We report a 6 year old girl with an isolated humoral immune deficiency and a unique combination of dysmorphic features. Physical findings include microcephaly, micrognathia, sickle shaped eyebrows, hypoplastic alae nasi, thenar hypoplasia, partial 4-5 syndactyly of toes, recessed great toes, anterior anus, and hypoplastic labia minora. Radiographic findings include triphalangeal thumbs and hypoplastic first metatarsals. She has postnatal growth retardation and her development is substantially slower than her twin's. Her clinical course has been complicated by recurrent sinopulmonary infections and pneumococcal bacteraemia. Laboratory evaluation revealed hypogammaglobulinaemia, absent B cells, and a 46,XX karyotype. A review of the literature and the London Dysmorphology Database did not produce any recognizable syndromes that match her constellation of findings. She may represent a unique syndrome of unknown etiology.