The hair loss that occurs in hereditary vitamin D dependent rickets type IIA is similar to APL/AUC. It’s a rare AR disorder too. Hair is present at birth and then lost in the with 12 months. Hair is usually lost between 1-3 months. There can sometimes be some eyebrow and lashes remaining. The clinical and sometimes even the pathology can be similar to APL. In fact, some patients with VDDR alopecia have small milia.
Bergman et al, 2005
A study in 2005 set out to compared 6 patients with VDDR with and 4 with AUC/APL
Histology of VDDR patients showed lower 2/3 of hair follicle missing and cysts in the mid upper dermis and sometimes lower too.
The pathology of APL/AUC was similar with lower 2/3 of hair follicle missing and cysts in the mid upper dermis and sometimes the lower too.
Surprisingly, the histological findings of VDDR and APL/AUC are essentially similar. The only normal part is in the infundibulum. SG are present but they are devoid of hairs. The lower part is missing and replaced with irregular epithelial structures with small cystic dilations or by small epithelial cysts.
In some ways, all of this is should probably not be surprising given that hairless mice and VDR knockout mice are so similar.
