|Year : 1992 | Volume
| Issue : 4 | Page : 266-267
A peculiar skin lesion characterized by hyperpigmented, dry, hyperkeratotic plaques affecting the lower thirds of the thighs was seen frequently in patients with chronic obstructive pulmonary disease. It is attributed to intermittent irritation secondary to a characteristic dyspnoeic posture often assumed by these patients.
Keywords: Thinker′s sign, Target sign
|How to cite this article:|
Pavithran K. Thinker's sign. Indian J Dermatol Venereol Leprol 1992;58:266-7
| Introduction|| |
Many skin lesions are known to develop as markers of systemic diseases. A peculiar skin lesion strictly localised to the lower-thirds of the front of the thighs was frequently observed in patients suffering from chronic obstructive pulmonary disease (COPD). Two such representative cases are reported here.
| Case Reports|| |
Case 1 : A 52-year-old woman suffering from COPD due to bronchial asthma for 20 years, was seen for asymptomatic, diffuse, dry, hyperpigmented and hyperkeratotic plaques of 6x14 cm on the right and 4x5 cm on the left lower- thirds of the front of thighs just above the knees [Figure - 1]. There were no other skin lesions elsewhere on the body. Examination revealed barrel shaped chest with markedly decreased breath sounds. Upper airway rhonchi were heard all over the lung fields. During an attack of acute dyspnoea, she was observed to lean forward while sitting in attempt to relieve dyspnoea. She supported her trunk by resting the elbows on her lower thighs [Figure - 2]. On further questioning she related her skin lesions to sitting in this posture for many hours each day to help her breathing. X-ray of the chest revealed depressed hemidiaphragms and hyperlucent lung fields. Histological study of the skin lesion revealed only marked hyperkeratosis. Partial regression of the skin lesion occurred following application of 3% salicylic acid ointment.
Case 2 : A 62-year-old man suffering from COPD due to chronic bronchitis for 8 years was seen for asymptomatic dry, hyperkeratotic, hyperpigmented plaques of 12x6 cm on the front of lower-thirds of both things. The chest was emphysematous and breath sounds were highly diminished. Coarse rhonchi were heard all over the lung fields and the percussion note was hyperresonant. He also was in the habit of sitting and• leaning forward supporting the weight of his trunk by placing the elbows on his thighs to help his breathing. X-ray of the chest showed features of emphysema. Histology of the skin lesion revealed marked hyperkeratosis. Topical keratolytic containing 10% urea resulted in partial regression of the skin lesion.
| Comments|| |
The strict localization of the hyperkeratotic skin lesions on the front of lower thigh suggested that it resulted from chronic intermittent irritation secondary to a characteristic dyspnoeic posture often assumed by patients with COPD. Non-pruritic nature of the skin lesions and absence of inflammatory changes in histology excluded the possibility of lichenified eczema which often develops in patients with bronchial asthma. Rothenberg in 1963 described this type of skin lesions as marker of COPD and be name it as `thinker's sign.  He attributed it to the instinctive assumption of a characteristic sitting posture by patients with advanced respiratory insufficiency. Dahl also observed similar skin lesions in patients with emphysema.  Whitesides in 1979 observed circumscribed hyperkeratotic palques on the knees of patients with COPD and named it as `Target sign of emphysema. 
| References|| |
|1.||Rothenberg HJ. The 'thinker's sign'. J A M A 1963; 184: 902-3. [PUBMED] |
|2.||Dahl K V. Emphysema. Arch Dermatol 1970; 101: 117. |
|3.||Whiteside JR. Target sign for emphysema. Chest 1979; 75: 530. |
[Figure - 1], [Figure - 2]