neurofibromatosis affects 1:3,000 individuals , and characterized by largely benign but often debilitating tumors that grow in the nervous system . its course is unpredictable : it can cause a variety of benign nerve tumors including plexiform , dermal , and optic glioma tumors ; in some cases malignant peripheral nerve sheath tumors can develop in the plexiform tumours . down 's syndrome is one of the most common and easily recognized genetic conditions in humans . the estimated prevalence in the united states is approximately 15 per 10,000 live births ( ie , 1 out of every 700 ) most often , it is the result of nondisjunction on chromosome 21 during maternal meiotic division . we herein present the case of a 17-year - old boy with complaints of skin lesions over the back associated with mild itching since 3 months . he was a known case of down 's syndrome with a history of seizures in childhood [ figure 1 ] . the lesions gradually increased in size and number , and similar lesions started developing over his forehead since 23 weeks . on examination , multiple skin colored papules of varying size were present over the entire back and the forehead . velvety thickening of the skin and hyperpigmentation of the axillae suggestive of acanthosis nigricans was present . the characteristic features of down 's syndrome , including simian crease , mongoloid facies , and mental retardation were present . canities and a solitary keloid over the chest were also seen apart from the clinical features of down 's syndrome . on oral examination , scrotal tongue , abnormal dentition , and other investigations such as ct scan brain , 2d echo , and ecg were normal . histopathology of the nodule from the back revealed focally thinned out epidermis with intact basal layer ; the papillary dermis showed a mild perivascular infiltrate . deeper dermis showed a benign spindle cell proliferation suggestive of neurofibromatosis [ figure 3 ] . physical appearance of down 's syndrome ( a ) neurofibromas ( b ) sebaceous cyst ( c ) acanthosis nigricans , and axillary freckling ( d ) scrotal tongue focally thinned out epidermis with intact basal layer with the papillary dermis showing a mild perivascular infiltrate . the presentation of a patient with two unrelated genetic disorders is uncommon , although not statistically impossible . however , in two of these reports , a third medical condition was also present . in one report , breast cancer was reported . in the other , our patient had down 's syndrome , neurofibromatosis , dental anomalies , and ocular defects and keloids . in the large majority of cases , trisomy 21 there is no current evidence to support the idea that this is anything other than a chance occurrence . the two conditions are not related , and the likelihood of a person being born with these two conditions is approximately 1 in 2,700,000 births . they however overlap in their manifestations . both are associated with intellectual impairment to differing degrees . macroglossia occurs in both conditions , as may facial , dental , and occlusal abnormalities . hearing and speech are affected in both conditions , as may the ability to maintain an acceptable level of oral hygiene . mutations in the gene results in abnormal control of cell growth , differentiation , and aberrant myelination . our patient with of neurofibrmatosis type 1 with down 's syndrome is the first such to have a keloid and sebaceous cyst apart from myopia and dental anomalies . the unpredictable nature and course of the two genetic disorders along with multiple acquired conditions in this patient make it difficult for patients , teachers , care givers , and medical / dental providers to create and maintain long - term care plans . the authors certify that they have obtained all appropriate patient consent forms . in the form the patient(s ) has / have given his / her / their consent for his / her / their images and other clinical information to be reported in the journal . the patients understand that their names and initials will not be published and due efforts will be made to conceal their identity , but anonymity can not be guaranteed . the authors certify that they have obtained all appropriate patient consent forms . in the form the patient(s ) has / have given his / her / their consent for his / her / their images and other clinical information to be reported in the journal . the patients understand that their names and initials will not be published and due efforts will be made to conceal their identity , but anonymity can not be guaranteed .
we report a patient with down 's syndrome and neurofibromatosis who presented with a keloid , sebaceous cyst and acanthosis nigricans , along with dental and ophthalmological defects . 
 the coexistence of neurofibromatosis type 1 and down 's syndrome which are two unrelated genetic conditions is itself a rarity .