CASE REPORT

Male 25-year-old patient, with history of mental retardation since birth, referring asymptomatic nodules on the hands that appeared about two years before and had progressively increased in size. Three months before the visit they had noticed similar lesions on the feet and right knee. The family did not report repetitive hand trauma or similar cases in the family.

General physical examination showed no abnormalities.
The dermatological examination showed nodules of fibroelastic consistency located on the lateral aspect of the right 2nd metacarpophalangeal joint (Figure 1), medial aspect of left 1^st metacarpophalangeal joint, back of bilateral first toe phalanges (Figure 2) and calcaneous. The skin around the proximal phalanges of the fingers and extensive aspect of the right knee was thickened.

Complementary tests were normal: complete blood count and uric acid (4.4 mg/dl). Hand x-ray: preserved bone morphology; maintained articular interlines; minor enlargement of soft parts at 3rd and 4th interphalangeal areas on the right and bilateral 2nd metacarpophalangeal area. Absence of periosteal thickness. Feet x-ray: normal bone texture and morphology, no evidence of focal bone lesions.

Soft part ultrasound of the hands showed solid formations with signs of vascularization inside it, heterogeneous and partially defined limits in the subcutaneous plan, measuring 2.5 X 0.9 X 1.8 cm on the basis of the right 2nd finger and 2.6 X 1.7 X 0.9 cm on the basis of left 1^st toe.

Skin histopathology test of the right 2^nd finger revealed marked thickness of dermis with hyperkeratosis. In the deep dermis, there was proliferation of fibroblasts and collagen fibers (Figure 3 and 4). Staining with colloidal iron showed mucin increase in the dermis (Figure 5).

The management approach was intralesion infiltration with triamcinolone acetonide at the concentration 20mg/ml, which led to regression of lesions after three applications.

DISCUSSION

Pachydermodactyly is a benign and non-painful condition that produces edema and skin thickness around the dorsal and lateral regions of phalanges and proximal interphalangeal joints of the fingers ⁴.

Several types of pachydermodactyly have been described depending on topography, etiology and pathological associations: 1) classical, in which there is affection of many fingers of both hands, which is attributed to local trauma; 2) monopachydermodactyly or localized pachydermodactyly, with affection of only one finger; 3) transgrediens pachydermodactyly in which there is skin thickness reaching other areas in addition to the fingers, such as metacarpophalangeal regions; 4) familial pachydermodactyly, and 5) pachydermodactyly associated with tuberous sclerosis 4. The case herein described corresponds to transgrediens pachydermodactyly,which includes involvement of fingers, metacarpal and metatarsophalangeal joints, in addition to plantar region and the right knee. The association of pachydermodactyly with pachydermal aspect on the knee had never been described. Only one report of association with plantar pachydermia was found ⁵.

Transgrediens type is an exceptional form of pachydermodactyly, with few cases described in the literature. It is characterized by extension of skin thickness of the fingers to metacarpophalangeal regions. In our patient, this fact was observed in the involvement of the left 1st metacarpophalangeal joint and the right 2nd metacarpophalangeal joint. Moreover, there was pachydermal aspect on the regions of calcaneous, metatarsophalangeal joints and right knee ⁶.

The etiology of pachydermodactyly remains unknown. It is normally an acquired disease, even though there are some publications that document family cases ^{4, 7}. It has been suggested that repetitive mechanical traumas, such as the habit of rubbing the fingers, could lead to skin thickness ¹. In the case reported here, there was no repetitive stimuli of the fingers, even though the patient had intellectual deficit.

Histopathology analyses normally reveal hyperkeratosis and significant thickness of dermis owing to deposits of collagen fibers, with different levels of cellularity. These findings are compatible with those observed in the patient described here. Collagen types III and V were increased and electron microscopy showed increase of fine collagen fibers. There might have been mucin depositsamong collagen fibers ⁸.

Differential diagnosis of pachydermodactyly should be made with knuckle pad, whose distinction is made through the location of volume increase around the proximal interphalangeal joints: dorsal in the knuckle pad and predominantly lateral in pachydermodactyly. Moreover, knuckle pad may be found in both genders within a broad age range ¹. Other possible differential diagnosis are foreign body granuloma, fibroma and arthropathy ⁹. There should be no confusion with pachydermoperiostosis, in which there is dominant autosomal heritage, digital clubbing, and bone and scalp findings ^{10, 11}.

The coexisting conditions related with pachydermodactyly include tuberous sclerosis, macular atrophy varioliform cutis, Dupuytren contracture, carpal tunnel syndrome, and Ehlers-Danlos syndrome ⁸.

Treatment of pachydermodactyly consists of suspension of repetitive mechanical stimuli (if applicable), use of intralesion corticoid or complete excision of the lesion 11. In the care reported here, we used treatment with infiltration of intralesion corticoid, which led to significant improvement of lesions.

Pachydermodactyly is a rare disease, not very well known and probably under notified. We have reported a case of transgrediens pachydermodactyly associated with plantar and knee involvement, which had never been described in the literature.

REFERENCES