Letter to the Editor
Half-and-half nail in a case of isoniazid-induced pellagra

Pellagra is a forgotten disease, particularly in developed countries. It is a nutritional disorder characterized by 4 “Ds”: diarrhea, dermatitis, dementia, and death. Causes of pellagra are chronic alcoholism, inadequate diet, malabsorption, metabolic derangement and drugs. Half-and-half nail is an occasional but specific clinical finding in chronic renal failure. We report a case ofIsoniazid-induced pellagra associated with half-and-half nail.
We present a case of a 23-year-old man presenting with a month’s history of a painful, cervicofacial, cutaneous lesion appearing after sun exposure, initially as an acute onset of erythema that progressed to a bullous surface, exudative plaque. The patient also mentioned bulla on the dorsum of his feet, which evolved into erosions and crusts. The patient also has cheilitis and glossitis. The patient has a history of 7 years of schizophrenia, with long-term oral administration of clozapine and risperidone. Five months ago, because of recurrent diarrhea, the local hospital diagnosed “secondary pulmonary tuberculosis” , with oral administration of rifampicin 0.45 g qd, isoniazid 0.3 g qd for 4 months, and ethambutol 0.5 g qd, pyrazinamide 0.75 g qd for 2 months.
He had no history of alcoholism. His physical examination was normal. On dermatological examination, symmetric, well-defined, red to brown colored, scaly eruptions were observed on his face, front of the neck, resembling a necklace (Casal’s necklace), dorsa of his hands/feet and extensor surface of the forearms. Visible bulla on the dorsum of his feet, erosion, exudation plaque on pelma. Scrotal and perineal erythema and erosions can also be seen. The proximal half of the nails of his hands were white and the distal portion were pinkish-red with a sharply demarcated contrast between the 2 zones (Figures 1–4). He stated that the nail changes occurred at the same time as the skin lesions. The laboratory tests (glucose, urea, creatinine, liver function tests, urine analysis, hemoglobin, hematocrit, creatinine clearance, complement and immunoglobulins, thyroid hormones) were within normal limits. Antinuclear antibody and anti-DNA antibody were negative. A skin biopsy showed hyperkeratosis, perivascular lymphohistiocytic infiltrate in the dermis and vacuolar degeneration of the basal layer (Figure 5).
Pellagra was diagnosed clinically and histopathologically. Half-and-half nail was diagnosed clinically. Isoniazid (INH) treatment was not...


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