Primary amyloidosis is caused by a monoclonal proliferation of plasma cells and is capable of producing cutaneous lesions. A 56-year-old male was admitted to the hospital for evaluation of chronic back pain and acute lower extremity weakness. On examination, he was noted to have subungual verrucous plaques with overlying nail dystrophy on his bilateral thumbs. A biopsy of one subungual lesion showed a deposition of amorphous material in the dermis that stained with Congo red and crystal violet. These cutaneous lesions ultimately led to the diagnosis of plasma cell dyscrasia and primary amyloidosis. Based on the literature search, primary amyloidosis presenting with this degree of subungual thickening and overlying nail dystrophy has not been previously reported.
BACKGROUND. Corneocytes of the nail plate, like those of the stratum corneum, generate cornified envelopes (CEs) of cross-linked protein that can be visualized readily after removal of non-cross-linked protein by detergent extraction. Defective CE formation occurs in epidermal scale and hair in transglutaminase 1 (TGM1)-negative lamellar ichthyosis (LI) and has been proposed as a diagnostic aid for this syndrome. OBJECTIVES. (i) To ascertain whether TGM1 is important for CE formation in nail; (ii) to characterize CE abnormalities occurring in LI that may be distinguished from other types of inherited ichthyosis when nail samples are subjected to detergent extraction; and (iii) to evaluate the utility of nails as a diagnostic aid for LI. METHODS. Nail samples were provided by nine patients previously classified as having TGM1-negative LI, four with other types of ichthyotic conditions and six normal controls. Samples were extracted extensively in sodium dodecyl sulphate under reducing conditions and examined by light and electron microscopy. RESULTS. After extraction, defective CE cross-linking was visualized in epidermal corneocytes from seven of nine patients exhibiting TGM1-negative LI, whereas nail samples from patients with the other syndromes were normal. The defects in CE structure resembled those recently reported for LI scale, although in some cases residual CE and CE-associated structures were present. CONCLUSIONS. Despite the paucity of clinical nail symptoms in LI, TGM1 activity is important for generation of normal CE in nail plate, consistent with its importance in protein cross-linking in interfollicular epidermis and hair. Lack of this activity leads to a strikingly aberrant appearance of CE in LI nail after detergent extraction that is evident ultrastructurally in a large majority of cases. Nail envelopes therefore could provide a useful diagnostic tool in distinguishing LI from other ichthyoses with overlapping clinical features.
Congenital malalignment of the great toenail is characterized by lateral deviation of nail plates, which are not parallel to the distal phalanx. We report two cases of congenital malalignment of the great toenail in two otherwise healthy children. Because this entity is probably underdiagnosed, a high index of suspicion is required to prevent from diagnostic errors and unnecessary treatments.
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