During examination, the patient was observed repetitively cracking his knuckles, making a fist with the right hand, placing the left hand on top, and rubbing the hand, a behavior he routinely did multiple times daily. The observed pattern of finger involvement on the dorsum of the right hand corresponded to areas subjected to significant pressure during the described activity. Consequently, a diagnosis of lichen simplex chronicus (LSC) secondary to mechanical rubbing, along with associated pachydermodactyly on the fingers of the right hand, was established.
Lichen simplex chronicus and pachydermodactyly are both attributed to microtrauma inflicted upon the skin. Lichen simplex chronicus often constitutes a diagnosis of exclusion and is characterized by repetitive trauma-induced keratinocyte proliferation and melanocyte activation, resulting in hyperpigmentation and skin thickening. Although typically observed in women between the fourth and fifth decades of life, LSC is rarely reported in children. In adults, LSC-related rubbing or scratching frequently arises from chronic pruritic dermatitis such as eczema or psoriasis, neurodermatitis from dysesthesia, or habitual movements, as exhibited by this young patient. While generally benign, LSC may become infected. In rare instances, malignant transformation may occur.
The association with pachydermodactyly implicates microtrauma, necessitating careful observation and questioning to elucidate the cause, as demonstrated in this case. Lesions are typically hyperpigmented, though cases of associated hypopigmentation or depigmentation have been documented. Affected areas typically fall within the patient’s hand and finger reach, with lesion improvement over several months achievable through trigger avoidance.
Pachydermodactyly, a rare but benign fibromatosis around the proximal interphalangeal joints, is often misdiagnosed as juvenile idiopathic arthritis, potentially leading to unnecessary treatments and patient anxiety. Microtrauma history due to digit manipulation is prevalent among affected individuals, with most also exhibiting neuropsychiatric disorders. Histological examination of pachydermodactyly reveals hypergranulosis and dermal thickening, accompanied by increased fibroblasts and collagen types I, III, and V, differing from the epidermal changes seen in LSC.
The differential diagnosis also included phytophotodermatitis, a phototoxic dermatologic reaction following exposure to ultraviolet light subsequent to contact with furocoumarin-containing plant chemicals. However, the persistence of the patient’s lesions for over a year precluded this diagnosis. Secondary hyperpigmentation was also contemplated but excluded due to the absence of preceding inflammatory dermatitis.
Dr. Catalina Matiz
Treatment of LSC primarily involves identifying and addressing any underlying conditions, repairing the skin barrier, reducing inflammation, and modifying behaviors contributing to chronic microtrauma, as observed in this patient. Topical corticosteroids may aid in decreasing epidermal thickening and discoloration, though lesion resolution necessitates behavior cessation.
It’s important to identify these types of skin changes in children to avoid unnecessary medical treatments for these benign conditions.
Dr. Matiz is a pediatric dermatologist at Southern California Permanente Medical Group, San Diego.
Suggested Reading
Seier JA, Dissemond J. Lichen Simplex Chronicus Due to Mechanical Irritation. Dtsch Arztebl Int. 2022 Nov 18;119(46):802. doi: 10.3238/arztebl.m2022.0213.
Small S et al. A 12-Year-Old Boy Presenting With Unilateral Proximal Interphalangeal Joint Swelling. BMJ Case Rep. 2011 Apr 13:2011:bcr0120113719. doi: 10.1136/bcr.01.2011.3719.
Voicu C et al Lichen Simplex Chronicus as an Essential Part of the Dermatologic Masquerade. Open Access Maced J Med Sci. 2017 Jul 24;5(4):556-557. doi: 10.3889/oamjms.2017.133.