Functionally, the subcutaneous fat insulates the body, absorbs trauma, and serves as a reserve energy source.Conditions of the human integumentary system constitute a broad spectrum of diseases, also known as dermatoses, as well as many nonpathologic states (like, in certain circumstances, melanonychia and racquet nails). While only a small number of skin diseases account for most visits to the physician, thousands of skin conditions have been described. Classification of these conditions often presents many nosological challenges, since underlying etiologies and pathogenetics are often not known. Therefore, most current textbooks present a classification based on location (for example, conditions of the mucous membrane), morphology (chronic blistering conditions), etiology (skin conditions resulting from physical factors), and so on. Clinically, the diagnosis of any particular skin condition is made by gathering pertinent information regarding the presenting skin lesion(s), including the location (such as arms, head, legs), symptoms (pruritus, pain), duration (acute or chronic), arrangement (solitary, generalized, annular, linear), morphology (macules, papules, vesicles), and color (red, blue, brown, black, white, yellow). Diagnosis of many conditions often also requires a skin biopsy which yields histologic information that can be correlated with the clinical presentation and any laboratory data.
Bare lymphocyte syndrome
Chronic granulomatous disease (Bridges–Good syndrome, chronic granulomatous disorder, Quie syndrome)
Common variable immunodeficiency (acquired hypogammaglobulinemia)
Complement deficiency
DiGeorge syndrome (DiGeorge anomaly, thymic hypoplasia)
Graft-versus-host disease
Griscelli syndrome
Hyper-IgE syndrome (Buckley syndrome, Job syndrome)
Immunodeficiency with hyper-IgM
Immunodeficiency–centromeric instability–facial anomalies syndrome (ICF syndrome)
Isolated IgA deficiency
Isolated primary IgM deficiency
Janus kinase 3 deficiency
Leukocyte adhesion molecule deficiency
LIG4 syndrome
Myeloperoxidase deficiency
Neutrophil immunodeficiency syndrome
Nezelof syndrome (thymic dysplasia with normal immunoglobulins)
Omenn syndrome 
Purine nucleoside phosphorylase deficiency
Severe combined immunodeficiency (alymphocytosis, Glanzmann–Riniker syndrome, severe mixed immunodeficiency syndrome, thymic alymphoplasia)
Shwachman–Bodian–Diamond syndrome
Thymoma with immunodeficiency (Good syndrome)
Transient hypogammaglobulinemia of infancy
Warts–hypogammaglobulinemia–infections–myelokathexis syndrome (WHIM syndrome)
Wiskott–Aldrich syndrome
X-linked agammaglobulinemia (Bruton syndrome, sex-linked agammaglobulinemia)
X-linked hyper-IgM syndrome
X-linked hypogammaglobulinemia
X-linked lymphoproliferative disease (Duncans disease)
X-linked neutropenia

Nutrition-related
Nutrition-related cutaneous conditions are caused by malnutrition due to an improper or inadequate diet. Biotin deficiency
Carotenemia
Essential fatty acid deficiency
Folic acid deficiency
Hypervitaminosis A
Hypovitaminosis A (phrynoderma)
Iron deficiency 
Kwashiorkor
Lycopenemia
Maple syrup urine disease
Marasmus
Niacin deficiency (pellagra, vitamin B3 deficiency)
Selenium deficiency
Vitamin B1 deficiency (beriberi, thiamine deficiency)
Vitamin B12 deficiency (cyanocobalamin deficiency)
Vitamin B2 deficiency (ariboflavinosis, riboflavin deficiency)
Vitamin B6 deficiency (pyridoxine deficiency)
Vitamin B6 excess (pyridoxine excess)
Vitamin C deficiency (scurvy)
Vitamin K deficiency
Zinc deficiency

Papulosquamous hyperkeratotic
Papulosquamous hyperkeratotic cutaneous conditions are those that present with papules and scales caused by a thickening of the stratum corneum.