Niacin or tryptophan deficiency causes pellagra. Isoniazid interferes with the absorption of niacin and individuals on Isoniazid (INH) are at risk of pellagra. Isoniazid preventive therapy (IPT) is the administration of isoniazid to immunosuppressed individuals to prevent active tuberculosis (TB). IPT, in sub-Saharan Africa, the region worst hit by HIV and with a high TB prevalence, is recommended. A 40-year-old, HIV+ Zambian woman on Antiretroviral therapy for five years and IPT for three months presented with a four-day history of constipation, generalised body weakness and irrelevant talk. She complained of a generalised rash, sloughing off, and darkening of the skin on the face, neck, forearms, and dorsum of both feet. A physical examination revealed features of pellagra, and rapid response to oral niacin reaffirmed the diagnosis of pellagra. Unlike typical cases of pellagra presenting with the classic 3 Ds of Diarrhoea, Dementia and Dermatitis, our patient presented with constipation instead of diarrhoea. A consideration of Pellagra in HIV+ patients on IPT whose diet is mostly maize-based will be beneficial, even if the classic 3 Ds of diarrhoea, dementia, and dermatitis are not wholly present. A timely diagnosis and prompt treatment of pellagra can be lifesaving.