Ichthyosis is a group of genetic keratinization disorders characterized by excessive scaling that is associated with hyperproliferative epidermis and/or cellular retention. Whereas normal outer epidermis thickness is 25 ÎŒm, it can be 10-fold greater in patients with ichthyosis. As a result, photoactivation of 7-dehydrocholesterol is impaired, causing systemic vitamin D deficiency.In this case series, 25 patients with congenital ichthyosis with vitamin D deficiency (<10 ng/mL) were supplemented with 60,000 IU of vitamin D3 for 10 days followed by daily allowance of 400 to 600 IU of vitamin D3 and 40 mg/kg per day of elemental calcium. The authors assessed improvement in cutaneous scaling and body and tested patients' blood and urine samples at day 1, day 10, 1 month, and 3 months. They also documented patients' Dermatology Life Quality Index score before and after treatment.All patients had normal vitamin D levels; supplementation was discontinued for two patients who reached a level of 100 ng/mL within 10 days. Subjective improvement of symptoms (dryness of the skin, allergic rhinitis, tightness of the skin, and scaling) was observed by both the provider and the patients. There was remarkable improvement in symptoms of severe ichthyosis such as lamellar ichthyosis (tightness of the skin and scaling). Marked improvement in Dermatology Life Quality Index score was also noted.This case series demonstrated remarkable symptomatic relief with vitamin D supplementation in patients with congenital ichthyosis; however, additional research should be conducted with larger sample sizes to support these findings.