upper and lower limbs in 33% and only the lower limb in 13.3% [Figure 1], [Table 2]. Bilaterally symmetrical involvement was observed in 13 patients (43.3%). In the 18 cases where both the forearms were involved, the left one was affected earlier and to a greater extent in 14 cases (77.8%). Some patients showed a linear extension of the pigmentation along the dorsal aspect of the forearm and the suprapatellar area on the thighs [Figure 2]. The intensities of pigmentation were graded as mild, moderate and severe and were found in 7 (23.3%), 18 (60%) and 5 (16.7%) subjects, respectively. Wood's lamp examination showed epidermal pigmentation in 14 (46.7%), dermal pigmentation in 9 (30%) and mixed pigmentation in 7 (23.3%) cases. Hyperpigmentation elsewhere in the body was found in 11 subjects on the face (13.3%), knuckles (10%), neck (6.7%), axilla (6.7%) and groin (3.3%).

Besides pigmentation, some other local changes were present in many patients (70%), out of which lichenification was commonest (36%) followed by follicular prominence (30%) and xerosis (6.7%) [Figure 3]. While follicular prominence and xerosis occurred earlier, the long-standing cases showed lichenification.

Nineteen out of 30 patients (63.3%) had no other dermatological disorders other than the hyperpigmentation. From the remaining subjects, two subjects each had cutaneous amyloidosis, lichen simplex and atopic dermatitis and two each had psoriasis and acanthosis nigricans (AN). Histopathological changes were nonconclusive in 18 patients (60%) in the form of hyperkeratosis in 55% and a slight increase in the pigmentation of the basal cell layer in 77.8% [Figure 4],[Figure 5],[Figure 6]. In four patients (13.3%), psoriasiform histology with epidermal hyperplasia, hypogranulosis and elongated rete ridges were observed [Figure 7]. However, none of them had clinically evident psoriasis elsewhere. Hyperkeratosis with prominent papillomatosis, hyperpigmentation of the basal cell layer, and characteristics of AN were observed in two cases (10%), from which one had AN at other areas also [Figure 8]. Epidermal hyperkeratosis with rounded dermal papillae containing amyloid deposits was found in two (6.7%) patients, and lichenoid changes with prominent basal cell degeneration in another patient (3.3%)


In clinical practice, we often come across patients with pigmentation of the skin below the elbow and above the knee. In fact, this condition is so common that most people accept it as inevitable and do not seek any medical remedy. For those who do, we clinicians give a symptomatic treatment. Thus far, no references regarding such pigmentation exist in the literature.

Our study reflects that females in the age group of 40-50 are mostly affected by this condition. The absence of children in the study group possibly indicates that the condition preferentially occurs in the adult population. A positive family history in 20% may suggest genetic predisposition. Friction seems to play an important role in many of our patients. The study subjects included teachers and persons engaged in desk jobs where the forearm is habitually in contact with the desk and chair. A few possessed habits such as squatting on the floor to read and write with the arms resting on the floor. Others gave a history of a chronic rubbing of the local area. In most of these cases, the left elbow was more involved in a right-handed person and vice versa. This finding is in support of friction as a predisposing factor for the pigmentation. However, the same logic does not explain the occurrence of pigmentation above the knee area. Moreover, the cause of pigmentation remained unexplained in those 50% patients without a history of friction. Besides, even though age and sex have no significant effect on frictional properties, [1] most of our study subjects were found to be middle-aged ladies. Frictional callosities may occur over the bony prominences of elbow and knee, [2] however, most of our cases did not have them.

Majority of the patients had no other dermatological disorders other than the pigmentation. Even in the patients who had amyloidosis, lichen simplex, atopic dermatitis, psoriasis or acanthosis nigricans elsewhere, a biopsy from the local area showed nonspecific changes. On the other hand, histopathological features of psoriasis, amyloidosis and lichen planus were observed in a few cases without any associated diseases. Friction is known to play an important role in amyloidosis; [3] however, its features were found in very few cases. Overall, nonspecific changes formed the majority.

Our study, even though small, points toward the existence of an unexplained hyperpigmentation below the elbow and above the knee that is sometimes related to friction, usually unassociated with any skin disease and shows a nonspecific histology. The absence of this entity in foreign literature additionally indicates that it is a condition that preferentially occurs in the pigmented races.


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2Pavithran K. Disorders of keratinization. In : Valia RG, Valia AR, editors. IADVL Textbook and Atlas of Dermatology. 2 nd ed. Bhalani Publishing House: Mumbai; 2001. p. 799-834.
3Black MM, Gawkrodger DJ, Seymour CA, Weismann K. Metabolic and nutritional disorders. In : Champion RH, Burton JL, Burns DA, et al , editors. Rook/Wilkinson/Ebling Textbook of Dermatology. 6 th ed. Blackwell Science: Oxford; 1998. p. 2577-677.